Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Tracing legume seed diffusion beyond demonstration trials: An exploration of sharing mechanisms
    Almekinders, Conny J.M. ; Ronner, Esther ; Heerwaarden, Joost van - \ 2020
    Outlook on Agriculture 49 (2020)1. - ISSN 0030-7270 - p. 29 - 38.
    gender - relationships - Seed diffusion - transactions

    Many interventions are assuming that introduced seeds diffuse. However, the details of this diffusion among farmers are poorly understood. This article presents data from eight sites in four on the diffusion of seed and associated information given to farmers involved in N2Africa’s demonstration trials. The study showed that 2–3 years after the trials had been organised, more than 90% of the farmers who had participating in the trial activities and were given a seed-input package with 1–5 kg of legume seed had shared this seed, on average with four other farmers. The farmers who received this seed from these directly involved farmers shared their seed less frequently. Eighty per cent of all the seed sharings were of 1–2 kg of seed given as a gift. Only 5% of the sharings involved a cash transaction. More than half of the seed sharings were with family members and around a third were between friends. Men shared at least as often as women and both men and women shared most with persons of their own sex. Information about rhizobium as an associated input for soya was shared by more than one-third of farmers, almost exclusively by farmers who had participated in the demonstration trials themselves. Extrapolation of data suggest that in addition to the 250,000 farmers who participated directly in the N2Africa demonstration trials, another 1,400,000 farmers may have received seed of a new legume crop or variety. The results show that knowing about the character of the seed sharing mechanisms may offer opportunities to influence the diffusion of seeds. Providing farmers with somewhat larger amounts of seeds, emphasise the importance of sharing seeds and information with relatives and friends could be an important factor in achieving a high multiplier effect.

    Updating the reference population to achieve constant genomic prediction reliability across generations
    Pszczola, M. ; Calus, M.P.L. - \ 2016
    Animal 10 (2016)6. - ISSN 1751-7311 - p. 1018 - 1024.
    dairy cattle - reference population - relationships - reliability

    The reliability of genomic breeding values (DGV) decays over generations. To keep the DGV reliability at a constant level, the reference population (RP) has to be continuously updated with animals from new generations. Updating RP may be challenging due to economic reasons, especially for novel traits involving expensive phenotyping. Therefore, the goal of this study was to investigate a minimal RP update size to keep the reliability at a constant level across generations. We used a simulated dataset resembling a dairy cattle population. The trait of interest was not included itself in the selection index, but it was affected by selection pressure by being correlated with an index trait that represented the overall breeding goal. The heritability of the index trait was assumed to be 0.25 and for the novel trait the heritability equalled 0.2. The genetic correlation between the two traits was 0.25. The initial RP (n=2000) was composed of cows only with a single observation per animal. Reliability of DGV using the initial RP was computed by evaluating contemporary animals. Thereafter, the RP was used to evaluate animals which were one generation younger from the reference individuals. The drop in the reliability when evaluating younger animals was then assessed and the RP was updated to re-gain the initial reliability. The update animals were contemporaries of evaluated animals (EVA). The RP was updated in batches of 100 animals/update. First, the animals most closely related to the EVA were chosen to update RP. The results showed that, approximately, 600 animals were needed every generation to maintain the DGV reliability at a constant level across generations. The sum of squared relationships between RP and EVA and the sum of off-diagonal coefficients of the inverse of the genomic relationship matrix for RP, separately explained 31% and 34%, respectively, of the variation in the reliability across generations. Combined, these parameters explained 53% of the variation in the reliability across generations. Thus, for an optimal RP update an algorithm considering both relationships between reference and evaluated animals, as well as relationships among reference animals, is required.

    Olaf van Kooten, hoogleraar Wageningen UR en lector InHolland: ‘hoezo slechte markt; we zijn zelf de markt’
    Kierkels, T. ; Kooten, O. van - \ 2014
    Onder Glas 11 (2014)8. - p. 32 - 33.
    glastuinbouw - glasgroenten - kwaliteitszorg - groenten - consumentenaangelegenheden - marketing van voedingsmiddelen - consumenten - relaties - klanttevredenheid - agrarische economie - greenhouse horticulture - greenhouse vegetables - quality management - vegetables - consumer affairs - food marketing - consumers - relationships - consumer satisfaction - agricultural economics
    Er is iets grondig mis in de afzetketen van met name groente en fruit; de samenwerking komt maar moeilijk van de grond. Als gevolg daarvan liggen er producten van een lage kwaliteit in de winkel en verdient niemand iets. Dat het anders kan bewijzen schaarse voorbeelden. Hoogleraar tuinbouwketens Olaf van Kooten van Wageningen UR vertelt het met duidelijke woorden.
    Governance of the member-cooperative relationship: a case from Brazil
    Cechin, A.D. - \ 2013
    Wageningen University. Promotor(en): Onno Omta, co-promotor(en): Jos Bijman. - S.l. : s.n. - ISBN 9789461736550 - 144
    landbouwcoöperaties - governance - kwaliteit - relaties - ketenmanagement - agro-industriële ketens - participatie - lidmaatschap - brazilië - agricultural cooperatives - governance - quality - relationships - supply chain management - agro-industrial chains - participation - membership - brazil

    Recent events in the agri-food sector increased the demand for quality attributes, from healthy and safe products to sustainable agricultural practices (Grunert, 2005). Particularly challenging is the connectedness of transactions between farmers, traders, processors, retailers and final customers in order to comply with quality requirements, which implies a need for value chain coordination. Combined with increased consumer demand for variety and convenience, these changes in sector have led to stronger sequential interdependencies, in which the output of one part is the input for another part. The increasing connectedness between transactions demands more vertical coordination. A major challenge for the agricultural cooperative is to combine horizontal coordination among the members with vertical coordination in the value chain (Bijman 2009; Hanf, 2009). Since they are member-oriented, agricultural cooperatives traditionally buy the farm products of its members regardless of its quality. Increasingly, however, cooperatives need to guarantee product quality towards their customers, and thus assure that members supply products of the right quality.

    The objective of this thesis is to disentangle the governance mechanisms that can be used by the cooperative to strengthen the member-cooperative relationship, and to assess the impact of the different governance mechanisms on the coordination of members’ adjustments to higher quality levels. The attempt to organize the participating farmers and firms along the food value chain generates transactional risks and coordination costs in the relationship between agricultural cooperative and farmer-member. This leads to the first research question of this thesis.

    R.Q. (1): What are the mechanisms for governing the member-cooperative relationship, and how do they affect transactional risks and coordination costs?

    This thesis (Chapter 2) poses that four governance mechanisms - market, hierarchy, community and democracy affect coordination costs and transactional risks through their effect on member commitment and cognitive heterogeneity. It is important that members of an agricultural cooperative are committed to customer orientation; otherwise the involved transactional risks would make vertical coordination more costly. It is necessary to disentangle two types of commitment: to collective action and to customer orientation. Member commitment to collective action prevents side selling, in particular, and free-riding behaviour in general. This leads to the second research question of this thesis.

    R.Q. (2): How do the four governance mechanisms - market, hierarchy, community and democracy - affect both types of commitment?

    One of the conclusions stemming from this thesis was that, on the one hand, a cooperative may assure members’ compliance in a less costly way if market incentives related to quality, productivity and effort are strengthened, as well as (hierarchy) input control and on-farm monitoring, since these mechanisms are positively related to commitment to customer orientation. On the other hand, democracy and community mechanisms do have an important role in enhancing commitment to collective action which is a sine qua non condition for the viability of the cooperative (Chapter 3).

    A large multi-product cooperative in which different activities of the cooperative cater to different groups of members, as the case that was chosen as the empirical basis of this thesis, may face problems related to membership heterogeneity (Hansmann, 1996; Fulton and Giannakas, 2001). The basic assumption in most of the literature on the impact of member heterogeneity on the process and outcomes of decision-making is that farmers pursue individual or subgroup interests when participating in the decision-making of the cooperative. If members primarily pursue individual economic interests, there might be a relationship between the economic reasons for becoming a member (and maintaining membership) and the motivation to participate in the governance of the cooperative. This leads to the third research question of this thesis.

    R.Q. (3): How do economic motivations for association affect members’ participation in the governance of a cooperative?

    The conclusion of this thesis, regarding this research question, was that besides the role of social mechanisms in enhancing commitment to collective action, there seems to be a role of social mechanisms in enhancing members’ control of their cooperative. Members who participate in boards or committees are not actuated to participate by the same economic motivations that drive their association to the cooperative. Cooperative ideology, in turn, appears to be an important motivation for them to actively participate (Chapter 4).

    The ability of cooperatives to adapt to a rapidly changing environment characterized by technological change and industrialization of agriculture has been questioned Fulton (1995). The organizational structure of the cooperative is said to have negative implications for its quality management (Mérel et al., 2009). On the one hand, cooperatives may be mimicking Investor-Owned Firms (IOFs) in applying more hierarchical mechanisms which enable them to define and effectively apply quality norms for their supply, control the quality of delivered products and monitor members’ production processes. On the other hand, cooperatives have unique organizational characteristics that could provide them with competitive advantage, such as the tight relationship between members and cooperative, which may enable less costly coordination of the transaction (Sykuta and Cook, 2001). This leads to the fourth and last research question of this thesis.

    R.Q. (4): What are the differences in quality performance between a cooperative and an IOF, and can these differences be explained by relationship characteristics?

    In the Brazilian broiler industry, suppliers delivering to a cooperative are performing better in terms of quality than suppliers delivering to an IOF. Cooperative and IOF have the same incentive and control mechanisms for production efficiency and high-quality chicken meat. The cooperative’s advantage over the IOF in terms of suppliers’ quality performance could be influenced by the characteristics of the supplier-buyer relationship. This thesis shows (Chapter 5) that there are some important differences regarding relationship characteristics that could account for this higher performance. Dependence on current buyer, which is higher for cooperative members, uncertainty regarding buyer’s behavior, which is lower for cooperative members, and market risk reduction by the buyer, which is higher for cooperative members, can help explain the higher rate of compliance to the “feet callus” quality standard. These three features of the supplier-cooperative relationship are likely to prevent suppliers from shirking behavior and to induce commitment. Moreover, cooperative suppliers receive more technical support from their buyer for adapting to new quality requirements than IOF suppliers do; this is likely to positively affect farmers’ competence in complying with quality standards.

    The main methodological approach of this thesis is quantitative. Qualitative data were collected through semi-structured interviews with professional managers of the industrial division, directors and farmers in order to guide the design of the questionnaire. The data that is analyzed in this thesis were collected by using a survey questionnaire applied among 148 farmers, all members of the same multi-product cooperative in Brazil, and 42 broiler suppliers of two major buyers in the same region.

    This thesis makes several theoretical contributions, which can be listed as follows:

    (1) Member commitment in agricultural cooperatives can be disentangled conceptually and empirically into two types. Commitment to collective action is related to Fulton’s (1995) definition: the willingness to patronize a cooperative even when the cooperative’s price or service is not as good as that provided by an IOF. It is an attitude that precedes loyal behaviour; it is the making of a sacrifice or an effort in the name of the relationship and the success of the organization. Commitment to customer orientation, in turn, is the willingness to give up a part of the autonomy at the farm level for the sake of the cooperative’s compliance with the requirements from downstream customers. It is a positive attitude of members towards the re-orientation of the cooperative and is related to Borgen’s (2001) view on commitment.

    (2) Membership heterogeneity might not be a source of inefficiency in decision-making if the organizational goal is precisely to satisfy diverse members’ interests, and if members who occupy representative and managing functions are genuinely seeking to further organizational goals rather than to follow private motives. Most conceptualizations of decision-making problems and influence costs derive from organizational economics, where agency theory has been quite influential. The findings of this thesis (Chapter 4) suggest that assumptions from agency theory, which are often adopted by cooperative studies, could better be treated as an empirical matter.

    (3) This thesis presents a different perspective on the comparative advantage of the cooperative in producing food products with higher quality attributes. The literature on the implications of the cooperative structure for quality management (Mérel et al., 2009) emphasizes that cooperatives often fail to adequately reward the highest quality producers, often causing the problem of “adverse selection”. However, despite starting with larger heterogeneity in terms of producers’ capacity to produce high-quality products, cooperatives may achieve high quality products through superior coordination and adaptation support. The findings of this thesis are in line with other empirical studies outside the domain of cooperatives that found that quality performance may be influenced by relationship characteristics, through their effect on transaction costs (Lu et al., 2009; Coronado et al., 2010).

    (4) Overall, the main scientific contribution of this thesis is the use of the ‘chemistry of organizations’ framework proposed by Grandori and Furnari (2008) in seeking a better understanding of the governance of cooperatives. By adopting that framework the thesis addressed in an integrated way the role of social capital (Ostrom, 1999) and community governance (Bowles and Gintis, 2002; Hayami, 2009) in facilitating collective action, and the role of relational contracts (Poppo and Zenger, 2002; Lazzarini, Miller and Zenger, 2004) in assuring commitment from parties in a transaction. Furthermore, with that framework, the thesis addressed the cognitive role of governance mechanisms, such as knowledge exchange (Conner and Prahalad, 1996; Grant, 1996) and competence enhancing (Nooteboom, 2004).

    The implications of this thesis for management and policy are listed in the three following groups:

    (1) Rewarding farmers appropriately and controlling and monitoring delivery and production processes are important for enhancing commitment both to collective action and to customer orientation. Giving “voice” and building a social community for members and their families are important to prevent members’ free-riding and selling “outside”. It is advised to combine at least the following governance mechanisms: hierarchy control, market incentives, community involvement and democratic voice. Finally, communication is an important tool for enhancing farmers’ commitment to customer orientation.

    (2) Cooperatives can participate in high-quality value chains and be as efficient and effective as other organizational arrangements in the agri-food sector. More importantly, cooperatives might even have an advantage in the production and marketing of goods with credence attributes, such as animal welfare, organic and fair trade. Therefore, policies aiming to promote sustainable food production may target cooperatives, as this organisational form is more effective in lowering the risks associated with farmer’ opportunistic behavior.

    (3) Member participation, commitment, satisfaction with leadership and with the cooperative’s strategy are examples of what could be additional performance criteria besides reported profits, which taken alone could be misleading. Because the cooperative’s objectives are beyond the economic viability of the collective enterprise, (Birchall and Ketilson, 2009), the intangible social assets should be assessed in order to evaluate the performance of the cooperative, and thereby to compare cooperatives with investor-owned firms and among cooperatives themselves.

    Inter-organizational information exchange, supply chain compliance and performance
    Peng, G. - \ 2011
    Wageningen University. Promotor(en): Onno Omta, co-promotor(en): Jacques Trienekens. - [S.l.] : S.n. - ISBN 9789085859529 - 220
    business management - supply chain management - communication - cooperation - businesses - relationships - governance - performance - improvement - information - bedrijfsmanagement - ketenmanagement - communicatie - samenwerking - bedrijven - relaties - governance - prestatieniveau - verbetering - informatie
    In modern business management today's companies no longer compete as solely autonomous entities, but rather as supply chains. Supply chain collaboration can bring with substantial benefits and advantages for companies. To strenghten supply chain collaboration, inter-organisational communication is an essential enabler.
    Gender, AIDS and food security : culture and vulnerability in rural Côte d'Ivoire
    Maiga, M.M. - \ 2010
    Wageningen University. Promotor(en): Leontine Visser; Anke Niehof. - [S.l. : S.n. - ISBN 9789085857891 - 199
    acquired immune deficiency syndrome - voedselzekerheid - cultuur - plattelandsvrouwen - sociologie - vrouwelijke arbeidskrachten - plattelandsbevolking - sociale economie - verwantschap - relaties - ivoorkust - afrika - geslacht (gender) - strategieën voor levensonderhoud - acquired immune deficiency syndrome - food security - culture - rural women - sociology - female labour - rural population - socioeconomics - kinship - relationships - cote d'ivoire - africa - gender - livelihood strategies
    Bos op arme gronden
    Kint, Vincent ; Geudens, Guy ; Ouden, J. den - \ 2010
    In: Bosecologie en Bosbeheer / den Ouden, J., Muys, B., Mohren, G.M.J., Verheyen, K., Leuven : ACCO - ISBN 9789033477829 - p. 511 - 526.
    zandgronden - bossen - relaties - eolische afzettingen - bodem-plant relaties - vlaanderen - sandy soils - forests - relationships - aeolian deposits - soil plant relationships - flanders
    Onder arme groeiplaatsen worden vooral de zandgronden verstaan. In Nederland liggen ze in het oosten en het zuiden van het land en ze lopen door naar de zandgronden in het noorden van Vlaanderen. De duinengordel langs de Noordzeekust behoort ook tot deze categorie. Zandgronden kunnen verder ingedeeld worden volgens hun geologische ontstaanswijze. Er kan onderscheid gemaakt worden tussen afzettingen door zee, rivieren of de wind, die bovendien uit het tertiair of het quartair tijdvak kunnen dateren. Zowel in Vlaanderen als Nederland ligt het grootste deel van het huidige bosareaal op de arme zandgronden: in Vlaanderen is het 60% van het totale areaal (90.000 ha) en in Nederland 86% (270.000 ha).
    Eerste resultaten onderzoek naar meest geschikte ras-onderstamcombinaties
    Maas, F.M. ; Beurskens, Stan - \ 2009
    De Wijngaard 17 (2009)2. - p. 29 - 30.
    druiven - rassen (planten) - relaties - onderstammen - stamverschillen - wijndruivenrassen - bodemtypen - landbouwkundig onderzoek - nederland - grapes - varieties - relationships - rootstocks - strain differences - wine cultivars - soil types - agricultural research - netherlands
    In 2008 is in samenspraak met het Wijngaardiersgilde en met subsidie van het ministerie van LNV een onderzoek gestart om verspreid over Nederland en voor verschillende bodemtypen te onderzoeken hoe de verschillende druiven ras-onderstamcombinaties zich ontwikkelen. 14 Rode en 14 witte druivenrassen staan op 9 verschillende bedrijven op 9 verschillende onderstammen. Dit eerste jaar zijn al grote verschillen per regio en per bedrijf gemeten, volgende 2 jaren zal het onderzoek zich toespitsen op de verschillen in groei, loofwandstructuur, gewasgezondheidsaspecten, oogsttijdstippen en de oogstgegevens.
    Internationaal belang van de nationale natuur : ecosystemen, vaatplanten, mossen, zoogdieren, reptielen, amfibieën en vissen
    Janssen, J.A.M. ; Stumpel, A.H.P. ; Bijlsma, R.J. ; Hennekens, S.M. ; Keizer-Sedlakova, I. ; Kuiters, A.T. ; Ottburg, F.G.W.A. ; Ozinga, W.A. ; Schaminée, J.H.J. ; Siebel, H.N. - \ 2007
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-rapport 43) - 54
    ecosystemen - natuurbescherming - bedreigde soorten - beschermde soorten - soorten - nederland - relaties - europa - natuurbeleid - ecosystems - nature conservation - endangered species - protected species - species - netherlands - relationships - europe - nature conservation policy
    In dit rapport wordt een analyse uitgevoerd van de ecosystemen en soorten (uit een beperkt aantal soortsgroepen) waarvoor ons land internationale verantwoordelijkheid draagt. Hierbij worden een vijftal criteria toegepast: aandeel areaal, aandeel populatie of oppervlakte, ligging ten opzichte van het areaal, voorkomen op internationale rode lijst en – voor ecosystemen en trekvissen – een specifieke reden. Uit de analyse komen 34 ecosystemen en 111 soorten naar voren waarvoor Nederland binnen Europa van groot belang is. Bekeken is voorts in welke landschappen de internationaal belangrijke ecosystemen en soorten voorkomen en in hoeverre ze aandacht krijgen in het nationale en internationale natuurbeleid. De belangrijkste landschappen met de internationaal belangrijke ecosystemen en soorten zijn de hogere zandgronden en het kustgebied, gevolg door het rivierengebied en het laagveen. In het internationale natuurbeleid (Habitatrichtlijn) krijgen vier van de resulterende ecosystemen onvoldoende aandacht, in het nationale beleid komen vooral de mossen er bekaaid af. Trefwoorden: Natuurbeleid, internationaal, ecosystemen, soorten, Europa
    The role of guanxi in buyer-seller relationships in China : a survey of vegetable supply chains in Jiangsu Province
    Lu Hualiang, - \ 2007
    Wageningen University. Promotor(en): Onno Omta, co-promotor(en): Jacques Trienekens. - [S.l.] : S.n. - ISBN 9789085046653 - 252
    food chains - vegetables - marketing - production - china - trade - markets - businesses - relationships - socioeconomics - supply chain management - agro-industrial chains - networks - social capital - voedselketens - groenten - marketing - productie - china - handel - markten - bedrijven - relaties - sociale economie - ketenmanagement - agro-industriële ketens - netwerken - sociaal kapitaal
    Keywords:Social capital,guanxinetworks, vegetable supply chains, buyer-seller relationships, channel performance,China

    Guanxiis ubiquitous inChinaand significantly influences people's behaviour in social life and in business. Guanxi refers to personal relationships or connections and is widely recognised as a Chinese form of social capital. This book focuses on the questions, if, and if so, how small-scale producers, together with processors and exporters, can be more successfully integrated into high-value supply chains (i.e., processors, supermarkets and international markets). In particular, our focus is on how Chinese vegetable farmers can use their guanxi networks to be integrated into these modern supply chains and can improve their market performance. We study the effectiveness of both formal (contracts) and relational ( guanxi ) governance mechanisms to improve the integration of buyer-seller relationships and ultimately, to enhance chain performance. We apply various theoretical approaches, supply chain management, social capital theory and transaction cost economics, to develop propositions regarding the interrelation of support from guanxi networks (what guanxi can do for you), buyer-seller relationships (interpersonal trust, transaction specific investments and contractual governance) and market performance (compliance with delivery/quality requirements, efficiency, quality/price satisfaction, and profitability). We combine case study with survey analysis and use structural equation modelling techniques to test the propositions.

    Background analysis of the Chinese vegetable sector indicates that small-scale farmers usually fail to integrate into high-value market outlets. This is because these farmers face several constraints, such as small production scale, less possibilities to implement quality standards, low negotiation power, and information asymmetry. However, empirical analysis based on three different buyer-seller relationships, including farmers, processors and exporters/supermarkets, shows that support from guanxi networks and integration of buyer-seller relationships significantly contribute to market performance (especially with downstream partners). The effects of guanxi networks differ between primary producers, processors and exporters/supermarkets, and across marketing channels. Vegetable farmers and their buyers show an idiosyncratic way to rely on their guanxi networks in doing business. Furthermore, vegetable farmers and their buyers follow different approaches to achieve market performance. Interpersonal trust and compliance with delivery requirements are important factors for all parties in supply chains to achieve superior performance. Particularly, in relationships with downstream partners, the sellers tend to rely on their guanxi networks when conducting transactions. In relationships with upstream partners, guanxi networks and contractual governance are less often used. This study shows that the combination of formal (contract) and informal ( guanxi ) governance mechanisms seems to be the best way to improve chain performance in vegetable supply chains inChina. Policy should be directed to improve farmers' capacity to participate in modern high-value markets as well as to enhance the prospects forChina's vegetables in the world.
    Female livelihoods and agrarian changes in Indonesia
    Oosterhout, D.W.J.H. van - \ 2006
    social anthropology - food - social structure - kinship - relationships - society - feeding habits - behaviour - south east asia
    Ketenomkering in kennisland
    Wals, A.E.J. ; Lans, T. ; Buurma, J.P. - \ 2005
    Gewasbescherming 36 (2005)suppl. - ISSN 0166-6495 - p. 7 - 9.
    kennis - verspreiding van onderzoek - netwerken (activiteit) - onderzoeksinstituten - technologieoverdracht - informatieverspreiding - onderzoeksimplementatie - onderzoek - onderwijs - particuliere sector - relaties - knowledge - diffusion of research - networking - research institutes - technology transfer - diffusion of information - implementation of research - research - education - private sector - relationships
    Themavoordracht waarin twee manieren van kennismobiliteit worden besproken: de doorstromingsrelatie, waarbij kennis wordt gezien als product en doorstroomt van onderzoeksinstituten naar onderwijs en de netwerkrelatie, waarbij kennis wordt gezien als proces tussen onderzoek, onderwijs en bedrijfsleven
    Livelihood and food security in rural Bangladesh- the role of social capital
    Ali, A. - \ 2005
    Wageningen University. Promotor(en): Anke Niehof. - Wageningen : - ISBN 9789085042969 - 264
    voedselzekerheid - levensomstandigheden - relaties - gemeenschappen - samenleving - menselijke relaties - man-vrouwrelaties - huishoudens - inkomen - platteland - levensstandaarden - vrouwen - Bangladesh - positie van de vrouw - sociale relaties - vrouw en samenleving - arbeid in de landbouw - strategieën voor levensonderhoud - food security - living conditions - relationships - communities - society - human relations - gender relations - households - income - rural areas - living standards - women - Bangladesh - woman's status - social relations - woman and society - farm labour - livelihood strategies
    This thesis describes the role of social capital of households and individuals in achieving livelihood and food security. In the research the temporal dimension and gender were cross-cutting perspectives. IFPRI panel data collected during 1996-1997 (pre-flood) and 1999-2000 (post-flood) were analyzed. To complement the IFPRI data an additional survey and the qualitative data was collected during 2001-2003. Panel data analysis shows that gender of the household head does not make a difference in achieving food security at the household level. However, gender of the household member is crucial for attaining individual level food security. Social capital plays an important role in averting vulnerability and sustaining livelihood, and is influenced by the landholding status of the house hold, which seems to function as collateral. The qualitative data revealed that women's social capital, when defined in a broader way, does play a crucial role in achieving household food security and averting vulnerability.
    The hillslope-storage Boussinesq model for variable bedrock slope
    Hilberts, A.G.J. ; Troch, P.A.A. ; Loon, E.E. van; Paniconi, C. - \ 2004
    regen - oppervlakkige afvoer - relaties - infiltratie - glooiend land - modellen - rain - runoff - relationships - infiltration - sloping land - models
    Managing business networks and buyer-supplier relationships. How information obtained from the business network affects trust, transaction specific investments, collaboration and performance in the Dutch Potted Plant and Flower Industry
    Claro, D.P. - \ 2004
    Wageningen University. Promotor(en): Onno Omta, co-promotor(en): Geoffrey Hagelaar; D. Zylbersztajn. - Veenendaal : Universal Press - ISBN 9789058089465 - 196
    bedrijven - relaties - potplanten - bloemen - informatie - nederland - productie - aanbod - landbouwindustrie - ketenmanagement - netwerken - bedrijfseconomie - businesses - relationships - pot plants - flowers - production - supply - agribusiness - information - netherlands - supply chain management - networks - business management
    Managing networks and buyer-supplier relationships " attempt to provide scientific sound discussion for problems faced in business linkages. Business networks, supply chains and buyer-supplier relationships all refer to business linkages, from a web of connected relationships to a dyadic relationship. At the beginning of our study, we were triggered by the impact of the business network on collaborative, long-term buyer-supplier relationships. In other words, does the information a company obtains from the network support the buyer-supplier relationship? In fact, yes. Our study provides a theoretical framework and empirical evidence that will assist practitioners in the management of their business network and buyer-supplier relationships. The empirical evidence was gathered on the basis of two constructive steps, namely case study and survey. Buyers and suppliers in the Dutch potted flower and plant industry offered valuable insights to estimate statistical models. The involvement of buyers and suppliers allowed discussions from both sides of the relationship - purchasing and marketing.

    This thesis is aimed at managers at different levels in firms, which includes every decision maker in purchasing, selling or strategic planning levels. Policy makers and researchers in the field of supply chain and network management may also find useful ideas and concepts in our theoretical framework. Researchers in the fields of relationship management may be particularly interested in theoperationalizationsof the conceptual elements of the framework and the interpretation of the estimated statistical models.

    The Emerging World of Chains and Networks, Bridging Theory and Practice
    Camps, Th. ; Diederen, P.J.M. ; Hofstede, G.J. ; Vos, B. - \ 2004
    Amsterdam : Reed Business Information - ISBN 9789059019287 - 348
    innovaties - bedrijfsvoering - relaties - informatie - ketenmanagement - netwerken - productieprocessen - management - relationships - innovations - information - supply chain management - networks - production processes
    Bodem, humus en vegetatie onder verschillende loofboomsoorten op de stuwwal bij Doorwerth
    Hommel, P.W.F.M. ; Waal, R.W. de - \ 2004
    Wageningen : Alterra (Alterra-rapport 920) - 66
    bossen - vegetatie - humus - tilia - ligstro - bosgronden - plantensuccessie - nederland - relaties - veluwe - bodem-plant relaties - natuurgebieden - forests - vegetation - humus - tilia - litter - forest soils - plant succession - netherlands - relationships - veluwe - soil plant relationships - natural areas
    Dit rapport gaat in op de relatie tussen loofboomsoort, humus en ondergroei op een zwak lemige stuwwalbodem bij Doorwerth (Gelderland). Er werden opstanden vergeleken van linde, esdoorn, haagbeuk, eik en beuk. Onder invloed van het `rijke¿, goed verterende bladstrooisel van linde, esdoorn en haagbeuk bleek een ontwikkeling in de richting van een `rijker¿ bostype op gang te zijn gekomen. Alleen onder linde was echter binnen 40 jaar een goed ontwikkelde, soortenrijke Carpinion-vegetatie met meerdere oud-bossoorten ontstaan. De vegetatieontwikkeling onder linde lijkt wel sterk afhankelijk te zijn van de hoeveelheid licht die tot de bosbodem weet door te dringen.
    Hillslope-storage Boussinesq model for subsurface flow and variable source areas along complex hillslopes: 2. Intercomparison with a three-dimensional Richards equation model
    Paniconi, C. ; Troch, P.A.A. ; Loon, E.E. van; Hilberts, A.G.J. - \ 2003
    Water Resources Research 39 (2003)11. - ISSN 0043-1397 - p. 1317 - 1317.
    regen - oppervlakkige afvoer - relaties - infiltratie - hydrologie van stroomgebieden - modellen - rain - runoff - relationships - infiltration - catchment hydrology - models - free-surface flow - capillarity correction - runoff generation - rainfall - soils - groundwater - scale
    The Boussinesq equation for subsurface flow in an idealized sloping aquifer of unit width has recently been extended to hillslopes of arbitrary geometry by incorporating the hillslope width function w(x) into the governing equation, where x is the flow distance along the length of the hillslope [ Troch et al., 2003 ]. Introduction of a source/sink term N allows simulation of storm-interstorm sequences in addition to drainage processes, while a function S c (x) representing the maximum subsurface water storage can be used to account for surface saturation response in variable source areas activated by the saturation excess mechanism of runoff generation. The model can thus simulate subsurface flow and storage dynamics for nonidealized (more realistic) hillslope configurations. In this paper we assess the behavior of this relatively simple, one-dimensional model in a series of intercomparison tests with a fully three-dimensional Richards equation model. Special attention is given to the discretization and setup of the boundary and initial conditions for seven representative hillslopes of uniform, convergent, and divergent plan shape. Drainage and recharge experiments are conducted on these hillslopes for both gentle (5%) and steep (30%) bedrock slope angles. The treatment and influence of the drainable porosity parameter are also considered, and for the uniform (idealized) hillslope case the impact of the unsaturated zone is examined by running simulations for different capillary fringe heights. In general terms, the intercomparison results show that the hillslope-storage Boussinesq model is able to capture the broad shapes of the storage and outflow profiles for all of the hillslope configurations. In specific terms, agreement with the Richards equation results varies according to the scenario being simulated. The best matches in outflow hydrographs were obtained for the drainage experiments, suggesting a greater influence of the unsaturated zone under recharge conditions due to transmission of water throughout the hillslope. In the spatiotemporal water table response a better match was observed for convergent than divergent hillslopes, and the bedrock slope angle was not found to greatly influence the quality of the agreement between the two models. On the basis of the intercomparison experiments we make some suggestions for further development and testing of the hillslope-storage model
    Hillslope-storage Boussinesq model for subsurface flow and variable source areas along complex hillslopes: 1. Formulation and characteristic response
    Troch, P.A.A. ; Paniconi, C. ; Loon, E.E. van - \ 2003
    Water Resources Research 39 (2003). - ISSN 0043-1397 - p. 1316 - 1316.
    regen - oppervlakkige afvoer - infiltratie - hellingen - relaties - modellen - hydrologie van stroomgebieden - rain - runoff - relationships - infiltration - slopes - models - catchment hydrology - watershed thermodynamics - unifying framework - soil-moisture - variability - catchment - hydrology - equation - terrain
    Hillslope response to rainfall remains one of the central problems of catchment hydrology. Flow processes in a one-dimensional sloping aquifer can be described by Boussinesq's hydraulic groundwater theory. Most hillslopes, however, have complex three-dimensional shapes that are characterized by their plan shape, profile curvature of surface and bedrock, and the soil depth. Field studies and numerical simulation have shown that these attributes are the most significant topographic controls on subsurface flow and saturation along hillslopes. In this paper the Boussinesq equation is reformulated in terms of soil water storage rather than water table height. The continuity and Darcy equations formulated in terms of storage along the hillslope lead to the hillslope-storage Boussinesq (HSB) equation for subsurface flow. Solutions of the HSB equation account explicitly for plan shape of the hillslope by introducing the hillslope width function and for profile curvature through the bedrock slope angle and the hillslope soil depth function. We investigate the behavior of the HSB model for different hillslope types (uniform, convergent, and divergent) and different slope angles under free drainage conditions after partial initial saturation (drainage scenario) and under constant rainfall recharge conditions (recharge scenario). The HSB equation is solved by means of numerical integration of the partial differential equation. We find that convergent hillslopes drain much more slowly compared to divergent hillslopes. The accumulation of moisture storage near the outlet of convergent hillslopes results in bell-shaped hydrographs. In contrast, the fast draining divergent hillslopes produce highly peaked hydrographs. In order to investigate the relative importance of the different terms in the HSB equation, several simplified nonlinear and linearized versions are derived, for instance, by recognizing that the width function of a hillslope generally shows smooth transition along the flow direction or by introducing a fitting parameter to account for average storage along the hillslope. The dynamic response of these reduced versions of the HSB equation under free drainage conditions depend strongly on hillslope shape and bedrock slope angle. For flat slopes (of the order of 5%), only the simplified nonlinear HSB equation is able to capture the dynamics of subsurface flow along complex hillslopes. In contrast, for steep slopes (of the order of 30%), we see that all the reduced versions show very similar results compared to the full version. It can be concluded that the complex derivative terms of width with respect to flow distance play a less dominant role with increasing slope angle. Comparison with the hillslope-storage kinematic wave model of Troch et al. [2002] shows that the diffusive drainage terms of the HSB model become less important for the fast draining divergent hillslopes. These results have important implications for the use of simplified versions of the HSB equation in landscapes and for the development of appropriate analytical solutions for subsurface flow along complex hillslopes
    De betekenis van landbouwhuisdieren in de hulpverlening : resultaten van interviews met professionals op zorg- en kinderboerderijen
    Hassink, J. - \ 2002
    Wageningen : Plant Research International - 50
    vee - mens - relaties - psychosociale aspecten - psychotherapie - jeugdzorg - beperkingen - risicoschatting - nederland - schoolboerderijen - zorgboerderijen - livestock - man - relationships - psychosocial aspects - psychotherapy - child welfare - risk assessment - netherlands - labour - school farms - social care farms
    Veranderingen in mens-dierrelaties en hun impact op de veehouderij van 2040
    Ketelaar-de Lauwere, C.C. ; Blokhuis, H.J. ; Dagevos, H. ; Ipema, A.H. ; Stegeman, J.A. - \ 2000
    Wageningen : IMAG (Rapport / IMAG 2000-6) - ISBN 9789067546096 - 52
    relaties - dieren - mens - dierhouderij - dierenwelzijn - biotechnologie - biologische landbouw - innovaties - relationships - animals - man - animal husbandry - animal welfare - biotechnology - organic farming - innovations
    Irrigating lives : development intervention and dynamics of social relationships in an irrigation project
    Magadlela, D. - \ 2000
    Agricultural University. Promotor(en): N.E. Long. - S.l. : S.n. - ISBN 9789058081575 - 294
    ontwikkelingsprojecten - irrigatie - ontwikkeling - interventie - plattelandsontwikkeling - sociale verandering - sociale interactie - relaties - dynamica - sociologie - zimbabwe - development projects - irrigation - development - intervention - rural development - social change - social interaction - relationships - dynamics - sociology - zimbabwe

    This study is about rural agricultural development and social processes of change in rural Zimbabwe. It is aimed at understanding how irrigation intervention in a remote rural context changed the cultural, social, political and farming lives of people. It is a study of people coping with changes in their livelihoods which had been introduced from outside by development intervention. The study was sustained by the realisation that irrigation is not just a matter of technical artefacts, but has much to do with people, especially the people it is meant to benefit. Development practitioners and researchers should be interested not only in irrigation performance, but also in how people manipulate the irrigation resources available to them. How does irrigation development change the lives of the irrigators over time? How is it transformed and adapted by them? How does it change their perceptions of each other in view of their local social identities and differences? What do irrigation farmers use to gain improved access to irrigation resources? How do they manipulate their social, political, technical and management environments to their benefit? What lessons can we derive from "targeted" beneficiaries' analyses of how their lives have been transformed by development intervention?

    The study focuses on social constructions of cultural identities, on social interaction and change among smallholder farmers in the context of irrigation development intervention in Eastern Zimbabwe. It shows how the introduction of an irrigation scheme not only created, but also nurtured and promoted processes of cultural identity and social differentiation among groups of rural producers who had previously had but few distinguishing social characteristics (such as ethnic affiliation). It is a study of how the irrigation context helps to highlight their social and cultural differences and leads to social conflicts and leadership struggles, and to how different individual actors devise strategies, such as enrolling outsiders into local struggles, to achieve their often conflicting group and individual objectives. The analysis portrays the irrigation scheme as a social and political 'domain' in which different groups of farmers and outsiders engage each other in negotiations over resources, and the meanings attached to these resources. In some instances, the irrigation domain is seen as an arena, a contested area where struggles take place over a diversity of livelihood resources such as water and land.

    The study used the actor-oriented perspective as the theoretical basis for the analysis of research findings. An actor-oriented approach helps one recognise the agency of social actors in interactive situations. It requires a full analysis of the ways in which different social actors manage and interpret new elements in their life-worlds. The capacity of social actors to influence and shape their social surroundings is one of the salient features of the approach used in this Nyamaropa study.

    The study is also about the omnipresence of encounters and clashes of different 'world-views' at the local level in the irrigation scheme. The clashes take place in the social, technical, administrative, managerial and political domains. It looks at how the different 'life-worlds' accommodate to each other in actors' daily interactions to give a semblance of harmony and attraction, co-existing with conflict and rejection. It is an analysis of the dynamism of social differences in irrigation intervention, and in any development intervention for that matter, that reveals the multiplexity of actors' interactions, and how their multiple relations and interlocking projects generate potentially explosive social exchanges. The study starts from the bottom, as it were, in its analysis of how different people in a specific rural development context create and live with complex social relations where daily interaction is characterised by strategic negotiation and mutual enrolment in other actors' projects. The analysis focuses more on local level dynamics, and does not deal, for example, with the politics of decision-making at higher levels of administration, such as the province or central government departments under which smallholder irrigation development falls. The study does, however, acknowledge the inevitable, sometimes useful role of macro-policy structures in influencing development outcomes at the local level.

    As a sociological study, this research work focused on how people interacted, worked together, settled differences and used community resources in their daily struggles for survival. Irrigation literature in Zimbabwe has only recently begun to pay specific attention to the fact that irrigation development is essentially a social process. Part of the objective here is to contribute to the debate about how rural actors manage their differentiated irrigating lives, discourses, struggles and negotiations, conflicts and accommodations in their constantly changing social environments. In order to examine this complex social process, it was proposed to undertake a detailed analysis of one irrigation scheme and its impact both on farmers practising irrigated agriculture and on surrounding dryland communities.

    The thesis is divided into four parts. Part One gives 'the story behind the study'. Then there is a background to the study in the form of Chapter 2. This chapter provides what I have called The Setting. This is Zimbabwe's agricultural history, the history of smallholder irrigation development in the country, a background to Nyamaropa irrigation intervention, and an introduction to the different social and political actors who appear throughout the book.

    Part Two is about the embeddedness of social, political and power relationships, social and economic differences, in land and water resources. Chapter 3 deals with struggles over land and water among irrigation farmers. There is a debate on water ownership from the different actors' standpoints in the Nyamaropa area. This chapter is central in the sense that it introduces the crucial issues of cultural and social identity in relations between formal irrigators and non-irrigators, between original inhabitants of the now irrigated area and immigrants to the same area. These are some of the issues that set the scene for case analyses of the dynamics of development intervention, constructions and reconstructions of cultural and social identities and differences.

    Chapter 4, also in Part Two, is about the issue of different claims to water use, between irrigation farmers in the Nyamaropa project, and villagers in the catchment area who use river water which is the source of water for the irrigation scheme downstream. Here the argument is that spatial distinctions, cultural identities, and a strong sense of communal existence, constitute a crucial entry point for the analysis of ways of assembling claims to resource use by different actors. Differences in community organisation feature as competing aspects of claims to resource utilisation.

    Part Three is about the irrigation domain as a shared life-world. Chapter 5 is on gender images and irrigation life. There are cases of widows who struggle to survive in a tough and competitive irrigation environment. A salient feature of this chapter is how women relate to the irrigation scheme through their families or individual plots. Walking through the irrigation scheme one is struck by a common feature of the area: over seventy percent of people one sees working or meets in the fields are women and children, with the majority of them being women. A surprising, yet refreshing, phenomenon in the Nyamaropa irrigation scheme is that almost thirty percent of registered plotholders are widows! Some of them registered as widows when their men worked in town, so that they would have access to irrigated plots. This was a stratagem to beat the rule prohibiting those with wage-earning spouses from having access to irrigated land. It worked, to their advantage.

    Chapter 6 focuses on irrigation extension specifically. This provides cases of farmers' encounters with Agritex (the national extension agency), and reveals the different views of similar situations between farmers and outsiders, and among farmers themselves in the presence of outsiders. This chapter focuses on one of the central issues in the study: that of how social differences among people impact on their responses to new knowledge and information. In this case, it is a matter of how farmers relate to Extension Workers as promoters of change, improvement and innovation.

    Part Four is on official (and unofficial) regulations and practices, looking especially at government practice through Agritex and the traditional institution through the Headman. Chapter 7 deals with a delicate and sensitive subject of age, inheritance, sub-leasing and renting, and the irrigation rules which were ignored. The average age of plotholders in Nyamaropa was approximately 55 years, though there were plotholders as old as 84 years. Most of them were first generation plotholders. These were farmers who cleared the plots themselves when the project started in the late fifties. Most of the elderly irrigators were too old to fully utilise their irrigation plots, but still retained their names in the register. They regarded irrigation land as their family asset, against the official rule that they were lessees on state land. To maintain productivity, they sub-leased their plots to dryland farmers who needed irrigated land for food. Some of them had established networks with local businessmen who rented part of their land in return for paying irrigation fees for the plotholders. There were some long-term relationships of mutual assistance between the different types of farmers. Rules and regulations are seen here as among the tools at farmers' disposal in their constant negotiations for 'better deals' among themselves and with their resident Extension Workers.

    Chapter 8 is the only chapter in Part Five. This section provides conclusions and theoretical analyses of research findings. It contextualises social difference and cultural identity in the life-situations of irrigators and drylanders in Nyamaropa. Discussed here are issues of how the different social groupings fit into the whole story of social dynamics of development intervention, and what some social theorists say on the issue of cultural identity and social difference (which is not much so far). This chapter brings together different theoretical issues raised in case material in the chapters before it. Chapter 8 also looks into problems facing 'irrigating lives' in smallholder irrigation schemes in the context of external intervention, and the issues and contradictions surrounding concepts such as cultural identity, and strategic difference in rural development.

    One hopes that such a study will initiate a process that will lead to bringing out and appraising differences among development programme beneficiaries to make interventions not merely effective (by externalised criteria), but also meaningful to the range of people whose lives are unavoidably affected by its introduction. The study will help in the general understanding of social dynamics of rural development, of land reform and of poverty-reduction strategies in Zimbabwe and the Southern African region.

    Trekkers naast de trap : een zoektocht naar de dynamiek in de relatie tussen boer en overheid
    Hees, E. - \ 2000
    Agricultural University. Promotor(en): J.D. van der Ploeg; J. de Vries. - S.l. : S.n. - ISBN 9789058083234 - 181
    boeren - regering - relaties - landbouwbeleid - belangengroepen - nederland - verhoudingen tussen bevolking en staat - farmers - government - relationships - interest groups - agricultural policy - netherlands - relations between people and state

    This book describes a sociological expedition to the core of the relationship between farmers and government in the Netherlands. It focuses on the concept of mediation of agricultural policies between government and the farming target group. A starting point in this expedition is the rejection of the idea of policy-formation as a rational-synoptical chronology, in which policy is the result of a well-defined rational choice by politicians and administrators from different scenario's. Instead, policy formation in this context is understood as an incremental process: policies as a result of interaction between context induced actors. However, instead of being coincidental the interactions show up patterns of regularity that formed the motivation for this study.

    Policy mediation is defined as:

    the interrelated moments of preparation, formation, implementation and evaluation of policies,which by means of interactive processes, in which various actors (public servants, politicians, citizens, farmers, etc.) participate with their groups and projects (strategically),are geared to one another in such a manner, thatexactly therefore a legitimacy is obtained which otherwise would definitely be absent.

    The target group of agricultural policies is a so-called difuse one. That is, in need of intermediary structures able to mediate policies. The Dutch Agricultural Board (Landbouwschap) played this intermediary structure role between 1954 en 1996, when it promptly disappeared.

    In the meantime, several farmers' cooperative initiatives in one way or another have assumed the role of intermediary organizations. Central government tended to standardize their attitude towards these structures, in order to manage the policy mediation fluently. The objective of this investigation, however, is to analize and maintain the diversity of intermediary organizations. The reason is the assumption that succesful policy mediation depends on the taking account of the specifity of each structure.

    The central questions therefore are:

    in which different arrangements has the mediation of agricultural policies taken place so far,by which means could be obtained more success in terms of dynamic and legitimated policy mediation.

    Chapter 2 provides a theoretical approach of the relation between farmer and government, defining it as a particularisation of the relation between actor and structure. Instead of adhering to dualistic theories, which focus upon the complete determination of the individual by its surrounding structure (determinism) or upon the complete absence of such a determination (voluntarism), this study prefers duality as a key concept. Duality focuses upon the co-existence of contraint and enableness of the individual versus itssurrounding structure. Individuals actively make and remake social structure.

    The relation between citizen and government is subject of a process of legitimation. Public administration and policies are legitimized by:

    the procedure, with given objectives (the instrumental side of legitimation);the objectives of policies (the social contract side); andthe interchange of both.

    The chapter ends up presenting a social scientific tool to capture this legitimation process: policy-mediation.

    In chapter 3 policy mediation is surveyed in the Dutch socio-cultural heritage. In the Netherlands a strong tradition of subsidiarity and functional decentralization was founded in past centuries. The social charter of neo-corporatism is known because of its emphasis on consensus, compromise and consultation.

    Growing claims, policy overload, role distortions between public and private parties and he public opinion have shocked the traditional charter and caused a legitimation problem. Different answers are possible, varying from enforcening the state to enforcening the consensus model. In this report, there is a strong case for investing more in interdependency and participative democracy. The Dutch case shows different examples: coproduction of local policies, convenants between public governement and private parties, the socalled Green Polder Model. Although there is room for doubt because of (a) gaps between frontiers ans crowds, (b) interaction used only for self-interest. That is the risks of pseudo-participation. Therefore, field investigations are urgently needed.

    In chapter 4 an overview is given of the legitimation of agricultural policies in the Netherlands since the 19th century. The co-production tradition of farmers' organizations and central government, founded on a consensus about (a) the type of agricultural development to be nagestreefd, and (b) the need of consultation and compromise, ended up in a policy-community or - more precisely - iron triangle between farmers-leaders, ministry of agriculture and national politicians. From the late 60's, tensions grew between these parties and the iron triangle eroded. A vacuum in policy mediation became clear. Farmers reacted by protest, adaptation, individual initiatives and creating new collectivities, that became seeds of new arrangements. The following chapters describe the investigation of these new arrangements.

    Chapter 5 is a methodological intermezzo. It motivates why the sociological expedition is founded in daily reality, by describing caracteristics of factual initiatives as many and as detailed as necessary to get a sharp distinction between policy arrangements.

    In chapter 6 and 7 an inventory is made of the variation of possible arrangements, making use of 14 real collectivities in the Dutch countryside between 1980 and 1997. By adopting a cluster analysis 6 different arrangements are identified: product cooperative, horzelorganisation, farmers' association, policy cooperative, investigation cooperative and sindical organisation.

    Describing various cases in the Netherlands, in chapter 8 each arrangement is examined on its potential in terms of producing more dynamics in policy mediation. Chapter 9 also examines this potential, but now by evaluating an official policy experiment with 8 socalled environmental cooperatives (milieucoöperaties) from 1995 to 1999.

    In chapter 10, the conclusions of the expedition are summarized. The experiences of farmers' collectivities up to 1997 make clear that the state and its institutions (first of all the ministry of agriculture) are rather confused when defining an attitude against the calls for self-regulation that come from below. The state seems to get paralyzed by pleas for self-regulation on one side and the necessity to maintain principles of Good Governance on the other, one of which is gelijkberechtiging. Tailor-made policy solutions may come in conflict with the tendency to govern unilaterally from a cockpit.

    By way of recommendations, several triggers are derived from the expedition process, triggers that may give impetus to a more dynamic and prosperous relation between government and farmers. First of all, the actual situation should be understood better and more systematically by all of the parties involved. Potentials for succesful policy-mediation often aren't recognized as such.

    Next, cooperative initiatives shouldn't be put in one category too soon. Regionality, local culture and specifity are important factors for succes in policy-mediation along more selfregulation. The recognition and admission of the role local initiatives can play in succesful policy-arrangements should result in more incentives instead of penalties. State institutions should provoke and belonen a more entrepreneurial attitude of farmers. Another factor that may trigger a more dynamic relationship is the maintenance of the face-to-face caracter of policy-mediation. The personal committment of the parties involved, crucial within the agricultural population with so many individual interests and responsabilities, depends on the involvement of face-to-face contacts. This means more emphasis should be laid on local government instead of national.

    De academie van het ongewone leven : Columns over universiteit en gezin
    Hoog, K. de - \ 2000
    Wageningen : Stichting Cereales - ISBN 9789080572423 - 119
    gezinsleven - universiteiten - relaties - onderwijs - family life - universities - relationships - education
    Bosbouw en plattelandsontwikkeling in Europa
    Elands, B. ; Wiersum, F. - \ 1999
    Nederlands Bosbouwtijdschrift 71 (1999)5. - ISSN 0028-2057 - p. 204 - 207.
    bosbouw - bossen - bosbouwontwikkeling - ontwikkeling - bebossing - plattelandsontwikkeling - platteland - landbouw - relaties - bosbeleid - onderzoek - europese unie - europa - forestry - forests - forestry development - development - afforestation - rural development - rural areas - agriculture - relationships - forest policy - research - european union - europe
    Typologie van plattelandsontwikkeling en plattelandsvernieuwing, de verschillende visies op de gewenste richting van plattelandsvernieuwing (agri-ruraal; utilitair; hedonistisch), en de rol die bosbouw en vergroting van het bosareaal in Europees verband hierbij kan spelen
    Is er toekomst voor het agrarisch onderwijs?
    Bor, W. van den - \ 1998
    Agrarisch Onderwijs 40 (1998). - ISSN 0925-837X - p. 12 - 16.
    agrarisch onderwijs - onderwijs - samenleving - sociaal welzijn - sociale structuur - sociale verandering - scholen - relaties - lerarenopleiding - welzijn - bijscholing - agricultural education - education - society - social welfare - social structure - social change - schools - relationships - teacher training - well-being - continuing training
    Aandacht voor onderwijsvernieuwing waarbij vragen van arbeidsmarkt en maatschappij om antwoord vragen
    Suggestions for an oystercatcher population model
    Ens, B.J. ; Meer, J. van der - \ 1997
    Wageningen : IBN-DLO (IBN research report 97/1) - 83
    dieren - populatiedichtheid - populatie-ecologie - mortaliteit - populatiegroei - relaties - mens - wiskundige modellen - onderzoek - computersimulatie - simulatie - simulatiemodellen - waadvogels - animals - population density - population ecology - mortality - population growth - relationships - man - mathematical models - research - computer simulation - simulation - simulation models - waders
    Ketens en plattelandsontwikkeling; markt-, keten- en netwerkkennis toegepast op het landelijk gebied: een programmeringsstudie
    Hillebrand, J.H.A. ; Borgstein, M.H. ; Graaff, R.P.M. de; Scherpenzeel (Rijksuniv.), J.F. ; Sijtsma (RU.), F.J. ; Strijker (RU.), D. - \ 1997
    Den Haag : Nationale Raad voor Landbouwkundig Onderzoek - ISBN 9789050590426 - 96
    plattelandsplanning - plattelandsontwikkeling - sociale economie - marketing - bedrijfsvoering - markten - marktconcurrentie - aanbodsevenwicht - intermenselijke relaties - relaties - consumenten - onderzoek - vraag - consumentengedrag - landbouw - productiestructuur - agrarische structuur - overheidsbeleid - economie - wetgeving - Nederland - economische planning - rural planning - rural development - socioeconomics - marketing - management - markets - market competition - supply balance - interpersonal relations - relationships - consumers - research - demand - consumer behaviour - agriculture - production structure - agricultural structure - government policy - economics - legislation - Netherlands - economic planning
    Grondverwerving voor natuur: het rijk van provincies? De provinciale oriëntaties op grondverwerving voor bosuitbreiding in de Randstad, natuurontwikkeling en reservaatvorming
    Kuindersma, W. ; Zweegman, G.J. - \ 1997
    Wageningen : IBN-DLO - 89
    natuurbescherming - beleid - bedrijfsvoering - natuurreservaten - herstel - overdrachten van grond - land - acquisitie - regionaal bestuur - bosbouw - hulpbronnen - relaties - bossen - milieubescherming - conservering - nederland - natuur - natuurtechniek - provincies - districten - nature conservation - policy - management - nature reserves - rehabilitation - land transfers - land - acquisition - regional government - forestry - resources - relationships - forests - environmental protection - conservation - netherlands - nature - ecological engineering - provinces - districts
    Bosuitbreiding in Nederland ligt niet op schema
    Edelenbosch, N.H. - \ 1997
    Nederlands Bosbouwtijdschrift 69 (1997)5. - ISSN 0028-2057 - p. 231 - 236.
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - landbouwstatistieken - oppervlakte (areaal) - nederland - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - agricultural statistics - acreage - netherlands
    Gemeenten kunnen meer bos aanleggen; evaluatie van bosuitbreiding door gemeenten
    Doppenberg, M.H. ; Landman, A.V. ; Edelenbosch, N.H. ; Hekhuis, H.J. - \ 1997
    Groen : vakblad voor groen in stad en landschap 53 (1997)11. - ISSN 0166-3534 - p. 40 - 45.
    bosbouw - landgebruik - pachtstelsel - bebossing - hulpbronnen - relaties - economie - gebruikswaarde - economische impact - forestry - land use - tenure systems - afforestation - resources - relationships - economics - use value - economic impact
    Mushrooms: more than just taste (in Dutch)
    Leguijt, C. ; Valk, H.C.P.M. van der; Sanders, M.G. ; Termeer, A.G.W. ; Vuurst de Vries, R.G. van der; Yüksel, D. ; Wichers, H.J. - \ 1997
    De Champignoncultuur 41 (1997)8. - ISSN 0009-1316 - p. 277 - 285.
    agaricus - chemische structuur - relaties - organoleptische kenmerken - markten - marketing - marktconcurrentie - aanbodsevenwicht - tuinbouwgewassen - biologische eigenschappen - agaricus - chemical structure - relationships - organoleptic traits - markets - marketing - market competition - supply balance - horticultural crops - biological properties
    Het versterken van de positie van Nederlandse champignonbedrijven is nodig om de afzetmogelijkheden te verruimen. Drie deelprojecten zijn genoemd die in het kader van de afzet worden uitgevoerd. Het eerste dat gaat over de karakterisering van smaak, geur en textuur van verse champignons is in dit artikel uiteengezet
    Economics of timber plantations on CO2-emissions in the Netherlands.
    Slangen, L.H.G. ; Kooten, G.C. van; Rie, J.P.P.F. van - \ 1997
    Tijdschrift voor sociaalwetenschappelijk onderzoek van de landbouw 12 (1997)4. - ISSN 0921-481X - p. 318 - 333.
    broeikaseffect - opwarming van de aarde - bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - overheidsbeleid - landbouwbeleid - agrarisch recht - nederland - greenhouse effect - global warming - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - government policy - agricultural policy - agricultural law - netherlands
    Met een kosten-batenanalyse wordt nagegaan in welke mate bebossing van landbouwgronden in Nederland een kostenefficiente methode kan zijn om de CO2-concentratie te verlagen
    Essays in economics of renewable resources
    Bulte, E.H. - \ 1997
    Agricultural University. Promotor(en): H. Folmer; W.J.M. Heijman. - S.l. : Bulte - ISBN 9789054856993 - 283
    duurzaamheid (sustainability) - natuurlijke hulpbronnen - hulpbronnengebruik - bescherming - herstel - milieu - kwaliteit - controle - verontreinigingsbeheersing - milieubeheer - bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - vis vangen - visserij - economie - tropen - nationaal vermogen - sustainability - natural resources - resource utilization - protection - rehabilitation - environment - quality - control - pollution control - environmental management - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - fishing - fisheries - economics - tropics - national wealth

    In dit proefschrift neem ik een aantal onderwerpen die betrekking hebben op de economische theorie van beheer van natuurlijke hulpbronnen onder de loep. Voorbeelden van natuurlijke hulpbronnen zijn visvoorraden, bossen en olie. Het onderzoeksveld is breed en biedt keuze uit een scala aan onderwerpen, ieder met zijn eigen problemen, eigenaardigheden en interessante aspecten. Aangezien de afzonderlijke hoofdstukken van dit proefschrift afgesloten worden met een concluderende en samenvattende sectie, zal ik deze samenvatting kort houden.

    De hoofdstukken 1 en 2 betreffen een inleidend literatuuronderzoek. In hoofdstuk 1 wordt het onderzoeksveld afgebakend en worden enkele basisbegrippen besproken. Twee centrale thema's zijn "duurzaamheid" en "efficientie". Duurzaamheid heeft betrekking op gelijke toegang tot natuurlijke hulpbronnen door verschillende generaties. Efficiëntie betekent het (intertemporeel) maximaliseren van een doelfunctie. Het maximaliseren van "de winst of "het nut voor de samenleving" zijn veel gebruikte voorbeelden van dergelijke functies. Na de Earth summit in Rio de Janeiro in 1992 zou "duurzaamheid" wellicht het belangrijkste thema van de twee dienen te zijn, maar er bestaat in de literatuur veel verschil van inzicht over de exacte interpretatie van dit begrip. De interpretatie is subjectief en onder andere afhankelijk van de inschatting van de toekomstige substitutie-mogelijkheden tussen de verschillende productiefactoren (bijvoorbeeld tussen natuurlijk en fysiek kapitaal), en van de mogelijkheden die in de toekomst door technologische vooruitgang geboden zullen worden.

    De interpretatie van efficiëntie is helder, en de mainstream van de neoklassieke economen is traditioneel gericht op dit thema. (Van meer recente aard zijn modellen waarin de beide thema's gecombineerd worden.) De meeste hoofdstukken in dit proefschrift gaan in de eerste plaats over het efficiënt gebruik van (vernieuwbare) natuurlijke hulpbronnen.

    Het exploiteren van een natuurlijke hulpbron heeft invloed op de mogelijkheden voor toekomstig gebruik van deze voorraad. In geval van mijnbouw, bijvoorbeeld, gaat de huidige extractie van ertsen ten koste van grondstofwinning in de toekomst. Dit impliceert dat bij het delven van een eenheid erts, in aanvulling op de pure extractiekosten, rekening moet worden gehouden met de zogenaamde opportunity costs . In dit verband wordt met opportunity costs bedoeld de mogelijke baten die de eenheid erts in de toe komst had kunnen opleveren. Deze "extra" kosten verlagen de optimale hoeveelheid die geëxploiteerd dient te worden. Een belangrijke regel voor efficiënt gebruik van een niet-vernieuwbare hulpbron, zoals olie of steenkool, is dat onder bepaalde voorwaarden de groeivoet van de zogenaamde rent van de hulpbron (gedefinieerd als het verschil tussen de prijs en de marginale exploitatiekosten) gelijk moet zijn aan de interestvoet. Als deze regel opgaat zijn eigenaren van een hulpbron indifferent tussen huidige en toekomstige extractie: het rendement van het aanhouden van een voorraad van een bepaal
    de hulpbron is even hoog als het rendement van exploiteren en het verdiende geld vervolgens elders investeren of op de bank zetten. Dit is de bekende Hotelling regel.

    Voor efficiënt gebruik van hulpbronnen die zichzelf binnen een redelijke termijn kunnen vernieuwen, zoals een voorraad vis of een bos, moet de Hotelling regel aangepast worden. In de economie van dit soort hulpbronnen worden economische principes gecombineerd met biologische groeimodellen. Met behulp van bosbouwmodellen kan dan bijvoorbeeld de optimale omlooptijd van een gelijkjarig bos berekend worden. Met behulp van visserijmodellen wordt de optimale visstand in een bepaald gebied berekend. Het afzien van oogsten, bijvoorbeeld door een hoeveelheid bomen nog een jaar te laten groeien of door de jaarlijkse vangst van een bepaalde vissoort te verlagen, kan geïnterpreteerd worden als "investeren" in de hulpbron. Omgekeerd geldt dat oogsten gelijk staat aan desinvesteren. In hoofdstuk 2 van dit proefschrift wordt door middel van een literatuurstudie ingegaan op deze materie en op verwante zaken als eigendomsrechten (immers, wie wil investeren in een hulpbron als niet duidelijk is of de toekomstige baten toevallen aan hemzelf?) en de rol van overheidsbeleid.

    Hoofdstuk 3 en 4 zijn gewijd aan tropische ontbossing. Het directe verband tussen de commerciële kap van tropisch hardhout en ontbossing is uiterst zwak. Een veel belangrijkere factor is het "omzetten" van bossen in landbouwgrond (ongeveer 80% van alle ontbossing wordt veroorzaakt omdat ruimte voor landbouw, inclusief veehouderij, gemaakt moet worden). Zoals veel bosbouwers en milieubeschermers benadrukken bestaat er echter wel een sterk indirect verband tussen commerciële, selectieve houtkap en oprukkende landbouw. De bosbouwsector zorg namelijk voor het aanleggen van een infrastructuur in gebieden waar (selectief) gekapt is. Dit maakt het bedrijven van landbouw in deze gebieden aantrekkelijker.

    Een veel gehoorde beleidsaanbeveling is dat boeren uit de bossen geweerd moeten worden, bij voorkeur door een algemeen ontwikkelingsbeleid gericht op het tegengaan van te snelle bevolkingsgroei, het bevorderen van alfabetisering en het hervormen van de landbouwsector. Ongetwijfeld wordt hiervoor met de beste bedoelingen gepleit. Dit proefschrift toont echter aan dat dit beleid niet altijd bevorderlijk is voor natuurbehoud.

    In hoofdstuk 3 wordt de relatie tussen de (dreiging van) oprukkende boeren en het kaptempo van bosbouwers onderzocht. Omdat, zoals vermeld, conversie van bossen in landbouwgrond met name voorkomt in selectief gekapt bos, kunnen bosbouwers met kapconcessies voor meerdere jaren de schade door oprukkende landbouwers beïnvloeden door hun kapbeslissingen ("in welk tempo zet ik mijn ongestoorde, primaire bos om in makkelijk toegankelijk, secundair bos?") te veranderen. Het verminderen van schade zal overwogen worden indien het bosbouwers is toegestaan na verloop van tijd terug te keren naar het opengelegde gebied voor aanvullende kap. Met een model waar schade aan het bosbestand van een houtbedrijf positief gerelateerd is aan de omvang van het secundaire bos laten we zien dat de dreiging van oprukkende boeren twee effecten heeft. Aan de ene kant zullen bosbouwers de kap in toegankelijke bossen intensiveren om de brandende boeren vóór te zijn. Een andere reactie is het vertragen van de omzetting van ongestoorde (en ontoegankelijke) primaire bossen in secundaire bossen. We concluderen dat de dreiging van landbouwers leidt tot minder secundair en meer primair bos. Afhankelijk van de maatschappelijke waardering voor deze verschillende bossystemen kan dit uit oogpunt van natuurbehoud een verbetering of een verslechtering inhouden.

    Het huidige tempo van ontbossing is volgens velen te hoog. Een mogelijke verklaring is dat kapbedrijven een te hoge rentevoet hanteren bij het beslissen over de spreiding van kapactiviteiten over de tijd. Immers, veelal wordt verondersteld dat hogere discontovoeten (implicerend dat relatief meer belang wordt gehecht aan huidige consumptie dan aan toekomstige consumptie) ondubbelzinnig negatief uitpakken voor natuurbescherming. Een tweede doelstelling van hoofdstuk 3 is te onderzoeken of dit correct is in de context van een model waarin onderscheid gemaakt wordt tussen primaire en secundaire bossen en waarin een winstmaximaliserend bedrijf geconfronteerd wordt met een overheid die bepaalde eisen stelt. We laten zien dat hoge rentevoeten niet noodzakelijkerwijs versnelde kap uitlokken. Het selectief kappen van primair bos betekent namelijk automatisch dat secundair bos gecreëerd wordt. Bij optimaal bosbeheer wordt de winst door kap in beide typen bos in de afweging betrokken. We laten zien dat hoge discontovoeten de baten van het omzetten van primair bos in secundair bos verlagen. Daarmee wordt het tempo vertraagd waarin deze primaire bossen dienen te worden gekapt om de winst te maximaliseren.

    In hoofdstuk 4 onderzoeken we of het verschaffen van ontwikkelingsgeld aan ontwikkelingslanden een efficiënt instrument is om tropische ontbossing af te remmen. Op basis van een model waar de overheid van een Derde Wereldland de baten van bosbeheer maximaliseert, in dit geval opbrengsten uit verkoopbaar hout en niet-gebruikswaarden gekoppeld aan bosbescherming, is in het verleden geconcludeerd dat ontwikkelingshulp leidt tot extra bosbescherming. De redenering luidt als volgt: extra geld door middel van internationale transfers leidt tot meer consumptie in het Derde Wereldland, zodat de marginale baten van consumptie zullen dalen. Om het evenwicht te herstellen moeten de marginale baten van bosbescherming ook dalen, hetgeen alleen bereikt kan worden door het bosareaal uit te breiden. We hebben dit model uitgebreid en realistischer gemaakt door een risico-mijdende overheid en onzekerheid met betrekking tot toekomstige houtprijzen te veronderstellen. Uiteraard leidt deze uitbreiding normaliter tot afremmen van de kapinspanning. In aanvulling op dit effect hebben internationale donaties in het uitgebreide model een tweede effect: de overheid wordt door het extra geld minder risico-mijdend en laat zich in mindere mate door de onzekere prijzen afremmen om bos te kappen. De conclusie is dat de effectiviteit van internationale transfers als instrument om bij te dragen tot bosbescherming in het verleden is overschat.

    In hoofdstuk 5 en 6 behandelen we enkele economische achtergronden van het beschermen van bepaalde diersoorten. In hoofdstuk 5 staat het verbod op de handel in ivoor centraal. Met de bedoeling om olifanten te beschermen is hiertoe, na enkele decennia van grootschalige olifantenslacht, besloten aan het einde van de jaren '80. Tot op heden heeft dit beleid bijgedragen aan herstel van olifantenpopulaties. Met een eenvoudig economisch model hebben we onderzocht of een handelsverbod altijd dit effect zal blijven hebben. Dit is waarschijnlijk niet het geval. Voor een overheid levert het beheren van een populatie levende olifanten verschillende baten op: het trekt toeristen aan en, na eventuele opheffing van het verbod, zijn olifanten een bron van ivoor en andere nuttige producten. Aan de andere kant leveren olifanten schade op aan landbouwgewassen en mogelijkerwijs ook aan natuurparken. Zolang het handelsverbod gehandhaafd blijft zal een overheid proberen de baten van de bescherming van een extra olifant (in dit geval dus inkomsten uit toerisme) gelijk te stellen aan de kosten die deze olifant met zich meebrengt. Dit wordt bereikt door regelmatig olifantenpopulaties uit te dunnen, ook al mag het aldus verkregen ivoor niet verkocht worden. Dergelijke operaties zijn in enkele landen al aan de gang. Indien het handelsverbod wordt opgeheven zal de overheid olifanten ook beschouwen als een vernieuwbare bron van ivoor. Het bejagen van olifanten voor ivoor levert dan directe baten op en het laten leven van een olifant wordt een soort van investering. Met behulp van data voor Afrika in het algemeen en Kenia in het bijzonder laten we zien dat de optimale populatie olifanten zoals die met een handelsverbod door een overheid wordt nagestreefd niet noodzakelijkerwijs groter is dan de optimale populatie met handel in ivoor. Een belangrijke factor die de optimale hoeveelheid olifanten in de situatie met handel bepaald is de hoogte van de discontovoet die de overheid gebruikt. Een hoge discontovoet leidt tot lage olifantenpopulaties wanneer handel in ivoor is toegestaan, en omgekeerd. De discontovoet waarbij de hoeveelheid olifanten met handel in ivoor de optimale populatie met een handelsverbod overtreft is in de nabijheid van de "sociale discontovoet". Als de discontovoet zoals gehanteerd door Afrikaanse overheden lager wordt dan deze break even discount rate, dan zijn olifanten gebaat bij handel in ivoor. Aangezien de discontovoet waarschijnlijk niet constant is (veelal wordt verondersteld dat de discontovoet een afnemende functie van het inkomen is), concluderen we dat olifantenbeschermers in de toekomst wellicht zullen moeten pleiten voor opheffing van het handelsverbod. In het model hebben we geen rekening gehouden met stroperij. Dit beschouwen we een van de noodzakelijke uitbreidingen voor de toekomst.

    In hoofdstuk 6 bekijken we de economische achtergrond van het verbod op de commerciële walvisvaart. We berekenen de optimale hoeveelheid dwergvinvissen in het Noordoostelijk deel van de Atlantische oceaan met behulp van een model waarin we rekening houden met de niet-gebruikswaarden van levende walvissen (de populariteit van organisaties als Greenpeace geeft aan dat veel mensen "nut" ontlenen aan levende walvissen). In tegenstelling tot ander onderzoek concluderen we dat de huidige populatie dwergvinvissen te laag is. Bovendien blijkt dat het optimaal is om volledig van walvisvangst af te zien tot de populatie gegroeid is tot de optimale omvang. Het moratorium is dus economisch te verdedigen. In het hoofdstuk demonstreren we tot slot dat een simpel statisch model, dat door sommige onderzoekers wordt gebruikt om dit soort problematiek te benaderen, ongeschikt is. Het model leidt tot beleidsaanbevelingen die diametraal tegenover de beleidsimplicaties van een dynamische specificatie staan.

    De hoofdstukken 7, 8 en 9 betreffen visserijeconomie. Zoals besproken in hoofdstuk 2 heeft exploitatie van de zee gedurende een lange tijd plaatsgevonden onder condities van open access. Dit betekent dat het niet mogelijk was om geïnteresseerde vissers te weren van bepaalde visgronden. Omdat niemand geweerd kon worden, voelde niemand zich verantwoordelijk voor een duurzaam beheer. Iedereen zal proberen op zo kort mogelijk termijn zo veel mogelijk geld te verdienen door vis te vangen voordat een andere visser daar aan toe komt. Onder open access verdwijnt de rent volledig: er wordt zoveel gevist dat de prijs uiteindelijk gelijk is aan de marginale vangstkosten. Aan het eind van de jaren '70 is aan deze toestand een einde gekomen door het instellen van exclusieve zones waarbinnen overheden het recht krijgen om buitenstaanders te weren en eigen beleid te voeren. We hebben in hoofdstuk 7 onderzocht of de overgang van open access naar een situatie waar overheidsbeleid gevoerd kan worden heeft geleid tot een beter beheer van visbestanden. Op basis van de economische theorie kan voorspeld worden dat overheden (net als bedrijven met gegarandeerde eigendomsrechten) rekening houden met levende vissen als investering. Dit betekent dat de rent van de hulpbron positief moet worden. Empirisch onderzoek met behulp van Duitse data wijst uit dat de rent inderdaad positief geworden is na instellen van Europees visserijbeleid.

    De conclusie uit hoofdstuk 7 is zeker niet dat het huidige beleid optimaal is. Er werd slechts geconcludeerd dat vergeleken met vroeger de hulpbron nu efficiënter geëxploiteerd wordt. Ander onderzoek heeft aangetoond dat het huidige beleid verre van optimaal is. Een verklaring voor suboptimaal visserijbeheer (die verrassend vaak over het hoofd wordt gezien) is dat de standaard-veronderstelling dat overheden proberen "de welvaart voor de samenleving te maximaliseren", niet opgaat. De overheid wordt beïnvloedt door belangengroepen met bepaalde doelstellingen, die kunnen afwijken van wat sociaal wenselijk is. In hoofdstuk 8 laten we zien dat een belangengroepen- benadering, waarin we vissers, arbeiders en consumenten onderscheiden, leidt tot beheer dat afwijkt van hetgeen standaardmodellen voorschrijven. De observatie dat er onvoldoende vis rondzwemt in de Noordzee hoeft niet noodzakelijkerwijs te impliceren dat de overheid haar doelstellingen niet haalt door het verkeerd inzetten van bepaalde instrumenten. Het kan even goed wijzen op afwijkende doelstellingen als gevolg van lobbyende belangengroepen.

    In hoofdstuk 8 wordt expliciet rekening gehouden met de "macht" van de visserijsector. Het is niet realistisch om te veronderstellen dat een overheid simpelweg een bepaald beleid kan voeren dat rechtstreeks tegen de belangen van bepaalde groepen ingaat. In hoofdstuk 9 laten we zien hoe, in het geval van de visserij, een overheid beperkende maatregelen (zoals het verkleinen van quota) kan doorvoeren zonder de belangen van de vissers al te zeer te schaden. Het instellen van een termijnmarkt voor verhandelbare visquota neemt het prijsrisico dat vissers lopen voor deze quota weg. Dit betekent dat een risico-mijdende visser beter af is dan voorheen. Dit biedt het perspectief om op hetzelfde moment het quotum te verlagen, zodat per saldo de visser niet beter of slechter af is. Financiële instrumenten kunnen dus (in theorie) leiden tot bescherming van natuurlijke hulpbronnen.

    Het proefschrift bevat tot slot twee hoofdstukken over bosbouw waarin onzekerheid een belangrijke rol speelt. In hoofdstuk 10 laten we zien hoe een bepaald soort onzekerheid met betrekking tot de (veelal strijdige) voorkeuren van beleidmakers (bijvoorbeeld: "werkgelegenheid is heel belangrijk, maar de hoeveelheid natuur mag niet veel kleiner worden") geïncorporeerd kan worden in een landgebruiksmodel. Daarnaast behandelen we onzekerheid die samenhangt met gebrekkige kennis omtrent technische coëfficiënten in bosbouwmodellen. We gebruiken fuzzy set theorie, gebaseerd op membership functions, om onzekerheid te modelleren. Een cruciaal aspect van fuzzy logic is dat elementen gedeeltelijk tot een bepaalde set kunnen behoren. We vinden dat de resulterende landallocatie te verkiezen valt boven de uitkomsten van een rechttoe-recht-aan model.

    In hoofdstuk 11 behandelen we een heel ander soort onzekerheid. Zoals boven vermeld fluctueren houtprijzen in de praktijk. In tegenstelling tot .fuzzy set theorie (waarbij niet het plaatsvinden van een gebeurtenis onzeker is, maar de gebeurtenis zelf) is de kansverdeling van de stochastische prijs bekend. In de literatuur is een zoekmodel met reserveringsprijzen ontwikkeld om de baten van een strategisch, flexibel kapbeleid (kappen wanneer de prijs hoger is dan de reserveringsprijs, afzien van kappen indien de prijs lager is) te kunnen vergelijken met de opbrengsten van het meer rigide Faustmann model (zie ook hoofdstuk 2). Uit studies blijkt dat de winsten van Boseigenaren met ongeveer 30% stijgen wanneer een reserveringsprijs-benadering gekozen wordt. In hoofdstuk 11 hebben we dit model uitgebreid door in aanvulling op strategische eindkap ook strategisch uitdunnen in ogenschouw te nemen. We vinden dat de reserveringsprijs voor uitdunnen altijd lager is dan de reserveringsprijs voor kappen en dat een strategisch kapbeleid ten aanzien van uitdunnen de winst van een boseigenaar substantieel verhoogd. De extra baten van flexibel uitdunnen zijn, in overeenstemming met de verwachtingen, minder groot dan de extra baten van het volgen van een strategisch eindkapbeleid.

    The structure of particle gels as studied with confocal microscopy and computer simulations
    Bos, M.T.A. - \ 1997
    Agricultural University. Promotor(en): B.H. Bijsterbosch; P. Walstra; J.H.J. van Opheusden. - S.l. : Bos - 108
    chemische structuur - optische eigenschappen - relaties - chemical structure - optical properties - relationships

    This thesis contains the results of a PhD-study on the structure of particle gels. Part of it is directed at a quantification of this structure from measured data, part of it at modelling the aggregation processes that lead to particle gels. Chapter 1 of this thesis is a general introduction describing the aim of this study.

    Chapter 2 introduces aggregation and gelation of particles. As to the modelling of aggregation we conclude that there are two types of approach: one based on thermodynamics and one based on fractal aggregation (Diffusion Limited Cluster Aggregation or DLCA). The former is appropriate for reversible aggregation, the latter for irreversible aggregation. For all types of colloidal aggregation which are in between these two extremes, an understanding based on both approaches is needed. We use fractal aggregation models as a starting point, but recognise the importance of cluster reorganisation, which will cause gels with structures different than predicted in DLCA. As to quantification of fractal structure, a lower cutoff length scale r 0 is suggested as a valuable addition to the fractal dimensionality d f .

    Chapter 3 describes Confocal Scanning Laser Microscopy (CSLM) as a tool to study the structure of various particle gels. An in-depth optical treatment of imaging in CSLM is presented, along with a new way of image enhancement using calculated three dimensional point spread functions. It is concluded that image enhancement is essential in order to get useful results from an analysis of CSLM micrographs.

    Chapter 4 shows the results on the fractal structure of particle gels derived from CSLM micrographs of colloidal model systems. It explains thoroughly the details of the image analysis procedure and identifies possible problems, most notably background intensities. From the results it appears that all fractal dimensionalities are about equal, with values larger than the DLCA limit. The values of r 0 show that there are significant differences between gel structures despite the similarities in d f . These differences are difficult to connect with properties of the colloidal model systems. A hypothesis about a ' pre- aggregation stage' is formulated which might serve as a starting point for further research.

    In Chapters 5 and 6 Brownian Dynamics simulations are used as a tool for forming a better connection between aggregation and gel structure. For aggregating Lennard-Jones systems (Chapter 5) we find percolating networks at high volume fractions; these appear to be formed by reorganisation of large aggregates, during which branched strands are formed with voids in between. The gel structure is influenced by both cluster growth and cluster reorganisation; fractal analysis gives non-universal, i.e. time dependent results. For the Lennard-Jones potential, the aggregation is dominated by cluster reorganisation. Aggregating particles with a shorter potential range (Chapter 6) also show time dependent fractal results, but by decreasing the potential range the balance between cluster growth and cluster reorganisation becomes more subtle. Reorganisation of clusters occurs at a lower rate when the potential range is decreased. A large potential well depth εboth promotes reorganisation and inhibits it because of irreversible clustering. A thermodynamical analysis shows that this effect will become more pronounced for shorter ranged potentials.

    Chapter 7 generalises the conclusions of all previous chapters and gives suggestions for further research. All results in this thesis have used available computing resources up to the maximum. Given the ever growing computing power, significantly more sophisticated techniques for simulation or image analysis will become available within years.
    The work described in this thesis has led to the following publications:

    J.H.J. van Opheusden, M.T.A. Bos, 'Induced flocculation of casein micelles - a Brownian Dynamics
    simulation on the Parsytec Gcel MPP', Future. Gener. Comp. Sy. 11123-133, 1995

    BE. Bijsterbosch, M.T.A. Bos, E. Dickinson, J.H.J. van Opheusden, P. Walstra, "Brownian dynamics simulation of particle gel formation: From argon to yoghurt", Faraday Discuss. 10151-64, 1995

    M.T.A. Bos, J.H.J van Opheusden, "Brownian dynamics simulation of gelation and aging in interacting colloidal systems", Phys Rev E 53 5044-5050, 1996

    Plant domestication and evolution : a monovular twin or not?
    Raamsdonk, L.W.D. van - \ 1996
    Wageningen : CPRO-DLO - 101
    oorsprong - distributie - vestiging - wilde planten - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - fylogenie - fylogenetica - relaties - gewassen - acclimatisatie - domesticatie - plantkunde - nieuwe cultuurgewassen - economische botanie - origin - distribution - establishment - wild plants - genetics - genetic variation - evolution - speciation - immunogenetics - phylogeny - phylogenetics - relationships - crops - acclimatization - domestication - botany - new crops - economic botany
    Runoff and sediment transport in the arid regions of Argentina and India - a case study in comparative hydrology
    Sharma, K.D. ; Menenti, M. ; Huygen, J. ; Fernandez, P.C. ; Vich, A. - \ 1996
    Annals of Arid Zone 35 (1996)1. - ISSN 0570-1791 - p. 17 - 28.
    argentinië - woestijnen - economische impact - economie - india - regen - relaties - oppervlakkige afvoer - gebruikswaarde - aride klimaatzones - argentina - deserts - economic impact - economics - india - rain - relationships - runoff - use value - arid zones
    The arid zones of Argentina and India have been compared. In both regions run-off is often generated by the Hortonian infiltration surplus overland flow, and run-off response to precipitation input tends to be rapid. The sediment transport is governedby the transport capacity of run-off rather than by the availability of erodible material. The magnitude of hydrological processes is different in response to the different rainfall regimes.
    Establishing temporally and spatially variable soil hydraulic data for use in a runoff simulation in a loess region of the Netherlands
    Stolte, J. ; Ritsema, C.J. ; Veerman, G.J. ; Hamminga, W. - \ 1996
    Hydrological Processes 10 (1996)8. - ISSN 0885-6087 - p. 1027 - 1034.
    hydraulisch geleidingsvermogen - infiltratie - modellen - regen - relaties - onderzoek - oppervlakkige afvoer - kwel - geostatistiek - limburg - hydraulic conductivity - infiltration - models - rain - relationships - research - runoff - seepage - geostatistics - limburg
    Soil hydraulic functions for run-off simulation were collected in catchment areas in a loess region. Each soil horizon was sampled and water retention and hydraulic conductivity characteristics were determined. Run-off generation during standard rain events was quantified by simulation. Based on the simulation outcome, soil horizons were merged. The soil physical composition was mapped with these soil physical building blocks. The maps can be used as input for soil and water erosion models on catchment scale. Comparison of potential run-off figures with measured data showed that the soil physical schematization was appropriate.
    LISEM: a single-event physically based hydrological and soil erosion model for drainage basins; I: theory, input and output
    Roo, A.P.J. de; Wesseling, C.G. ; Ritsema, C.J. - \ 1996
    Hydrological Processes 10 (1996)8. - ISSN 0885-6087 - p. 1107 - 1117.
    erosie - geografische informatiesystemen - modellen - regen - relaties - onderzoek - oppervlakkige afvoer - bodem - erosion - geographical information systems - models - rain - relationships - research - runoff - soil
    The Limburg Soil Erosion Model (LISEM) is a physically based model incorporated in a raster geographical information system. This incorporation facilitates easy application in larger catchments, improves the user-friendliness by avoiding conversion routines and allows the use of remotely sensed data. Processes incorporated in this model are rainfall, interception, surface storage in microdepressions, infiltration and vertical movement of water in the soil, overland flow, channel flow, detachment by rainfall and through-fall, detachment by overland flow and transport capacity of the flow. Special attention has been paid to the influence of tractor wheeling, small roads and surface sealing.
    Inzet van een tendersysteem bij de SBL-regeling
    Ham, A. van den; Kolkman, G. - \ 1996
    Wageningen : IBN-DLO - 45
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - subsidies - premies - regering - bedrijfsvoering - bestedingen - dienstensector - overheidsbestedingen - nederland - voorzieningen - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - subsidies - grants - government - management - expenditure - services - public expenditure - netherlands - facilities
    Boerenbosbouw is zo gek nog niet; Noordelijke agrariërs stappen over op bosbouw.
    Konijnendijk, C.C. ; Laar, J.N. van - \ 1996
    Nederlands Bosbouwtijdschrift 68 (1996)1. - ISSN 0028-2057 - p. 7 - 11.
    bosbouw - weiden - bossen - landbouwgrond - relaties - bebossing - veenkolonien - forestry - pastures - forests - agricultural land - relationships - afforestation - veenkolonien
    Particuliere bosbouw in Nederland: een nieuwe toekomst?
    Wiersum, K.F. - \ 1996
    Nederlands Bosbouwtijdschrift 68 (1996)1. - ISSN 0028-2057 - p. 12 - 17.
    bosbouw - bosbezit - particuliere bosbouw - bossen - particulier eigendom - weiden - landbouwgrond - relaties - ontbossing - bebossing - inkomen - rendement - bestedingen - winsten - kosten - bosbedrijfsvoering - investering - financiën - nederland - forestry - forest ownership - private forestry - forests - private ownership - pastures - agricultural land - relationships - deforestation - afforestation - income - returns - expenditure - profits - costs - forest management - investment - finance - netherlands
    Wat ga jij nu doen? Leren voor oordeelsvorming en besluitvaardigheid.
    Haarlem, R. van - \ 1996
    Agrarisch Onderwijs 38 (1996)18. - ISSN 0925-837X - p. 8 - 10.
    besluitvorming - scholen - samenwerking - relaties - organisaties - genetische modificatie - recombinant dna - ethiek - onderwijs - mentale vaardigheid - duurzaamheid (sustainability) - projecten - agrarisch onderwijs - hoger onderwijs - beroepsopleiding - colleges - universiteiten - onderwijsmethoden - moraal - utilisme - probleemgestuurd onderwijs - decision making - schools - cooperation - relationships - organizations - genetic engineering - recombinant dna - ethics - education - mental ability - sustainability - projects - agricultural education - higher education - vocational training - colleges - universities - teaching methods - moral - utilitarianism - problem-based learning
    Heidegger en de wereld van het dier.
    Blans, G.H.T. ; Lijmbach, S.E.E.M. - \ 1996
    Assen : Van Gorcum - 78
    diergedrag - dieren - antropologie - mens - filosofie - psychologie - relaties - metafysica - geest - filosofische stelsels - animal behaviour - animals - anthropology - man - philosophy - psychology - relationships - metaphysics - mind - philosophical systems
    The effects of changing land use on the behavior of copper in the soil
    Koopmans, G.F. - \ 1995
    Haren (Gr.) : AB-DLO (Rapport / DLO - Instituut voor Agrobiologisch en Bodemvruchtbaarheidsonderzoek 30) - 24
    koper - bodem - bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - copper - soil - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation
    Neerslagspreiding en aanvoerreductie in het regionale afvalwatertransportstelsel van het Hoogheemraadschap West-Brabant
    Dircke, P.T.M. ; Witter, J.V. ; Stricker, J.N.M. - \ 1995
    Wageningen : Landbouwuniversiteit Wageningen (Rapport / Landbouwuniversiteit, Vakgroep Waterhuishouding 49) - 134
    afvalwater - hydrologie - modellen - regen - afvalwaterbehandeling - oppervlakkige afvoer - nederland - noord-brabant - waste water - analogues - hydrology - models - waste water treatment - relationships - water treatment - noord-brabant
    Nederlandse ervaringen met de biomassaproduktie van populier en wilg in zeer korte omlopen
    Burg, J. van den; Dik, E.J. - \ 1995
    Nederlands Bosbouwtijdschrift 67 (1995)1. - ISSN 0028-2057 - p. 23 - 27.
    bosbouw - bosplantages - intensieve houtteelt - biomassa - snelgroeiende stammen - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - nederland - forestry - forest plantations - intensive silviculture - biomass - rapidly growing strains - pastures - forests - agricultural land - relationships - deforestation - afforestation - netherlands
    Woody plants in agro-ecosystems of semi-arid regions
    Breman, H. ; Kessler, J.J. - \ 1995
    Springer Verlag (Advanced Series in Agricultural Sciences ) - ISBN 9783642792090
    bosbouw - agroforestry - ecologie - gewassen - landbouw - fenologie - acclimatisatie - gemengde teelt - tussenteelt - meervoudige teelt - tussenplanting - bedrijfssystemen - relaties - steppen - pampa's - semi-aride klimaatzones - agro-ecosystemen - forestry - agroforestry - ecology - crops - agriculture - phenology - acclimatization - mixed cropping - intercropping - multiple cropping - interplanting - farming systems - relationships - steppes - pampas - semiarid zones - agroecosystems
    A quantitative analysis of the role of woody plants in semi-arid regions, focusing on the Sahel and Sudan zones in West-Africa, is given for the assessment of their benefits in agro-sylvopastoral land-use systems with productive and sustainability objectives.
    La regeneration de l'espace sylvo-pastoral au Sahel : une etude de l'effet de mesures de conservation des eaux et des sols au Burkina Faso
    Hien, F.G. - \ 1995
    Agricultural University. Promotor(en): L. Stroosnijder. - S.l. : Hien - 223
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - silvopastorale systemen - bosweiden - erosiebestrijding - waterbescherming - bodembescherming - duurzaamheid (sustainability) - natuurlijke hulpbronnen - hulpbronnengebruik - bescherming - herstel - burkina faso - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - silvopastoral systems - woodland grasslands - erosion control - water conservation - soil conservation - sustainability - natural resources - resource utilization - protection - rehabilitation - burkina faso
    Sahelian rangelands are subject to degradation caused by physical and human factors. This report presents the results of recent research in Burkina Faso on methods for regenerating such rangelands. It begins with an overview of existing regeneration methods. Quantitative ecological field work conducted at two representative sites to understand the regeneration processes, to determine the sustainability of these processes and to understand reasons for success or failure of regeneration technology is described. Water and nutrient (N,P and K) balances as well as vegetation dynamics were studied for different soil and water conservation technologies. A major conclusion is that degraded and crusted soils can only be regenerated by modifying the water balance. Under improved infiltration, subsequent biological processes appear to be able to transform degraded soils into productive soils. However, an improved availability of water often triggers an immediate shortage of nitrogen. Deep infiltration of water stimulates the growth of trees and shrubs which have a stabilizing effect on the overall regeneration process of Sahelian rangelands.
    Interspecific competition, predation, and the coexistence of three closely related neotropical armoured catfishes (Siluriformes - Callichthyidae)
    Mol, J.H.A. - \ 1995
    Agricultural University. Promotor(en): J.W.M. Osse. - S.l. : Mol - ISBN 9789054854388 - 174
    dieren - relaties - Siluridae - ecologie - diergedrag - gewoonten - Neotropisch gebied - animals - relationships - Siluridae - ecology - animal behaviour - habits - Neotropical Region

    Tropical ecosystems are renowned for their high biodiversity with many closely related species living together. Alpha diversity of tropical freshwater fishes is also extremely high, as exemplified by the cichlid fauna of the Great African lakes and the neotropical characins. Since Hutchinson in 1959 posed his often quoted question: "Why are there so many animals?", factors affecting species diversity have been important subject of study and discussion in ecology. Given the limits of the physical environment, two different biological processes are probably responsible for most of the organization of equilibrial communities: competition and predation. Critics of the view that competition and predation play a major role in structuring communities argued that several factors keep populations below a level where competition or predation could be strong. Reviews of the literature on field experiments designed to demonstrate the influence of competition and predation revealed that only 9% of the studies were conducted in the tropics.

    The tropical rainforest is one of the most stable environments in the world. Temperature and humidity are almost constant, but important fluctuations in the water level of streams and swamps occur. Extreme conditions limiting population densities and leading to the extinction of populations are often hard to imagine. The high number of species will lead to complex biological interactions. More studies on competition and predation in the stable environment of the tropical rainforest are necessary to evaluate the importance of both processes in structuring communities.

    A case study is presented concerning three medium-sized armoured catfishes of the family Callichthyidae: Callichthys callichthys, Hoplosternum littorale and Hoplosternum thoracatum. In order to evaluate the influence of competition and predation on the catfish communities, four factors were investigated in detail: 1) geographical distribution, 2) diet overlap, 3) reproductive seasonality and nest-site differentiation, and 4) predation.

    In Suriname (South America), both C. callichthys and H. thoracatum occur all over the country. Both catfishes are abundant in both coastal plain swamps with standing water and rainforest creeks in the interior with running water. Hoplosternum littorale, on the other hand, is restricted in its distribution to coastal plain swamps. Salinity tolerance experiments demonstrated that one-week old larvae of H. littorale could not survive in electrolyte-poor water (e.g. rain water). The 'clear water' of rainforest creeks in the interior may be compared to slightly contaminated distilled water with very low electric conductivity. Larvae of both C. callichthys and H. thoracatum survived and developed further in rain water. The pattern of distribution in Suriname can be considered as a model of the distribution of the three catfishes in South America. In South America, H. littorale is not only conspicuously absent from clear water streams draining the weathered Precambrium Guyana and Brazilian Shields, but also from 'black water' streams with humic acids and also a low conductivity (e.g. the Rio Negro). Within the Amazon drainage system H. littorale seems restricted to 'white water' streams loaded with Andean sediments and with a higher conductivity than both clear water and black water. In Suriname, actual syntopy of the three species occurs in coastal plain swamps. In rainforest creeks of the interior C. callichthys and H. thoracatum occur syntopically. Consequently interspecific competition among the three callichthyids is possible.

    Analysis of the stomach contents of larvae, juveniles and adults of the three armoured catfishes revealed no significant interspecific differences in the diet of larvae, juveniles and adults. However, ontogenetic differences in diet composition among larvae, juveniles and adults where significant for all three catfishes. Larvae of C . callichthys, H. littorale and H. thoracatum fed almost exclusively on Rotifera, Cladocera and Copepoda. The stomach contents of juveniles were more diverse and included micro-crustacea, insect larvae, aquatic insects and some detritus. Adults ingested large quantities of detritus which probably reflected the inability of large fish to seperate effectively benthic invertebrates from substrate. Chironomid larvae where found in large numbers in the stomach of adult specimens. The short alimentary tract of the three catfishes and the structure of its wall make it improbable that these fishes are able to assimilate detrital nonprotein amino acids. The posterior part of the intestine is thin-walIed and has a respiratory function. The anterior digestive portion is relatively short. Morphologically the three callichthyids are adapted to a benthic way of life and a diet of soft-bodied aquatic invertebrates. The similarity in the diet and their bottomdwelling habit provide the basis for grouping the three armoured catfishes into one ecological guild. Competitive interactions are expected to be potentially strong among members of a guild.

    Male C. callichthys, H. littorale and H. thoracatum construct and guard a floating bubble nest in flooded swamps. Although the habit of constructing a floating bubble nest probably evolved as an adaptation to the oxygen-depleted environment of tropical standing waters, some of the characteristics of the nests of C.callichthys and H. thoracatum may have evolved as a response to the unpredictability of the fluctuations in water level and water velocity in rainforest creeks. The conspicuous nests allow the study of the temporal pattern of breeding, the spatial distribution of the nests and the differentiation of the nest-site microhabitat among the three species. Daily surveys in coastal plain swamps revealed a similar, bimodal breeding season in the three catfishes. Nests were observed in both the short and long rainy season. The bimodal breeding pattern in Suriname is probably related to the unreliability of the rainfall in the short rainy season of December-January. In French Guiana the rains of December-January usually do not fail and an unimodal breeding season of H. littorale is found. Significant differences in nest macrohabitat selection were found among the three callichthyids. Nests of H. littorale were built in herbaceous swamps, while C . callichthys and H. thoracatum nested in swamp forest under trees. The two forest nesting species differed in the microhabitat at the nest site. Nests of C . callichthys were constructed in extremely shallow water and in holes of tree roots and earth. Nest densities in the selected habitat were low in C.callichthys and H. littorale, but relatively high in H . thoracatum. Nest-site differentiation in the rainy season (the main feeding period) may prevent competitive exclusion among the three catfishes.

    The potential predation pressure on eggs, larvae and juveniles of H. thoracatum was estimated by combining laboratory predation rates of 24 predator species (both invertebrates and vertebrates) with the density of the predators in the swamp as determined by chemofishing with rotenone. The contribution of a particular predator species to the total predation pressure on H.thoracatum was determined to a large extent by the density of the predator in the swamp. Seemingly innocuous predators with low or moderate predation rates in the laboratory may be extremely important in the swamp due to their abundance. Smallsized fishes and aquatic invertebrates are probably major predators of early developmental stages of H. thoracatum. The potential predation pressure on eggs is high, but the aggressive nest guarding behaviour of the male catfish and concealment of the nests probably protects the eggs effectively from most aquatic predators. Larvae are not guarded by the male and the potential impact of the 24 predators on the larvae of H. thoracatum is large. Although the experiments were performed with H. thoracatum there is no good reason to expect important differences in predation rates on larvae of the three armoured catfishes. Even if only 2.5 % of the potential predation will be realized due to other prey available, the high mortality of early developmental stages of H. thoracatum (and C. callichthys and H. littorale ) in the swamp could be easily explained as the effect of predation. Potential predation pressure and the number of predators that were able to prey on H. thoracatum sharply declined with increasing age (size) of the juvenile catfish. The heavy armour of bony plates and stout pectoral spines protect older juveniles and adults from most potential predators. The high potential predation pressure in the swamps and the low density of juvenile catfish at the end of the rainy season suggest that predation is important in structuring these catfish communities.

    Although larvae of the three armoured catfishes C. callichthys , H. littorale and H. thoracatum show differences in tolerance to electrolyte-poor water, the three species occur together in coastal swamps. Interspecific diet overlap is very high, and the three catfishes show no differentiation in their breeding season and diel pattern of activity. Ontogenetic changes in the defense mechanisms of armoured catfishes result in a situation in which both predation and competition exert control at different times in the life cycle. Predators probably kill most of the larvae and juveniles, leaving only a few individuals to escape and reach adulthood. If the number of escapes would exceed the number of adult deaths, the populations eventually become sufficiently dense to compete. However, in this situation nesthabitat segregation may prevent competitive exclusion of one of the three species .

    Improving network performance.
    Engel, P.G.H. - \ 1995
    LEISA : ILEIA newsletter for low-external-input and sustainable agriculture 11 (1995)2. - ISSN 1569-8424 - p. 14 - 15.
    informatieverspreiding - verspreiding van onderzoek - agrarische bedrijfsvoering - verbetering - informatie - innovaties - intermenselijke relaties - modernisering - relaties - onderzoek - technologieoverdracht - landbouwvoorlichting - diffusion of information - diffusion of research - farm management - improvement - information - innovations - interpersonal relations - modernization - relationships - research - technology transfer - agricultural extension
    Rapid (or Relaxed) Appraisal of Agricultural Knowledge Systems (RAAKS) is a participatory action-research methodology to improve networking among people and organisations relevant to agricultural innovation. It is put into practice in a programme in 6 Central American countries aiming at improving the relevance and impact of research and extension for small grain producers
    Water depths at the upper boundary for overland flow on small gradients.
    Molen, W.H. van der; Torfs, P.J.J.F. ; Lima, J.L.M.P. de - \ 1995
    Journal of Hydrology 171 (1995). - ISSN 0022-1694 - p. 93 - 102.
    regen - relaties - oppervlakkige afvoer - hellingen - bodemwatergehalte - rain - relationships - runoff - slopes - soil water content
    Invloed van diverse verstoringsbronnen op het gedrag en habitatgebruik van gewone zeehonden : consequenties voor de inrichting van het gebied
    Brasseur, S.M.J.M. ; Reijnders, P.J.H. - \ 1994
    Wageningen : IBN (IBN-rapport 113) - 62
    phocidae - relaties - dieren - mens - adaptatie - milieu - nadelige gevolgen - milieueffect - menselijke activiteit - phoca vitulina - waddenzee - phocidae - relationships - animals - man - adaptation - environment - adverse effects - environmental impact - human activity - phoca vitulina - wadden sea
    Hout is meer dan hout.
    Oldeman, R.A.A. - \ 1994
    Ekoland 14 (1994)3. - ISSN 0926-9142 - p. 16 - 17.
    landbouw - communicatie - bosbouw - informatie - kennis - relaties - symbolen - agriculture - communication - forestry - information - knowledge - relationships - symbols
    A defence is made for more mutual understanding, a sort of common language, between agriculturists, cattle breeders and foresters, since agricultural specialization has become so prominent. In decision making about felling, planting or saving trees, a proper consideration or calculation for each seperate farm is necessary!
    Belangrijke rol voor het agrarisch onderwijs bij de omschakeling van de landbouw.
    Grooters, J.W. - \ 1994
    Agrarisch Onderwijs 36 (1994)10. - ISSN 0925-837X - p. 14 - 16.
    agrarisch onderwijs - modernisering - innovaties - agrarische bedrijfsvoering - onderwijsmethoden - mondelinge communicatie - verbale communicatie - scholen - samenwerking - relaties - organisaties - bedrijven - ondernemingen - agricultural education - modernization - innovations - farm management - teaching methods - oral communication - verbal communication - schools - cooperation - relationships - organizations - businesses - enterprises
    De noodzaak tot herorientatie van de landbouw die vooral een andere houding ten aanzien van het boer-zijn vraagt. Er lijkt in dit proces een belangrijke taak weggelegd te zijn voor het agrarisch onderwijs. In dit artikel wordt verslag gedaan van het laatste deelonderzoek
    Structure and function of soil microarthropod communities
    Siepel, H. - \ 1994
    Agricultural University. Promotor(en): L. Brussaard. - S.l. : Siepel - ISBN 9789090074504 - 136
    bodemfauna - micro-organismen - geleedpotigen - dieren - populatiedichtheid - populatie-ecologie - mortaliteit - populatiegroei - relaties - habitats - overleving - biocenose - ecosystemen - kringlopen - biogeochemie - ecotoxicologie - bioaccumulatie - soil fauna - microorganisms - arthropods - animals - population density - population ecology - mortality - population growth - relationships - habitats - survival - biocoenosis - ecosystems - cycling - biogeochemistry - ecotoxicology - bioaccumulation

    Microarthropod species were classified according to life-history tactics and feeding guilds. Twelve life-history tactics were distinguished, based on well-defined life-history traits like the type of reproduction (thelytoky, arrhenotoky, sexual reproduction), oviposition (semelparity, iteroparity), development, synchronization (of the life cycle with environmental conditions), and dispersal (phoresy, anemochory). Examples are given of the distribution of these tactics among microarthropod species occurring in several biotopes, during decomposition of organic matter, and under several types of disturbance and pollution. Thelytokously reproducing species appeared to have higher numbers at sites with a persistent pollution.

    Feeding guilds were defined on the basis of gut carbohydrase (cellulase, chitinase, and trehalase) activities. Five species-rich guilds were recognized. In the presence of species able to digest the fungal cell-wall next to cell-contents (called fungivorous and herbo-fungivorous grazers), a higher CO 2 evolution during decomposition of pulverized litter was found than in their absence. In the presence of species able to digest cell-contents only (called fungivorous browsers and opportunistic herbofungivores), in such experiments a lower CO 2 evolution was found than in their absence.

    In a simulation model it was tested whether relatively inefficient use of food may be compensated by life-history traits or abilities by which short-term environmental extremes can be overcome. Having the possibility to bridge a relatively long period of food shortage, or withstanding extremes in drought, frost or heat, or having a higher mobility, was indeed shown to result in a better survival of species that use their food relatively inefficiently. This results in the effect that species with different life-history tactics can coexist on the same food sources. Contradictory to the principle of competitive exclusion, species with identical niches may coexist when the mobility of these species is not unlimited.

    Le système d'élevage Peulh dans le sud du Burkina Faso. Une étude agro-écologique du département de Tô (Province de la Sissili).
    Boer, W.F. de; Kessler, J.J. - \ 1994
    Unknown Publisher (Documents sur la Gestion des Ressources Tropicales 4) - 106
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - silvopastorale systemen - bosweiden - bedrijfssystemen - zoötechniek - burkina faso - agro-ecologie - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - silvopastoral systems - woodland grasslands - farming systems - zootechny - burkina faso - agroecology
    Organic carbon turnover in three tropical soils under pasture after deforestation.
    Veldkamp, E. - \ 1994
    Soil Science Society of America Journal 58 (1994). - ISSN 0361-5995 - p. 175 - 180.
    bodem - koolstof-stikstofverhouding - kooldioxide - bosbouw - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - costa rica - soil - carbon-nitrogen ratio - carbon dioxide - forestry - waste land - land use - forests - relationships - deforestation - afforestation - costa rica
    Distribution and multiplication of iris severe mosaic potyvirus in bulbous Iris in relation to metabolic activity : implications for ISMV detection
    Vlugt, C.I.M. van der - \ 1994
    Agricultural University. Promotor(en): R.W. Goldbach; P.M. Boonekamp. - S.l. : Van der Vlugt - ISBN 9789054853220 - 130
    plantenziekten - plantenvirussen - bloembollen - potyvirus - virussen - cellen - relaties - iris - plant diseases - plant viruses - ornamental bulbs - potyvirus - viruses - cells - relationships - iris

    During cultivation of iris, several viruses may cause severe damage like yield reduction and discoloration of the plant. In commercial stocks in the Netherlands virtually all plants are infected with iris mild mosaic virus (IMMV) while iris severe mosaic virus (ISMV) and narcissus latent virus (NLV) can also be present at high incidence. ISMV and IMMV both belong to the genus Potyvirus of the largest plant virus family, the Potyviridae.

    As the quality of virus-free iris is superior and methods are available now to produce and grow virus-free iris for commercial practice, it is of great importance to control the spread of iris viruses. Therefore rapid and reliable assays for the detection of these viruses are needed. In the Netherlands such tests are being developed mainly at the Bulb Research Centre in Lisse. At the start of the research described in this thesis, detection of ISMV in the iris bulb was problematic, in contrast to that of IMMV It has been difficult to detect ISMV reliably in iris bulbs from lifting in late August to planting in October by means of ELISA or electron microscopy.

    The aim of the research was to develop a reliable detection protocol suitable for monitoring ISMV infection, and, to understand the behaviour of this virus in the iris plant, especially the bulb, with respect to the multiplication and movement of the virus in relation to the metabolic activity of the plant. Preliminary results concerning the development of a test protocol are presented in Chapter 2, and further elaborated in Chapter 3, 7 and 8. In Chapters 4, 6 and 7 the behaviour of ISMV in relation to the metabolic activity of the plant is elaborated. In Chapters 5 and 8 a further characterisation of ISMV is presented.

    In freshly-lifted bulbs secondarily infected with ISMV, the virus was not always detected in the basal plate and rarely in bulb scale tissue (Chapter 4), but it gradually became better detectable in the bulb scale tissue when bulbs were incubated during several months at a temperature of circa 17°C (Chapter 2). When a wounding method was applied on the iris bulb by cutting a slice of bulb scale tissue from a side of the bulb, ISMV became readily detectable in all bulbs, though only in tissue adjacent to the cut surface, if the cut bulbs were incubated for three weeks at an optimal temperature of 17-20°C (tested within a range of 5 to 30°C; Chapters 2 and 3). It was concluded that stress followed by a recovery period is favourable for an enhanced detection of the virus. Indeed, high temperature treatment, applied as an alternative stress, also gave rise to improved detection of ISMV (Chapter 3).

    To investigate whether the virus became better detectable by multiplication rather than by modification of the antigenicity of the coat protein, the levels of the viral antigen as well as those of the viral RNA were followed after wounding. From this analysis it was concluded that the increase of the virus titre was due to multiplication (Chapter 4). For the detection of the viral RNA, a cDNA done corresponding to a part of the 3'-terminal region of the ISMV genome was used. The availability of this clone led to the determination of the nucleotide sequence of the ISMV coat protein (CP) gene, thus allowing a definitive classification of the virus. Phylogenetic comparisons of potyviral CP sequences revealed that ISMV is a taxonomically distinct potyvirus not closer related to other bulbous or monocotyledonous infecting potyviruses than to other potyviruses. The sequence data also allowed to conclude that the CP is probably cleaved off from the NIb protein at an unusual glutamine acid-glycine (E/G) dipeptide cleavage site. Furthermore the N-terminus of the CP appeared to be only 15 amino acids long, being the shortest found among potyvirus CPs studied so far.

    Further research on the localisation of the virus after high-temperature treatment showed that the virus was well detectable in the bulb base and usually also in the vascular bundles and surrounding tissue. This suggested that the virus did spread from the basal plate towards the bulb scales. However when the wounded (cut) apical parts of infected, but in ELISA negative reacting, bulbs were incubated at an optimal recovery temperature, the virus became detectable in these upper parts of the bulbs (Chapter 4). Thus, virus must have been originally present in the scales, albeit at a very low and at non-detectable concentration. This provides another indication that multiplication is likely to be the main factor involved in the improved sensitivity of viral detection. It is, therefore, hypothesised that the multiplication is enhanced by increased metabolic activity after stress. A possible correlation between metabolism and ISMV multiplication was further investigated in Chapter 6, with oxygen uptake as a measure for the metabolic activity after application of wounding, high-temperature stress or ethylene treatment.

    An increased level of total oxygen uptake was found after wounding as well as high- temperature treatment, thus positively correlating with the enhancement of ISMV detection. Application of ethylene, an important plant hormone in relation to stress, caused a limited increase in respiration and a slight improvement of ISMV detectability. After wounding, the mitochondrial respiration, the residual respiration and the capacity of the alternative pathway had increased, while after high-temperature treatment there was mainly an increase in residual respiration measured. These findings suggest that increased production of metabolic intermediates, possibly by the pentose phosphate pathway, rather then an increase in energy is important for the observed stress-induced multiplication of ISMV in iris bulbs.

    For the development of a satisfactory test method, it is imperative that virus is reliably detected not only in secondarily infected bulbs but also in primarilyinfected bulbs. To obtain primarily infected bulbs, virus-free plants were mechanically inoculated with ISMV at different times during the growing season. At lifting the level of ISMV in primarily infected bulbs appeared to be dependent on the date of inoculation. Surprisingly, it was found that early infections were scarcely detectable in the bulbs in contrast to late infections. The later in the season infection took place, the better ISMV was detectable in (untreated) bulbs (Chapter 7). Wounding of these primarily infected bulbs generally resulted in an increased detection in bulbs of the early infected plants, but the virus titre in bulbs of late infections decreased. However, these infections were still reliably detectable. Another potential problem for implementation of the developed test for routine use could be the existence of differently reacting isolates of ISMV. In spite of causing slightly different symptoms and serological reactions, all could be detected by the wounding method (Chapter 8).

    The reason why ISMV is so difficult to detect in secondarily infected and in early primarily infected bulbs was investigated further in Chapter 7. The virus titre was monitored in the whole plant, including the bulb, during the growing season for both secondarily and primarily infected plants. The distribution of ISMV in the above-ground parts of secondarily infected as well as primarily infected plants correlated with the nutrient flow via the vascular system. This implied that above-ground parts of secondarily infected plants were totally infected while in primary infections the presence of virus was dependent on the time of infection: during an early infection virus still spread to the upper leaves of the plant and only later to the new bulb, while in late infected plants the virus was found mainly in the new bulb. However, in secondarily infected plants hardly any virus could be detected in the new bulbs at any time during the whole growing season. Besides, the detectability of ISMV in bulbs of early infected plants decreased considerably towards the end of the growing season. This might be explained by assuming that the plant develops a barrier at some time after infection blocking virus avenue to the bulb, or that the virus in secondarily and early primarily infected plants is no longer available for transport anymore (Chapters 7 and 9). It must be concluded that detection of ISMV in these secondarily and early primarily infected bulbs immediately after lifting is unreliable due to impeded import of virus into the bulb.

    Een nieuwe structuur in het agrarisch hoger onderwijs.
    Vries, A.Ph. de - \ 1994
    Agrarisch Onderwijs 36 (1994)7. - ISSN 0925-837X - p. 8 - 11.
    scholen - samenwerking - relaties - organisaties - hoger onderwijs - beroepsopleiding - agrarisch onderwijs - schools - cooperation - relationships - organizations - higher education - vocational training - agricultural education
    De mogelijke hinder van een 25 MW windpark voor vogels op twee potentiele lokaties in Noord - Groningen
    Bergh, L.M.J. van den; Spaans, A.L. ; Winkelman, J.E. - \ 1993
    Wageningen : IBN-DLO (IBN - rapport 016) - 81
    vogels - relaties - dieren - mens - dood - mortaliteit - krachtcentrales - energiebronnen - windmolens - molens - ecologisch evenwicht - schade - nederland - natuur - verstoring - groningen - birds - relationships - animals - man - death - mortality - power stations - energy sources - windmills - mills - ecological balance - damage - netherlands - nature - disturbance - groningen
    Invloed windmolens op vogels
    Forse daling stikstofoverschot op MDM-bedrijven
    Daatselaar, C.H.G. - \ 1993
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 6 (1993)4. - ISSN 0921-8874 - p. 3 - 6.
    duurzaamheid (sustainability) - melkvee - melkveehouderij - voer - mineralen - milieubescherming - milieubeheer - milieu - kwaliteit - boekhouding - bodem - uitspoelen - agrarische bedrijfsvoering - overheidsbeleid - milieubeleid - milieuwetgeving - luchtverontreiniging - bodemverontreiniging - waterverontreiniging - kunstmeststoffen - verliezen - resteffecten - samenwerking - bedrijven - relaties - nederland - sustainability - dairy cattle - dairy farming - feeds - minerals - environmental protection - environmental management - environment - quality - accounting - soil - leaching - farm management - government policy - environmental policy - environmental legislation - air pollution - soil pollution - water pollution - fertilizers - losses - residual effects - cooperation - businesses - relationships - netherlands
    Geschetst wordt hoe de bedrijven binnen het project omgaan met mineralen en welke inspanning dit vraagt bij het management.
    Perspectives pour le développement soutenu des systèmes de production agrosylvopastorale au Sanmatenga, Burkina Faso.
    Hoek, R. van der; Groot, A. ; Hottinga, F. ; Kessler, J.J. ; Peters, H. - \ 1993
    Wageningen : Unknown Publisher (Documents sur la Gestion des Ressources Tropicales 3) - 73
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - silvopastorale systemen - bosweiden - plattelandsplanning - plattelandsontwikkeling - sociale economie - burkina faso - economische planning - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - silvopastoral systems - woodland grasslands - rural planning - rural development - socioeconomics - burkina faso - economic planning
    Soil organic carbon dynamics in pastures established after deforestation in the humid tropics of Costa Rica
    Veldkamp, E. - \ 1993
    Agricultural University. Promotor(en): N. van Breemen. - S.l. : Veldkamp - ISBN 9789054851691 - 117
    plantensuccessie - ontbossing - organische verbindingen - bodem - bodemchemie - graslanden - biocenose - ecosystemen - kringlopen - biogeochemie - bosbouw - woeste grond - landgebruik - bossen - relaties - bebossing - costa rica - lucht - hygiëne - luchtverontreiniging - kooldioxide - plant succession - deforestation - organic compounds - soil - soil chemistry - grasslands - biocoenosis - ecosystems - cycling - biogeochemistry - forestry - waste land - land use - forests - relationships - afforestation - costa rica - air - hygiene - air pollution - carbon dioxide

    Currently, rates of deforestation in the tropics are probably higher than ever before in the past. As a consequence, changes in the earth's physical and chemical environments are proceeding at unprecedented rates. Increasing atmospheric concentrations of CO 2 , N 2 O and other trace gases, caused by enhanced emissions from soils after forest clearing, show that deforestation in tropical areas is of global importance. Recent estimates suggest a net release of carbon from the world's tropics, due to deforestation, of between 0.42 and 1.60 Pg C yr -1(1 Pg = 10 15g) of which 0.1 to 0.3 Pg C yr -1are attributed to decreases in soil organic matter content. This carbon release from tropical areas is second only to the global release from the burning of fossil fuels (which is about 5.3 Pg C yr -1).

    The main objective of this thesis was to quantify the changes in soil organic carbon storage and the resulting release of CO 2 after the conversion of tropical rain forest to pasture on two contrasting soil types in the humid tropics of Costa Rica. To study changes in soil organic carbon storage, sites of an Andisol and an Inceptisol, cleared at different times in the past (deforestation sequences) were compared. A deforestation map, based on aerial photographs from the period 1952 - 1984, was made for a part of the Atlantic Zone of Costa Rica, providing a well documented history of forest clearing. Using GIS techniques, this deforestation map was combined with an available soil map to select the study sites. Analysis of deforestation patterns on the map demonstrated a close relation of deforestation rate with accessibility and soil quality.

    Soil organic matter levels are the result of complex production and decomposition processes. The input of carbon from grass plant roots into the soil was quantified, using pulse labelling with 14C. The pulse labelling experiment revealed that root dry matter production of an improved pasture like Brachiaria (12 Mg ha -1yr -1) was about twice the root production of a low-productive species like Axonopus (6 Mg ha-1 yr-1). Root biomass of Brachiaria was about three times the root biomass of Axonopus due to higher residence time of carbon in the root biomass of Brachiaria as compared to Axonopus . Root exudates of grass plants were found to have a minor direct contribution to the longer term carbon dynamics, either because exudation rate was small or because decomposition was fast and complete.
    Decomposition of soil organic matter was measured using the δ 13C method, which uses differences in natural 13C isotope levels in vegetation (C3 and C4 vegetation) and soil organic matter to calculate changes in soil organic carbon. The method is applicable in soil organic matter studies where a change from C3 to C4 vegetation has occurred (or vice versa). It was demonstrated that for a correct application of the method, detailed information of changes in bulk densities accompanying changes in land use was vital. An uncertainty analysis of the δ 13C method demonstrated that the output of the δ 13C method in soil organic matter studies was highly variable due to variations in the input data. Spatial variability was the main source of the uncertainty in input data. However, variations due to sampling error and short scale variability were considerable and should not be ignored.

    Information on carbon input and decomposition was integrated, using a simple structured soil organic carbon (SOC) model which included carbon isotope fractionation during decomposition and depth dependent decomposition and humification rates. With this model, the observed changes in soil organic carbon and corresponding δ 13C levels during the conversion from a humid tropical forest to a cattle pasture were simulated successfully for the two soil types. With the calibrated model the cumulative net C02 release was calculated. The cumulative net release of CO 2 for pastures with low productive grass species (Axonopus compressus), varied from 31.5 (Humitropept) to 60.5 Mg C ha -1(Hapludand) in the first 20 years after forest clearing. These cumulative emissions could be reduced to 12.0 and 24.7 Mg C ha -1respectively, if higher productive grass species (e.g. Brachiaria dictyoneura ) would be introduced into the area.

    Decomposition rates were strongly influenced by depth. Inclusion of deeper layers in soil organic carbon simulation studies and considering carbon isotopes will probably improve the performance of SOC models in long-term studies.

    Rainfall-runoff model for design flood computation with variable parameters.
    Ignar, S. ; Bogardi, J.J. - \ 1993
    Wageningen : Landbouwuniversiteit Wageningen (Rapport / Landbouwuniversiteit, Vakgroep Waterhuishouding 32) - 20
    analogen - hydrologie - modellen - regen - relaties - analogues - hydrology - models - rain - relationships
    Onderzoek naar samenhang. Landbouwuniversiteit en agrarische hogescholen: samen uit, samen thuis?
    Vries, A.Ph. de - \ 1993
    Agrarisch Onderwijs 5 (1993)14. - ISSN 0925-837X - p. 10 - 13.
    hogere agrarische scholen - universiteiten - hoger onderwijs - beroepsopleiding - agrarisch onderwijs - scholen - samenwerking - relaties - organisaties - veluwe - gelderland - agricultural colleges - universities - higher education - vocational training - agricultural education - schools - cooperation - relationships - organizations - veluwe - gelderland
    Landbouwonderwijs moet imago in kennisnetwerk verbeteren. Huidige beleid is doodlopend spoor.
    Grooters, J.W. - \ 1993
    Agrarisch Onderwijs 35 (1993)18. - ISSN 0925-837X - p. 10 - 13.
    onderwijsplanning - onderwijsbeleid - onderzoek - hogere agrarische scholen - universiteiten - landbouw - verspreiding van onderzoek - informatieverspreiding - technologieoverdracht - scholen - samenwerking - relaties - organisaties - wetenschappelijk onderzoek - wetenschap - landbouwvoorlichting - educational planning - educational policy - research - agricultural colleges - universities - agriculture - diffusion of research - diffusion of information - technology transfer - schools - cooperation - relationships - organizations - scientific research - science - agricultural extension
    Kinetisch gedrag van soja bij warmtebehandelingen.
    Zuilichem, D.J. van; Adriaanse, P.P. ; Hok a Hin, R. ; Poel, A.F.B. van der; Stolp, W. - \ 1993
    Voedingsmiddelentechnologie 21 (1993). - ISSN 0042-7934 - p. 19 - 22.
    chemische structuur - voedselbewaring - voedingsmiddelen - planten - relaties - zouten (activiteit) - sojabonen - zetmeel - thermische energie - thermische eigenschappen - thermodynamica - toxische stoffen - toxinen - chemical structure - food preservation - foods - plants - relationships - salting - soyabeans - starch - thermal energy - thermal properties - thermodynamics - toxic substances - toxins
    Effect of pasture age on soil trace-gas emissions from a deforested area of Costa Rica.
    Keller, M. ; Veldkamp, E. ; Weitz, A.M. ; Reiners, W.A. - \ 1993
    Nature 365 (1993). - ISSN 0028-0836 - p. 244 - 246.
    graslanden - lucht - hygiëne - luchtverontreiniging - stikstofoxiden - bosbouw - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - broeikaseffect - opwarming van de aarde - costa rica - grasslands - air - hygiene - air pollution - nitrogen oxides - forestry - waste land - land use - forests - relationships - deforestation - afforestation - greenhouse effect - global warming - costa rica
    De invloed van de Sep - proefwindcentrale te Oosterbierum (Fr.) op vogels = Impact of the Sep wind park near Oosterbierum (Fr.), the Netherlands, on birds
    Winkelman, J.E. - \ 1992
    Arnhem : DLO-IBN (RIN-rapport 92/2,3,4,5)
    dieren - vogels - schade - dood - ecologisch evenwicht - energiebronnen - mens - molens - mortaliteit - krachtcentrales - relaties - windmolens - nederland - verstoring - friesland - natuur - animals - birds - damage - death - ecological balance - energy sources - man - mills - mortality - power stations - relationships - windmills - netherlands - disturbance - friesland - nature
    Samengaan van land- en bosbouw in bedrijfsverband
    Rijk, P.J. - \ 1992
    Den Haag : LEI-DLO (Mededeling / Landbouw-Economisch Instituut 468) - ISBN 9789052421735 - 59
    bosbouw - landbouw - relaties - weiden - bossen - landbouwgrond - ontbossing - bebossing - nederland - forestry - agriculture - relationships - pastures - forests - agricultural land - deforestation - afforestation - netherlands
    Deforestation trends in the Atlantic Zone of Costa Rica: a case study.
    Veldkamp, E. ; Weitz, A.M. ; Staritsky, I.G. ; Huising, E.J. - \ 1992
    Land Degradation and Rehabilitation 3 (1992). - ISSN 0898-5812 - p. 71 - 84.
    bosbouw - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - fotointerpretatie - luchtfotografie - costa rica - forestry - waste land - land use - forests - relationships - deforestation - afforestation - photointerpretation - aerial photography - costa rica
    Surface sealing and hydraulic conductances under varying-intensity rains
    Giménez, D. ; Dirksen, C. ; Miedema, R. ; Eppink, L.A.A.J. ; Schoonderbeek, D. - \ 1992
    Soil Science Society of America Journal 56 (1992)1. - ISSN 0361-5995 - p. 234 - 242.
    crusts - hydraulic conductivity - infiltration - pedology - rain - relationships - runoff - seepage - simulation - soil - soil micromorphology - korsten - hydraulisch geleidingsvermogen - infiltratie - pedologie - regen - relaties - oppervlakkige afvoer - kwel - simulatie - bodem - bodemmicromorfologie
    In the past, investigations on surface seals developing under simulated rains usually were performed with uniform rainfall intensities. Recent studies, however, showed that varying-intensity rains affect erosion and volumes of runoff. We conducted a study on surface sealing under varying-intensity rains using physical and morphological methods. Four 1-h-duration rainfall patterns were used: S1, S2, S3 and S4, with mean rainfall intensities of 83, 69, 65, and 51 mm h-1, respectively, and highest intensities of 148, 120, 111, and 100 mm h-1, respectively. Two experiments were performed in triplicate: (i) in packed soil columns, pressure heads at 1-cm depth were measured, and runoff (Rt) and wash sediment (St) collected at short time intervals during S1, S3, and S4 patterns; and (ii) packed shallow soil flumes were successively exposed to 10, 15, 30, 40, and 60 min of S2 and S4 patterns, and the surface was then characterized by micromorphological analysis of thin sections (S2) and top-view photographs (S2 and S4). The largest differences between rainfall patterns occurred during the intensity peaks (10–30 min): at the end of these periods, measured surface seal hydraulic conductances (β) attained values of 0.80, 0.25, and 0.51 h-1 for S1, S3, and S4, respectively. These relative β values are thought to be due to partially open surfaces as a result of microrill erosion (S1), complete sealing without erosion (S3), and incomplete sealing (S4). Presented Rt, St, and morphological data support these conclusions. After 5 min of the intensity peaks of S2, surface seals attained maximum observed thickness and minimum macroporosity (>30 µm). Planar voids (>500 µm) were eliminated at this point. Under continuing rain, erosion reduced the seal thickness and increased macroporosity, mainly as planar voids
    Feasibility study on global operational forest cover monitoring network for FAO using satellite remote sensing.
    Burg, G. van der; Venema, J.C. ; Spaa, J. ; Hoekman, D.H. ; Sanden, J.J. van der; Reichert, P.G. - \ 1992
    Delft : BCRS - ISBN 9789054110354 - 105
    bosbouw - remote sensing - luchtkarteringen - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - forestry - remote sensing - aerial surveys - pastures - forests - agricultural land - relationships - deforestation - afforestation
    Compte Rendu Séminaire sur l'aménagement intégré des forêts denses humides et des zones agricoles périphériques.
    Vooren, A.P. ; Schork, W. ; Blokhuis, W.A. ; Spijkerman, A.J.C. - \ 1992
    Wageningen : La Fondation Tropenbos (Tropenbos Series 1) - ISBN 9789051130126 - 307
    bosbouw - oerbossen - tropische regenbossen - vegetatie - agroforestry - agrosilviculturele systemen - landgebruik - tropen - bosbedrijfsvoering - planning - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - ivoorkust - oude bossen - forestry - virgin forests - tropical rain forests - vegetation - agroforestry - agrosilvicultural systems - land use - tropics - forest management - planning - pastures - forests - agricultural land - relationships - deforestation - afforestation - cote d'ivoire - old-growth forests
    Recreatie en toerisme: wiens belang? Over rolverdeling, kwaliteit en duurzame ontwikkelingen.
    Lengkeek, J. - \ 1992
    Wageningen : LU - ISBN 9789067542135 - 131
    regering - vrije tijd - vrijetijdsactiviteiten - recreatiebeleid - nederland - organisaties - beleid - recreatie - relaties - government - leisure - leisure activities - leisure policy - netherlands - organizations - policy - recreation - relationships
    Recreatie en toerisme: wiens belang? Over de beoordeling van ontwikkelingen in de sector recreatie en toerisme.
    Lengkeek, J. - \ 1992
    In: Recreatie en toerisme: wiens belang? : over rolverdeling, kwaliteit en duurzame ontwikkeling / Lengkeek, J., - p. 9 - 46.
    regering - vrije tijd - vrijetijdsactiviteiten - recreatiebeleid - organisaties - beleid - recreatie - relaties - government - leisure - leisure activities - leisure policy - organizations - policy - recreation - relationships
    Evaluatie van de inzendingen voor de ideeenprijsvraag "Bos na 2000"
    Poel, K.R. de; Berg, M.C. van den; Borgesius, J.J. ; Haan - Wiegman, D. - \ 1990
    Utrecht etc. : Directie Bos- en Landschapsbouw [etc.] (Studiereeks bouwen aan een levend landschap nr. 9B)
    bosbouw - bosbedrijfsvoering - regionale planning - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - nederland - forestry - forest management - regional planning - waste land - land use - forests - relationships - deforestation - afforestation - netherlands
    Verstoring van vogels door de Sep-proefwindcentrale te Oosterbierum Fr. tijdens bouwfase en half-operationele situaties, 1984 - 1989
    Winkelman, J.E. - \ 1990
    Arnhem : RIN (RIN-rapport 90/9) - 157
    dieren - vogels - bouwconstructie - bouwnijverheid - gebouwen - civiele techniek - schade - ecologisch evenwicht - hoogte - mens - molens - relaties - structuren - torensilo's - windmolens - nederland - verstoring - friesland - natuur - animals - birds - building construction - building industry - buildings - civil engineering - damage - ecological balance - height - man - mills - relationships - structures - tower silos - windmills - netherlands - disturbance - friesland - nature
    Normen voor draagkracht en oorzaken van draagkrachtverschillen op wegbermen : een bodemfysisch onderzoek langs auto(snel)wegen in Drenthe
    Beuving, J. - \ 1990
    Wageningen : Staring Centrum (Rapport / Staring Centrum 101) - 62
    deformatie - kaarten - regen - relaties - wegenbouw - wegen - wegbermen - oppervlakkige afvoer - hellingen - bodem - bodemkarteringen - nederland - belastingskenmerken (grond) - drenthe - bedijking - deformation - maps - rain - relationships - road construction - roads - roadsides - runoff - slopes - soil - soil surveys - netherlands - bearing characteristics - drenthe - embankments
    The political and administrative context of environmental degradation in South-India : how changes in politics and public administration determine natural resource management by inhabitants of two villages in a drought-prone area
    Douma, Willy ; Kloezen, Wim ; Wolvekamp, Paul - \ 1989
    Leiden : Centre for Environmental Studies - 197
    meteorologie - droogte - bosbouw - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - regering - overheidsorganisaties - overheid - bestuur - participatie - india - bestuursrecht - meteorology - drought - forestry - waste land - land use - forests - relationships - deforestation - afforestation - government - government organizations - public authorities - administration - participation - india - administrative law
    Fysische karakterisering van compactie als gevolg van vegetatieverandering in twee ontbossingssequenties in Costa Rica
    Spaans, E. - \ 1989
    Turrialba [etc.] : CATIE [etc.] (Field reports / Atlantic Zone programme 37) - 27
    bosbouw - bodemdichtheid - bodemverdichting - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - costa rica - forestry - soil density - soil compaction - waste land - land use - forests - relationships - deforestation - afforestation - costa rica
    Rainfall-runoff event model using curve numbers (KINFIL)
    Kovar, P. - \ 1989
    Wageningen : LH (Research report / Wageningen Agricultural University, Department of Hydraulics and Catchment Hydrology 92) - 56
    analogen - hydrologie - modellen - regen - relaties - onderzoek - analogues - hydrology - models - rain - relationships - research
    Mogelijkheid van reductie van de hydraulische capaciteit van regionale RWZI's.
    Witter, J.V. ; Dircke, P. ; Stricker, H. - \ 1989
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 22 (1989). - ISSN 0166-8439 - p. 714 - 720.
    analogen - hydrologie - modellen - regen - relaties - rioolafvalwaterverwijdering - afvalwaterbehandeling - waterzuivering - zuiveringsinstallaties - analogues - hydrology - models - rain - relationships - sewage effluent disposal - waste water treatment - water treatment - purification plants
    Overland flow under rainfall : some aspects related to modelling and conditioning factors
    Lima, J.L.M.P. de - \ 1989
    Agricultural University. Promotor(en): W.H. van der Molen; R.W.R. Koopmans. - S.l. : De Lima - 160
    afvoer - hydrologie - neerslag - regen - relaties - oppervlakteafvoer - infiltratie - hydraulisch geleidingsvermogen - kwel - watererosie - theorie - modellen - windeffecten - analogen - hellingen - computersimulatie - simulatie - simulatiemodellen - discharge - hydrology - precipitation - rain - relationships - overland flow - infiltration - hydraulic conductivity - seepage - water erosion - theory - models - wind effects - analogues - slopes - computer simulation - simulation - simulation models

    This study concerns the theory and some practical aspects of overland flow under rainfall. Of the conditioning factors and processes which govern the generation of overland flow, the following were studied: depression storage, infiltration, morphology and wind. Special attention was paid to wind-driven rain and its effect on raindrops, raindrop splash and wind induced shear stress on the water-air boundary in relation to overland flow.

    The study was carried out by means of laboratory experiments and mathematical modelling, both numerical and analytical. The laboratory experiments included the use of two rainfall simulators and a wind tunnel. Impermeable surfaces (concrete, plastic, plywood and Perspex) and pervious surfaces (loess from Limburg, the Netherlands, and a clay loam from Alentejo, Portugal) were used. A photographic set-up was also used for the assessment of the factors affecting raindrop splash anisotropy.

    In the modelling of the overland flow process, the kinematic wave approach (along with linear and nonlinear assumptions) was used, both for the numerical and analytical solutions. Two numerical models were developed: model KININF for overland flow on an infiltrating surface, and model WROF for overland flow under wind-driven rain. An analytical solution was derived for the rising limb of overland flow over infiltrating surfaces of parabolic shape. The upper boundary conditions used on overland flow studies were also discussed, both with and without wind effects.

    Changes in physical properties of young and old volcanic surface soils in Costa Rica after clearing of tropical rain forest.
    Spaans, E.J.A. ; Baltissen, G.A.M. ; Bouma, J. ; Miedema, R. ; Lansu, A.L.E. ; Schoonerbeek, D. ; Wielemaker, W.G. - \ 1989
    Hydrological Processes 3 (1989). - ISSN 0885-6087 - p. 383 - 392.
    vulkanische gronden - andepts - andosols - bosbouw - woeste grond - landgebruik - bossen - relaties - ontbossing - bebossing - bodemfysica - grondmechanica - humide klimaatzones - tropen - costa rica - volcanic soils - andepts - andosols - forestry - waste land - land use - forests - relationships - deforestation - afforestation - soil physics - soil mechanics - humid zones - tropics - costa rica
    Early stages in cowpea chlorotic mottle virus infection
    Roenhorst, J.W. - \ 1989
    Agricultural University. Promotor(en): R.W. Goldbach; B.J.M. Verduin. - S.l. : Roenhorst - 99
    plantenziekten - plantenvirussen - vigna - vignabonen - virussen - cellen - relaties - plant diseases - plant viruses - vigna - cowpeas - viruses - cells - relationships

    Virussen zijn infectieuze eenheden, bestaande uit nucleïnezuren welke omgeven zijn door een eiwitmantel en eventueel een membraan. Voor wat betreft hun vermenigvuldiging zijn virussen afhankelijk van een levende gastheercel, waarbij ze over het vermogen moeten beschikken deze binnen te dringen, zich erin te vermenigvuldigen en zich vervolgens naar andere cellen te verspreiden.

    Gedurende de laatste decennia is onze kennis over virussen en hun vermogen tot infectie enorm toegenomen. De opkomst van de moleculair- en celbiologische technieken heeft bijgedragen tot een gedetailleerde kennis van zowel de organisatie van het virale genoom, als de mechanismen die aan de expressie en replicatie ervan ten grondslag liggen. Daarnaast hebben biofysische studies informatie verschaft over de structuur en assemblage van het virale deeltje. De kennis over de initiële stadia van het infectieproces, het binnendringen in de gastheercel en de ontmanteling van het virale genoom bleef echter zeer schaars. Het feit dat in veel gevallen slechts enkele virusdeeltjes verantwoordelijk zijn voor infectie heeft vooral bestudering van de initiële interacties tussen virus en gastheercel aanzienlijk bemoeilijkt.

    Dit proefschrift beschrijft het onderzoek verricht aan deze initiële stadia van virusinfecties bij planten. Twee vragen stonden hierbij centraal: (1) hoe en in welke vorm dringt een plantevirus een te infecteren cel binnen en (2) welk mechanisme is verantwoordelijk voor de ontmanteling van het virale genoom? Als model voor dit onderzoek is gekozen voor cowpea chlorotic mottle virus (CCMV) en geïsoleerde cowpea ( Vigna unguiculata ) mesophyl protoplasten. Een aantal eigenschappen van dit modelsysteem zijn weergegeven in de inleiding (Hoofdstuk l).

    Met betrekking tot de initiële interacties tussen virus en gastheercel is voor zowel dierals plantevirussen een beknopt literatuuroverzicht gegeven van de tot nu toe bekende mechanismen (Hoofdstuk 2). Zowel op het niveau van de binding aan het celoppervlak, het binnendringen in de gastheercel, als ook op het niveau van de ontmanteling van het virale genoom, zijn verschillen en overeenkomsten tussen dier- en plantevirussen belicht. De meest opmerkelijke verschillen werden aangetroffen bij de binding en binnendringing van de gastheercel. Is voor de meeste diervirussen binding aan specifieke componenten van de plasmamembraan (receptoren) noodzakelijk voor penetratie, voor plantevirussen lijkt alleen een beschadiging van de plasmamembraan voldoende.

    Om na te gaan in hoeverre ook voor plantevirussen (specifieke) interacties met membraancomponenten van belang zijn voor infectie van de cel, is de binding van CCMV aan cowpea protoplasten -bestudeerd in relatie tot binnendringing en infectie (Hoofdstuk 3). Uit de resultaten van dit onderzoek bleek dat de binding van CCMV aan geïsoleerde protoplasten gebaseerd is op (aspecifieke) elektrostatische interacties, terwijl penetratie afhankelijk is van mechanische beschadiging van de plasmamembraan. Tevens zijn aanwijzingen verkregen dat virusdeeltjes, welke middels endocytose worden opgenomen, niet betrokken zijn bij infectie van de cel. Uit deze gegevens werd geconcludeerd dat alleen die virusdeeltjes, die via membraanbeschadigingen direct in het cytoplasma van de gastheercel terecht komen, verantwoordelijk zijn voor infectie. Ten gevolge hiervan moet worden verondersteld dat ontmanteling van het virale genoom intracellulair plaatsvindt.

    Aangezien voor het tabaksmozaïekvirus (TMV) inmiddels sterke aanwijzingen waren verkregen dat cytoplasmatische ribosomen een rol spelen bij ontmanteling van het genoom middels "cotranslational disassembly", werd nagegaan in hoeverre dit mechanisme ook van toepassing zou kunnen zijn op CCMV. "Cotranslational disassembly" veronderstelt dat ontmanteling plaatsvindt gelijk-tijdig met translatie van het virale genoom, waarbij in het geval van TMV het virusdeeltje vooraf zodanig behandeld moet worden dat het 5'-uiteinde van het RNA beschikbaar is voor initiatie van translatie.

    Door in eerste instantie gebruik te maken van celvrije translatiesystemen werden aanwijzingen verkregen dat ook voor CCMV "cotranslational disassembly" een rol zou kunnen spelen bij de ontmanteling (Hoofdstuk 4). Na toevoeging van intacte virusdeeltjes aan dergelijke systemen werd synthese van virus specifieke eiwitten waargenomen. Bovendien kon de aanwezigheid van translationeel actieve virus-ribosoom complexen worden aangetoond.

    De interactie tussen CCMV en ribosomen werd vervolgens nader geanalyseerd op eiwitniveau (Hoofdstuk 5). Hiertoe werden electroblots van ribosomale eiwitten, gescheiden onder denaturerende omstandigheden, geïncubeerd met virus, en werd het gebonden virus met behulp van immunologische methoden zichtbaar gemaakt. Ongeveer twintig eiwitten, behorend tot zowel de grote als kleine ribosomale subeenheden, bleken virus en/of viraal mantel-eiwit te binden. Dezelfde ribosomale eiwitten bleken eveneens betrokken te zijn bij binding van een aantal andere plantevirussen. Hoewel de beschreven experimenten hierover onvoldoende uitsluitsel geven, zou de waargenomen binding van virus aan deze ribosomale eiwitten op een functionele rol kunnen duiden.

    Naast deze analyse op eiwitniveau is tevens gekeken naar de rol van "cotranslational disassembly" in de ontmanteling van CCMV in vivo (Hoofdstuk 6). Op verschillende tijdstippen na inoculatie werden met CCMV geïnoculeerde cowpea protoplasten gelyseerd en vervolgens geanalyseerd op de aanwezigheid van virus-ribosoom complexen. Inderdaad werden virus-ribosoom complexen aangetroffen, echter in tegenstelling tot in vitro, kon hun translationele activiteit in vivo niet worden aangetoond. Hiervoor wordt een aantal mogelijke verklaringen gegeven. Anderzijds benadrukten ook deze resultaten nogmaals de sterke affiniteit tussen CCMV en ribosomen, en werden aanwijzingen verkregen dat de vorming van virus-ribosoom complexen vooraf zou kunnen gaan aan een eventuele initiatie van "cotranslational disassembly".

    Tenslotte zijn de in de diverse experimentele systemen verkregen gegevens samengevat in een model (Hoofdstuk 7, Figuur l). Dit model beoogt een beeld te geven van die gebeurtenissen die van toepassing zijn op de wellicht minder dan 0,01 % van de virusdeeltjes die verantwoordelijk zijn voor infectie van de cel. Met name daar waar het de interactie tussen virusdeeltje en ribosoom betreft, voorafgaand aan de initiatie van "cotranslational disassembly", bestaan nog veel vraagtekens. Een verdere ontrafeling van deze complexe interacties, alsmede het aantonen van "cotranslational disassembly" van CCMV in vivo. kunnen bijdragen tot een beter begrip van de initiële stadia van virusinfecties bij planten.

    Local level planning for sustainable land use.
    Haeringen, R.P.F. van; Wiersum, K.F. - \ 1989
    Wageningen : Foundation for Dutch Forestry Development Cooperation - 79
    landbouw - ontwerp - ontwikkelingslanden - ontwikkeling - economische ontwikkeling - economie - bosproducten - bosbouw - bossen - landevaluatie - landgebruik - landgebruiksplanning - meervoudig landgebruik - ruimtelijke ordening - planning - programma's - regionale planning - relaties - sociale bosbouw - agriculture - design - developing countries - development - economic development - economics - forest products - forestry - forests - land evaluation - land use - land use planning - multiple land use - physical planning - planning - programs - regional planning - relationships - social forestry
    Bebossing van landbouwgronden : evaluatie - methodiek voor alternatief gebruik van beschikbare landbouwgronden
    Wit, A.P.W. de; Blom, J.C. ; Willems, A.J.H. - \ 1988
    Wageningen : De Dorschkamp (Rapport / Rijksinstituut voor Onderzoek in de Bos- en Landschapsbouw "De Dorschkamp" nr. 541) - 75
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - landbouw - bosbouweconomie - kosten - theorie - berekening - rentabiliteit - bosbouwkundige handelingen - sociale economie - productiekosten - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - agriculture - forest economics - costs - theory - calculation - profitability - forestry practices - socioeconomics - production costs
    A study of upstream boundary conditions for overland flow
    Lima, J.L.M.P. - \ 1988
    Wageningen : Landbouwuniversiteit Wageningen (Research report / Agricultural University, Department of Hydraulics and Catchment Hydrology 89) - 23
    duur - stroming - hydrodynamica - hydrologie - meting - oppervlakteafvoer - neerslag - regen - relaties - oppervlakkige afvoer - snelheid - duration - flow - hydrodynamics - hydrology - measurement - overland flow - precipitation - rain - relationships - runoff - velocity
    Localization of viral antigens in leaf protoplasts and plants by immunogold labelling
    Lent, J.W.M. van - \ 1988
    Agricultural University. Promotor(en): J.P.H. van der Want; B.J.M. Verduin. - S.l. : van Lent - 125
    bromovirus - cellen - vignabonen - cytologie - histologie - methodologie - plantenziekten - plantenvirussen - relaties - technieken - vigna - virologie - virussen - bromovirus - cells - cowpeas - cytology - histology - methodology - plant diseases - plant viruses - relationships - techniques - vigna - virology - viruses

    This thesis describes the application of an immunocytochemical technique, immunogold labelling, new in the light and electron microscopic study of the plant viral infection. In Chapter 1 the present state of knowledge of the plant viral infection process, as revealed by insitu studies of infected cells, is briefly reviewed. Until now, light and electron microscopic studies have merely described morphological changes in cells and tissue as a result of viral infection, but have failed to provide information on the functional role of these structures in the viral infection process and their association with viral components. A common cytopathological feature of many different plant viruses seems to be the induction of membranous vesicles or membranous bodies, which have been implicated in viral replication. However, only in a few cases some evidence was obtained with regard to the Intracellular location of viral replication and the association of replication and membranes. Available cytochemical techniques have apparently failed to provide a tool for the identification of virus particles and virus-encoded proteins within cellular structures. The Impact of a suitable detection techniques to elucidate the molecular processes of viral replication and transport insitu is obvious, as it would link findings obtained by invitro experiments to the events observed in the cell.

    Immunogold labelling seems to provide such a tool for the tracing of antigens in light and electron microscopic preparations of biological specimens. Gold particles are excellent markers for electron microscopy, because of their high electron density which makes them appear as black dots In EM preparations. Furthermore, by a simple silver staining following gold labelling, viral antigens can be dete cted in semi-thin sections with the light microscope. The application of immunogold labelling for the light and electron microscopic localization of antigens is described in Chapters 2, 3, 4, 5, 6 and 7.

    In Chapter 2 the preparation of homodisperse suspensions of colloidal gold particles is described. By adsorption of protein A to the surface of the gold particles, a marker (protein A-gold, pAg) is obtained which can be used for labelling antigen-antibody complexes. The specificity of the technique was demonstrated by gold labelling of antibodies bound to plant viruses in mixed suspensions of two viruses. Each virus was labelled using its homologous antiserum and pAg, and no significant cross-reaction with the other virus occurred. Simultaneous identification of two different viruses (CCMV and SBMV) with similar morphological appearance was achieved by double labelling with pAg-complexes containing gold particles of 7 and 16 nm, respectively. Immunogold labelling of viral antigens in suspension has been applied to distinguish between different serologically related viruses like strains of TMV (Pares and Whitecross, 1982), and the potyvirus sugarcane mosaic virus and maize dwarf mosaic virus (Alexander and Toler, 1986; 1985). A clear advantage of the immunogold labelling over conventional decoration of antigens is that the discrete gold particles allow quantification of the results.

    The immunogold labelling of viral antigen in ultrathin sections of infected protoplasts is described in Chapter 3. Best results were obtained when the protoplasts were only mildly fixed with aldehydes, dehydrated and finally embedded in Lowicryl K4M at -30°C. The antigenicity of viral coat protein was well preserved. A disadvantage of the method is the limited preservation of cell structures, especially membranes due to extraction of lipids. Weibull etal. (1983) reported that approximately 50% of the lipid content of cells may be extracted, despite the low temperatures used in the Lowicryl K4M embedding procedure. Ashford etal. (1986) questioned the low temperature character of Lowicryl embedding, and found that during polymerization of the resin, temperature rises due to the exothermic nature of the reaction. With plant tissue (not protoplasts), low temperature dehydration and infiltration of the embedding resin must be prolonged, to allow sufficient penetration of the chemicals through the thick walls surrounding the plant cells, and this may result in even more extraction than reported by Weibull and colleagues. Rapid dehydration in ethanol and infiltration of plant tissue with a polar resin like LR White at ambient temperatures, therefore, seems to be a good alternative (Newman etal. , 1983; Causton, 1984; Newman and Jasani, 1984).

    Light microscopic localization of viral antigen in semi-thin sections of LR White embedded plant tissue is described in Chapter 6. CCMV was successfully localized in petiolules of systemically inoculated cowpea plants by immunogold labelling and subsequent silver staining (immunogold/silver staining: IGSS). The silver stain could be observed in the light microscope by brightfield, darkfield and phase-contrast illumination. Most sensitive detection, however, was obtained with epi- illumination using polarized light (epipolarization microscopy). Combining epipolarization illumination with brightfield illumination allowed the simultaneous observation of silver stain and cell morphology.

    Immunogold labelling and IGSS in combination with appropriate fixation and embedding of biological specimens, appear to be efficient and simple techniques for the insitu identification and localization of antigens, with many advantages over other immunochemical and cytochemical techniques, like ferritin- labelling, peroxidase-anti-peroxidase, immunofluorescence and autoradiography, which have only incidentally been used in plant virus research. Recently, Patterson and Verduin (1987) have reviewed the literature on the use of immunogold labelling in animal and plant virology, showing numerous fields of applications and discussing progress made in virus research. With respect to the technique the authors rightly concluded that immunogold labelling is a flexible technique with little limitation for the improvement of existing assays and the development of new ones.

    Using immunogold labelling to identify and localize virus particles and coat protein, CCMV- infection in cowpea protoplasts was studied as function of the infection time. Observations with regard to virus entry into protoplasts are reported in Chapter 3. Upon inoculation aggregates of virus particles were observed attached to the plasmamembrane, or sometimes penetrating the plasmamembrane at places where the membrane appeared to be damaged. Virus was also found inside vesicles formed by invagination of the plasmamembrane. These vesicles with inoculum-virus particles were stable over long periods of time. Large vesicles (vacuoles) containing viral antigen were also detected at 24 h post-inoculation in protoplasts which were not infected by CCMV.

    The mechanism by which plant viruses enter their host cells is still disputed (Shaw, 1986). Passage of the plasmalemma by endocytosis was suggested by Takebe (1975), and through pores or lesions by Burgess etal. (1973) and Watts etal. (1981). Our observations do not favour endocytosis to be the mechanism of virus entry leading to infection of the protoplasts as virus containing vesicles are stable. Recently, Roenhorst etal. (1988) presented data supporting a mechanism of virus entry by initial physical association of virus particles with the protoplast membrane and subsequent invasion of virus particles through membrane lesions. Such a mechanism may be also applicable to the cytoplasmic extrusions observed by Laidlaw (1987) after puncturing plant epidermal cells. The author suggested that virus particles may adsorb to the plasmalemma covering the extrusions, which are then withdrawn into the cell. Invasion of whole particles through membrane lesions may then be followed by a uncoating and initial translation (cotranslational disassembly) at the cytoplasmic ribosomes as suggested by Wilson (1985).

    Ultrastructure of RNA-inoculated protoplasts was studied in sections of aldehyde- and osmium-fixed protoplasts (Chapter 4). Cytological alterations attributed to virus infection consisted of dilation of the endoplasmic reticulum (ER) and the formation of vesicles early in infection. Distended ER and vesicles seemed to form a kind of membranous area in the cytoplasm. In protoplasts fixed and embedded in Lowicryl K4M newly synthesized virus particles or coat protein were first localized in restricted areas of the cytoplasm at 6-9 h post-inoculation. The rough appearance of the cytoplasm in these areas suggested the presence of membranous structures like observed in osmium-fixed protoplasts. However, due to poor membrane preservation in Lowicryl embedded material this could not be proven. Within one protoplast several of these labelled areas were identified. At later stages of infection viral antigen was located throughout the cytoplasm, but also in the nucleus and in particular the nucleolus. No viral antigen was detected in or specifically associated with chloroplasts, mitochondria, microbodies and vacuoles. The specificity of gold labelling was demonstrated by quantification of the labelling density on sections of infected and non-infected protoplasts. These results indicate that CCMV coat protein synthesis and virus assembly take place in the cytoplasm of plant cells, but the involvement of cellular structures, in particular membranes, remains to be established. Protein synthesis and virus assembly may occur in certain restricted sites (compartments) in the cytoplasm possibly formed by the membranous bodies. Compartmentalization of the cytoplasm, creating different environments in the cell, may explain the occurrence of both disassembly and assembly in the same cell, and furthermore account for the phenomenon of specific assembly of viral RUA and homologous coat protein in cells infected with two related viruses like CCMV and BMV (Sakai etal. , 1983 ; Zaitlin and Hull, 1987). Whether RNA-replication also occurs in the same location as coat protein synthesis and virus assembly could be established by localization of non-structural virus encoded proteins involved in viral replication. However, antisera against these products of the CCMV-genome were not available. The function of CCMV coat protein or virus in the nucleus and especially the nucleolus is not known. Coat protein may have an affinity for ribosomal proteins and/or fulfill some functional role in the viral replication. Kim 1977 described the occurrence of filamentous inclusions (FI) in the nucleus often associated with the nucleolus. These FI were not found in the nuclei of cowpea protoplasts (this study) or tobacco protoplasts (Burgess etal. , 1974), but may be formed later in the infection by excess coat protein. Bancroft etal. (1969) showed the ability of CCMV-coat protein to form narrow tubules under specific conditions. The (FI) described by Kim (1977) may represent this type of coat protein aggregation, although the chemical composition of the (FI) is not yet known.

    In Chapter 5 preliminary observations are reported on the localization of sites of CPMV replication in cowpea protoplasts, by in situ detection of coat proteins and non-structural proteins involved in viral replication and proteolytic processing. With regard to virus entry and subsequent locations of inoculum virus inside vesicles, similar phenomena were observed as in infection with CCMV. Infection of CPMV generates large inclusion bodies in the cytoplasm, consisting of membranous vesicles with fibrillary material and adjoining amorphous electron-dense material which have been observed as early as 12 h post- inoculation. Virus particles and/or coat protein were first detected 24 h after inoculation throughout the entire cytoplasm and in between the membranous vesicles and electron dense material. The 24K, 170K and their precursor proteins were exclusively localized in the electron dense material and not in association with the membranous vesicles or any other location in the cell. These results show that the electron-dense material consists at least in part of CPMV-encoded non-structural proteins and may represent a site for accumulation of non-functional proteins. The membranous vesicles have been implicated in viral RNA synthesis (Goldbach and Van Kammen, 1985). The failure to detect non- structural proteins in association with these membranes may be explained by either a low concentration of these proteins at the site of replication or by extraction of these proteins during the fixation and embedding procedure, despite the low temperature.

    With IGSS the distribution of CCMV in cowpea plants was monitored at different times after systemic inoculation according to Dawson and Sehlegel (1976) (Chapters 6 and 7). No virus was detected at the time of temperature shift (t=0) in petiolule and leaves of plants subjected to 3 days of differential temperature treatment. Virus was first localized in phloem parenchyma cells of petiolule and veins at t=3 h and from there it spread to neighbouring tissues. Twenty four hours after systemic inoculation virus was located in the phloem, bundle sheath, cortex, but also in the cambium and some xylem cells. These results show that CCMV is transported from the inoculated primary leaves to the secondary leaves through the phloem, apparently following the route of metabolites. This finding is in agreement and further supports the generally accepted concept of plant virus long-distance transport through phloem. tissue (Matthews, 1982; Atabekov and Dorokhov, 1984). The failure to detect CCMV in differentiated sieve elements may indicate that the form in which the infectious entity is transported is another than virus particles (Atabekov and Dorokhov, 1984), or that the amount of virus transported through the sieve elements is below detectable levels. The true character of the synchrony of infection of leaf mesophyll cells obtained by differential temperature treatment is disputed. Infection of mesophyll tells may have been accomplished after shifting the plants to higher temperature by fast transport of infectious particles from the vascular tissue, as was also suggested by Dorokhov etal. (1981).

    For the first time a suitable method for localization of antigens is available, which can be routinely applied for both light and electron microscopic study of the plant viral infection process. The application of the gold labelling technique in the localization of viral structural and non-structural proteins has been demonstrated, using CCMV- and CPMV-infections of plant cells as model system.

    With regard to the technique, future work must be done on the improvement of the preservation of cellular structures, especially membranes, as these appear only poorly in Lowicryl embedded plant tissue even with dehydration, infiltration and polymerization at low temperatures. Alternatives, may be found in cryofixation and cryosectioning or freeze-substitution techniques.

    With regard to the study of the plant viral infection process, the localization of virus-encoded proteins involved in replication and transport, but also the localization of plant viral nucleic acids by insitu hybridization, will contribute to the understanding of the mechanisms underlying these events. New biochemical techniques like the production of infectious transcripts from cloned viral cDNA (Ahlquist etal. 1984) enabling genetic manipulation of the viral genome, and integration of plant viral genes into the plant genome (Gardner etal. , 1984; Abel etal. , 1986) will supply future model systems for the study of virus-host interactions.

    Zorg, zorgelijk, zorgwekkend?
    Weeda, C.J. - \ 1987
    Tijdschrift voor huishoudkunde 8 (1987)1. - ISSN 0169-1295 - p. 1 - 3.
    lerarenopleidingen - huishoudkunde - huishoudonderwijs - echtelijke verhouding - mannen - relaties - onderwijzen - vrouwen - schoolvakken - educational courses - home economics - home economics education - marital interaction - men - relationships - teaching - women - subjects
    Bespreking van verschillende zienswijzen m.b.t. het vak 'Verzorging' in het onderwijs
    Virus-membrane interactions : spectroscopic studies
    Datema, K.P. - \ 1987
    Agricultural University. Promotor(en): T.J. Schaafsma; M.A. Hemminga. - S.l. : Datema - 149
    bacteriofagen - biologie - cellen - bestraling - membranen - plantenvirussen - straling - relaties - virussen - bacteriophages - biology - cells - irradiation - membranes - plant viruses - radiation - relationships - viruses

    In this thesis some new aspects of the infection process of nonenveloped viruses are reported. The interaction of a rod-shaped (TMV) and three spherical (CCMV, BMV, SBMV) plant viruses, of the filamentous bacteriophage M13, and of their coat proteins with membranes have been investigated. A comparison is made between the infection mechanisms of these non-enveloped viruses.


    All plant viruses studied interact with membranes. This is demonstrated by turbidity measurements of small unilamellar vesicles with different surface charges (chapter 2). The interaction is either electrostatic or hydrophobic.

    Neutral vesicles always interact with viral capsids by indirect hydrophobic interaction. On the other hand, charged vesicles always interact with opposite charges at the capsids by electrostatic interaction. The location of the coat protein after interaction has been determined to test Durham's model for plant virus infection, in which the coat protein becomes an integral membrane protein, similarly as for M13 infection. The results indicate that as a result of the interactions, multilamellar vesicles are formed, containing all the protein in case of electrostatic interaction. The coat protein is associated at the bilayer surface. However, after hydrophobic interaction no protein is found in the multilamellar vesicles. For the latter type of interaction a mechanism is proposed, in which the coat protein behaves as a catalyst, only enhancing the rate of fusion and multilamellar vesicle formation. Since in either case no lipid-protein complex is formed, that is stabilized by direct hydrophobic lipid-protein interactions, Durham's model for plant virus infection is very likely to be incorrect.

    The recently proposed co-translational disassembly model for plant virus infection, in which the viral particle dissociates during translation of its RNA by the host ribosomes, does not include a specific role for membranes during disassembly. However, before the co-translational disassembly takes place, the particles need to be destabilized. At this moment no specific mechanism for this process has been proposed. Also the fate of the coat protein after particle disassembly remains unspecified in any model, with exception of Durham's model. The observed electrostatic interaction at the bilayer surface (e.g. with the N-terminal arm of the coat proteins, released upon assembly may play a significant role in the infection mechanism.

    From the experiments described in this thesis no results contradictory to co-translational disassembly have been found. Therefore, to our present opinion, the best model for plant virus infection is the co-translational disassembly model. In this view it is assumed implicitely that the virus particles arrive intact in the cytoplasm, for example by passage through the cell wall and the plasma membrane by local, transient wounding.


    M13 coat protein has been incorporated as an intrinsic protein in micelles and model membranes (chapter 3-4). The secondary structure of coat protein in SDS micelles is, predominantly α-helix (60%), while in membranes (DMPC/DMPA 80/20 w/w) the structure is entirely β-structure.

    In micelles at high detergent protein ratio the protein is dimeric with the central core in β-structure. The termini of the coat protein (30 residues or 60%) are in α-helix structure. The dynamics of the micellar system, investigated by time-resolved fluorescence anisotropy measurements, is characterized by rotation of the complex on the nanosecond timescale (10 ns at 20°C) and additional mobility of the Trp-26 sidechain on the subnanosecond timescale (0.5 ns). The complex has a temperature dependent overall rotation, that satisfies the Stokes-Einstein relation for spherical rotation. From this dependence it has been determined that the complex consists of two coat protein molecules and approximately 57 SDS molecules.

    In membranes, regardless of the lipid to protein ratio, the coat protein Is aggregated. This is concluded from three independent measurements. Fluorescence anisotropy decay measurements indicate that the single tryptophan-26 in the hydrophobic core is highly ordered on the nanosecond timescale in liquid-crystalline bilayers, whereas the surrounding lipids are not. 2H NMR measurements indicate that all the exchangeable sites at the backbone are ordered on the microsecond timescale. Both results are consistent with protein aggregation. Finally, the fraction of motionally restricted lipid, determined from spin label ESR is too low for a monomeric state of the coat protein in the membrane, also in agreement with protein aggregation.

    The state of the M13 coat protein in model membranes used in the experiments of this thesis is therefore best described as a β- polymeric state. Within the polymer the orientation of the coat protein is unknown. For comparison, invivo , the coat protein in the E . coli cytoplasmic membrane is known to be oriented. Its secondary structure and state of aggregation, however, are up to now unknown.


    In model membranes also the effect of M13 coat protein incorporation on the lipids has been investigated (chapter 4). Upon introduction of coat protein in the membrane as an intrinsic protein a fraction of the lipid molecules becomes motionally restricted.

    The spin labelled phospholipids show a difference in their selectivity for the coat protein: cardiolipin = phosphatidic acid>>stearic acid phosphatidylserine = phosphatidylglycerol>>phosphatidylcholine phosphatidylethanolamine. The selectivities found are related to the composition of the target E . coli cytoplasmic membrane. Typically, neutral phosphatidylethanolamine accounts for 74% of the lipid in the membrane, constituting the bulk of the lipid, while phosphatidylglycerol is present for 19% and cardiolipin for 3%. The high selectivity of cardiolipin for the coat protein forms direct, biophysical evidence for a previously suggested molecular association of cardiolipin with the coat protein. This was concluded from an increase in the cardiolipin synthesis after infection of E . coli by M13. No increase in phosphatidylglycerol synthesis, the major negatively charged lipid, is observed after infection.

    Using selectively deuterated palmitic acid as probe lipid, spectral broadening has been observed in presence of M13 coat protein. This result, as well as the ESR results, agrees with a two-site exchange model for the probe lipid between sites in the bulk of the membrane and motionally-restricted sites at the protein. The exchange rate is fast on the nanosecond timescale of the ESR technique, but slow on the microsecond timescale of the 2H NMR technique. The exchange rate of 10 +7Hz, deduced from simulation of the spin label ESR spectra, is in excellent agreement with these upper and lower limits.

    The effect of intensification of shifting cultivation in Africa on stabilizing land-use and forest conservation.
    Wiersum, K.F. - \ 1986
    Netherlands Journal of Agricultural Science 34 (1986)4. - ISSN 0028-2928 - p. 485 - 488.
    zwerflandbouw - bosbouw - landgebruik - pachtstelsel - bebossing - weiden - bossen - landbouwgrond - relaties - ontbossing - afrika - ruimtelijke ordening - zonering - shifting cultivation - forestry - land use - tenure systems - afforestation - pastures - forests - agricultural land - relationships - deforestation - africa - physical planning - zoning
    An example of a rainfall-runoff model for design flood computation.
    Ignar, S. - \ 1986
    Wageningen : Landbouwuniversiteit Wageningen (Publication / Vakgroep Hydraulica en Afvoerhydrologie. Landbouwuniversiteit 74) - 26
    analogen - hydrologie - wiskundige modellen - modellen - operationeel onderzoek - regen - relaties - analogues - hydrology - mathematical models - models - operations research - rain - relationships
    Onderzoek naar de mogelijkheden voor houtproduktie op braakliggende terreinen in het stedelijk gebied : een case-study in Leusden
    Leek, N.A. ; Kuijk, M.M.A. van; Schoenfeld, P.H. - \ 1985
    Wageningen : De Dorschkamp (Rapport / Rijksinstituut voor Onderzoek in de Bos- en Landschapsbouw "De Dorschkamp" no. 398) - 43
    bosbouw - weiden - bossen - landbouwgrond - relaties - ontbossing - bebossing - woeste grond - landgebruik - bosbouweconomie - kosten - theorie - berekening - rentabiliteit - groene zones - heggen - beplanten - aanslaan van het gewasbestand - geografie - steden - stedelijke gebieden - nederland - gemeenten - utrecht - forestry - pastures - forests - agricultural land - relationships - deforestation - afforestation - waste land - land use - forest economics - costs - theory - calculation - profitability - green belts - hedges - planting - stand establishment - geography - towns - urban areas - netherlands - municipalities - utrecht
    Meer, Q.L.Th. van der - \ 1985
    [Wageningen] : L.H. - 70
    onderwijs - gezinnen - groepen - menselijke relaties - individuen - psychologie - relaties - onderzoek - sociale klassen - sociale structuur - sociale relaties - education - families - groups - human relations - individuals - psychology - relationships - research - social classes - social structure - social relations
    Socio-culturele structuur en innovatie : een structuur-vergelijkend onderzoek naar adoptie van family planning in de periode 1969 - 1973 door Sundanese echtparen in twee rurale gemeenschappen op West-Java
    Norren, B. van - \ 1985
    Landbouwhogeschool Wageningen. Promotor(en): R.A.J. van Lier. - Wageningen : Van Norren - 533
    geboortecijfers - contraceptie - culturele verandering - culturele ontwikkeling - cultuur - demografie - gezinsplanning - java - echtelijke verhouding - mannen - relaties - plattelandsgemeenschappen - sociologie - vrouwen - getrouwde personen - birth rate - contraception - cultural change - cultural development - culture - demography - family planning - java - marital interaction - men - relationships - rural communities - sociology - women - married persons

    This publication contains a comparative study of socio- cultural influences on the process of family planning adoption during the period 1969-1973 in two rural communities in the regency of Bandung, West Java, Indonesia. One community, to be called Cianyar, is a ward in an agrarian village, while the other, Citonggoh, constitutes a large dairy and vegetable farm. A few hundred people live in each community.

    The book consists of two parts. In Part One. "The Theoretical Framework", a research model and two research questions are introduced. In the model society is viewed as a tension system of elements which interact on two structural levels: a basic structure of elements from which strong stucturing influences on other elements emanate, and a derived structure of elements which constitutes itself as a reaction upon structuring influences from the basic structure. In the section of society studied, namely the participation system of family planning acceptors and relevant others. the basic structure is thought to consist of four substructures: a material, a social, a cultural and a psychic substructure. The derived structure is thought to consist of the network and the definitions of the situation of acceptors and relevant others. The adoptions of family planning themselves constitute the third level of the research model. On the basis of this model we have formulated as our first research question the task to explain comparatively observed adoptions of family planning in terms of the two categories of network and definitions of the situation as the derived structure of the participation system, and subsequently to explain the network and the definitions of the situation themselves in terms of the four basic substructures of the participation system (chapter 1).

    In chapter 2 the elements constituting the four basic substructures are introduced and specified. Among other things the cultural ideal of the authoritative-harmonic community is mentioned and defined. The concepts of substrate (= the division of the scarce means of property, power, knowledge and strategic contacts among the community members), social position (= an actor's disposal of these scarce means) and social class (= a category of actors with corresponding social positions) are introduced. Subsequently the community is defined as consisting of three social classes: a higher, a middle and a lower class. In order to explain observed differences between the derived structures of Cianyar and Citonggoh, four basic structural elements with very different values or forms in the two communities have been selected. These are (1) the material element of infrastructural access to the family planning clinic, (2) the social element of substrate, (3) the social element of presence of factions in the community and (4) the psychic element of type of leadership exercised in the community.

    In chapter 3 the elements of the two categories of network and definitions of the situation of the derived structure are introduced and specified.

    In the fourth and concluding chapter of Part One the second research question is introduced as an attempt to typify observed adoptions of family planning as modern or not modern on the basis of a clearly defined concept of (individual) modernization. In order to distinguish adoptions which are "really" modern from adoptions which are only "apparently" modern, the concept of pseudo-modernization is introduced.

    In Part Two, "Data and Interpretation", the two research tasks are separately carried out, the first one by successively analysing the adoption processes of Cianyar and Citonggoh in a directly comparable way in accordance with the research model (chapters 5 - 8 and 9 - 13), and the second one by typifying the observed adoptions of Citonggoh and Cianyar as modern or pseudo-modern in accordance with the concept of modernization (chapter 14). In the conclusions of the study (chapter 15) the results of the two research questions are logically and empirically combined.

    Cianyar (ch. 5-8)

    The circumstances of the fieldwork in the ward Cianyar of the village Ciendah are briefly discussed in chapter 5. In chapter 6 the political history of the village Ciendah during the period 1950-1975 is treated as a continuous contest for village power between two groups in the village: a moderately progressive group of village officials and school teachers and their following, headed by the relatively rich family of the village head, and a conservative group of orthodox local religious leades and their following, headed by one relatively rich family also. During this period of 25 years all major village offices were continuously held by members of the former group, the latter being

    continuously in political opposition. It is shown that during the whole period the willingness of orthodox leaders to cooperate with village officials in implementing government development programs varied inversely with their momentary political power in the village.

    In chapter 7 the composition of the basic structure of Cianyar is discussed. In (anticipated) comparison with Citonggoh it is shown that Cianyar is characterized by bad infrastructural access to the family planning clinic, a poly-pyramidal substrate (by which is meant unequal division of the four scarce means among the community members and the concentration of these means in the hands of various individuals from different social and occupational categories), presence of an orthodox faction in the community and absence of charismatic leadership.

    In the following chapter 8 the composition of the derived structure is dealt with by means of an analysis of the local family planning programme and its development over time. The social and class positions of all actors studied were determined. The contents of the programme, its implementation, and the reations of receptors (eligible couples) were separately discussed, the essentials of which are summarized below.

    (1) For several years the orthodox leaders dominated a public opinion which strongly condemned family planning. Mainly because in 1972 the orthodox leaders quite suddenly lost their (political) power in the community, could public opinion quickly change from strongly anti- to moderately in favour of family planning.

    (2) Under the strongly limiting conditions of a poly-pyramidal substrate, presence of an orthodox faction and lack of charismatic leadership qualities, the most important executors of the programme, the ward head of Cianyar and his wife themselves, chose for cautious manoeuvring. They only approached couples with two or more children among the village poor, in particular those working as day labourers on their rice fields. Only after public opinion had changed did they start motivating couples belonging to the orthodox community. The ward heed almost exclusively motivated men, his wife almost exlusively women. Usually they cautiously spoke of family planning as a modern means for spacing births only. In terms of our own typology of informal leadership positions (introduced in Part One) the ward head and his wife behaved as advisors towards their receptors.

    (3) Within the group of non-orthodox couples of Cianyar the adoption process started early 1970 among the school teachers of the higher class. One and a half year later (mid 1971) the process started among the beca drivers, small farmers and small officials of the middle class, and three months later (end 1971) it commenced among the agricultural labourers and plaiters of bambu walls of the lower class in the community. So within the non-orthodox group of the community the adoption process commenced in all three social classes well before public opinion started to change (1972). Within the group of orthodox couples the process started relatively late (mid 1972) among the larger farmers and traders of the higher class and the beca drivers of the middle class. Six months later (beginning 1973) the process commenced among the agricultural labourers and plaiters of the lower class. So within the orthodox group of the community the adoption process started in all three social classes only after public opinion had commenced to change(1972). At the end of chapter 8 it is concluded that, because of the motivating activities of the ward head and his wife, in both groups of the community the adoption process among the couples of the middle and the lower classes has been advanced and accelerated in time.

    Citonggoh (ch. 9-13)

    After a brief discussion of the circumstances of the fieldwork in Citonggoh (chapter 9) the recent history and the organizational structure of the enterprise are described in chapter 10. From mid 1969 till the end of 1973 the enterprise was run by a new Indonesian director who succeeded in making the farm profitable again after near bankruptcy in 1968.

    In chapter 11 the composition of the basic structure of Citonggoh is discussed. In comparison with Cianyar it is shown that Citonggoh is characterized by good infrastructural access to the family planning clinic. a mono-pyramidal substrate (by which is meant concentration of the four scarce means in the hands of one person, the director), absence of (orthodox) factions in the community, and exertion of charismatic leadership, again by the director. It is also shown that the families of nearly all employees - that is director, staffmembers, foremen and labourers - live within the area and in the houses of the enterprise.

    In chapter 12 the character of the director's leadership and power and its development over time are studied by means of an analysis of the contents, implementation and results of a large number of his policy measures. Special attention is given to his interventions pertaining to age at marriage, polygyny, divorce, childbirth and other aspects in the realm of private and family life of his subordinates. Among other things the conclusion is drawn that the director exerted authoritative as well as authoritarian leadership. As an authoritative leader who provides quidance on the basis of exceptional qualities only, the director disposed of his disproportionately large (modern) knowledge and of his charismatic personality. As an authoritarian leader who expects obedience. he could (if he wished) make use of several formal sanctions (like prohibiting to make use of the clinical facilities of the enterprise, prohibiting to live on its area and the very heavy sanction of dismissal) and also of several informal sanctions (like making public personal matters of subordinates).

    In chapter 13 the composition of the derived structure of Citonggoh is dealt with by means of an analysis of the director's family planning programme and its development over time. The essentials of the programme's contents, its implementation and reactions of receptors are summarized below.

    (1) The director considered family planning as an excellent modern means for couples to plan births in all three phases of the family cycle: for young couples to delay the birth of their first child, for couples with one or more children to space the births of additional children, and for couples who had already reached or exceeded their desired number of children, to stop bearing children. Secondly. he felt that all fecund couples of Citonggoh irrespective of one's phase in the family cycle should become acceptors.

    (2) The three conditions of a mono-pyramidal substrate with power being concentrated in the hands of the director, the latter's charismatic personality, and absence of an oppositional (orthodox) faction in the community offered the director as head of his own family planning programme ample opportunity to enforce acceptance by employing the formal and informal sanctions mentioned. In his position of powerful and charismatic leader the director chose for a strategy of differential pressure. All couples who in his opinion could easily understand family planning because they were well educated were not approached. The great majority of these couples belonged to the higher class and higher middle class of the community. All others, the great majority of whom were couples of the lower middle and lower class, were motivated by means of "active persuasion" as the director put it himself, by which he meant: incessant and intensive personal motivation without using any means of coercion. Those who (silently) refused were called to the office to be persuaded again. And again and again if necessary, untill they finally decided to accept. Put in our own terminology this means, that from the motivating activities of the director two influences emerged: on the one hand a real-modern influence because of his incessant efforts to explain family planning to his receptors in terms of the culture concept of rational control of one's own life situation, and on the other hand a dual, classdifferentiated pseudo-modern pressure. This pressure was a double one, because it was authoritative as well as autoritarian (imposing something and at the same time concealing possible sanctions is actually a form of intimidation), and it was class-differentiated because couples belonging to different classes were differentially exposed. In the execution of his family planning programme the director closely cooperated with the nurse of the enterprise. It was the nurse who located potential acceptors and kept track of all motivated couples. Together the director and the nurse performed an a very efficient team.

    (3) The adoption process in Citonggoh started shortly after the beginning of the programs among the couples of the middle and the lower classes, by the end of 1969. Among the (young) couples of the higher class, who could decide in freedom, the process started relatively lare (mid 1971). During the period 1969-1973 nearly all potential acceptors of Citonggoh had accepted family planning. At the end of chapter 13 it is concluded that, because of the motivating activities of the director of the enterprise, the adoption process among the couples of the middle and lower classes has been advanced and accelerated in time.

    In chapter 14 the hypothesis is tested that social pressure from authority or public opinion leads to pseudomodernization. The hypothesis is only slightly confirmed. Only three cases of pseudomodernization in its full extent were encountered in Cianyar, none in Citonggoh. In Citonggoh pseudo-modernization only seems to have occured a few times as an aspect of real-modern adoption. These and other observations led to the conclusion that in alle three social classes of both communities the great majority of fecund couples possesed an unespectedly strong modern mentality in matters concerning planning births of children.

    In chapter 15 the theoretical essentials of the comparative study are restated and several theoretical conclusions drawn, the most important one being recapitulated here: The community leaders of Cianyar and Citonggoh have executed their family planning programmes on the same cultural basis of a twofold ideal of real modernization and exertion of leadership in accordance with the ideal of the authoritativeharmonic community. Because of the structuring influences of four basis structural elements with very different values and forms in the two communities, the two programmes have been very different in their contents and implementation. However, probably due to the unexpectedly strong modern mentality among the couples of all three social classes in both communities both programs have essentially had the same effect of advancing and accelerating the adoption process among the couples of the middle and lower classes.

    Leefvormen en mogelijk beleid
    Hoog, C. de - \ 1985
    In: Gezin : ideaal of alternatief? : waardering van het gezin / de Hoog, C., Musschenga, A.W., Saal, C.D., - p. 106 - 121.
    relaties - sociologie - verwantschap - gezinnen - overheidsbeleid - bestuur - samenwoning - relationships - sociology - kinship - families - government policy - administration - cohabitation
    Kansen en beperkingen voor de realisering van andere leefvormen worden nagegaan . Aangegeven wordt hoe het overheidsbeleid hierop adequaat zou kunnen inspelen
    Hoog, C. de - \ 1984
    In: NITHOO : nieuwe inventarisatie toegepaste huishoudwetenschappen, onderzoek en onderwijs / van Leeuwen, H., Ruiter, C., Guenther, H., Den Haag : NITHOO-VUGA - p. A71 - 4.
    demografie - echtscheiding - huwelijk - relaties - statistiek - samenwoning - gebruiken - personen - demography - divorce - marriage - relationships - statistics - cohabitation - customs - persons
    Wie trouwt met wie, en wie gaat met wie samenwonen
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