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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    Conservation and utilization of natural resources in the East Usambara forest reserves: conventional views and local perspectives.
    Kessy, J.F. - \ 1998
    Wageningen : Wageningen Agricultural University (Tropical Resource Management Papers 18) - ISBN 9789054858096 - 168
    bosbouw - bossen - natuurreservaten - natuurbescherming - bosbouwkundige handelingen - sociale economie - natuurlijke hulpbronnen - landgebruik - pachtstelsel - bebossing - tanzania - bosproducten anders dan hout - nationaal vermogen - forestry - forests - nature reserves - nature conservation - forestry practices - socioeconomics - natural resources - land use - tenure systems - afforestation - tanzania - non-wood forest products - national wealth
    Groei en groeiplaats van de zomereik, de wintereik en de Amerikaanse eik in Nederland
    Burg, J. van den - \ 1997
    Wageningen : IBN-DLO - 104
    bosbouw - standplaatsfactoren - bepaling van groeiplaatshoedanigheden - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - bomen - nederland - quercus robur - quercus petraea - quercus rubra - forestry - site factors - site class assessment - silviculture - forestry practices - growth - environmental factors - trees - netherlands - quercus robur - quercus petraea - quercus rubra
    Groei en groeiplaats van de zwarte els en van de witte els in Nederland
    Burg, J. van den - \ 1997
    Wageningen : IBN-DLO - 57
    bosbouw - standplaatsfactoren - bepaling van groeiplaatshoedanigheden - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - bomen - nederland - alnus glutinosa - alnus incana - forestry - site factors - site class assessment - silviculture - forestry practices - growth - environmental factors - trees - netherlands - alnus glutinosa - alnus incana
    Groei en groeiplaats van de beuk in Nederland
    Burg, J. van den - \ 1997
    Wageningen : IBN-DLO - 60
    bosbouw - standplaatsfactoren - bepaling van groeiplaatshoedanigheden - bomen - bodemkarteringen - kaarten - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - nederland - fagus sylvatica - forestry - site factors - site class assessment - trees - soil surveys - maps - silviculture - forestry practices - growth - environmental factors - netherlands - fagus sylvatica
    Groei en groeiplaats van de grove den en de Corsicaanse den in Nederland
    Burg, J. van den - \ 1997
    Wageningen : IBN-DLO - 90
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - bepaling van groeiplaatshoedanigheden - bomen - nederland - forestry - silviculture - forestry practices - growth - environmental factors - site class assessment - trees - netherlands
    Trends in het ecologisch functioneren van bossen
    Bouwma, I.M. ; Olsthoorn, A.F.M. - \ 1997
    Wageningen : IBN-DLO - 77
    bosbouw - plantensuccessie - periodiciteit - vegetatie - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - bossen - milieubescherming - conservering - plantenecologie - nederland - forestry - plant succession - periodicity - vegetation - silviculture - forestry practices - growth - environmental factors - forests - environmental protection - conservation - plant ecology - netherlands
    Het Europese bos groeit sneller
    Nabuurs, G.J. ; Olsthoorn, A.F.M. ; Dik, E.J. - \ 1997
    Nederlands Bosbouwtijdschrift 69 (1997)1. - ISSN 0028-2057 - p. 24 - 27.
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - europa - forestry - silviculture - forestry practices - growth - environmental factors - europe
    Eind augustus '96 is in Freiburg het eindresultaat van het project 'Groeitrend in Europese bossen' gepresenteerd. Het boek is een bundeling van 22 case studies in 12 Europese landen naar de ontwikkeling van de groei in de laatste decennia
    Groeiplaatsen als basis voor bostypologie; vaste grond onder de voeten van bosbeheerders
    Wolf, R.J.A.M. ; Dort, K.W. van; Vrielink, J.G. - \ 1996
    Nederlands Bosbouwtijdschrift 68 (1996)5. - ISSN 0028-2057 - p. 177 - 189.
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - vegetatietypen - bossen - classificatie - bodemkarteringen - kaarten - nederland - forestry - silviculture - forestry practices - growth - environmental factors - vegetation types - forests - classification - soil surveys - maps - netherlands
    Fenologie en groei van bomen in relatie tot klimaatverandering
    Kramer, K. ; Mohren, G.M.J. - \ 1996
    Nederlands Bosbouwtijdschrift 68 (1996)2. - ISSN 0028-2057 - p. 73 - 78.
    bosbouw - klimaatverandering - paleoklimatologie - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - Nederland - forestry - climatic change - palaeoclimatology - silviculture - forestry practices - growth - environmental factors - Netherlands
    Onderzoek naar de groei van tamme kastanje (Castanea sativa) in Nederland
    Oosterbaan, A. - \ 1996
    Bosbouwvoorlichting 35 (1996)2. - ISSN 0166-8986 - p. 18 - 18.
    biomassa - milieufactoren - bosbouw - bosbouwkundige handelingen - groei - houtaanwas - nederland - houtteelt - opstandsontwikkeling - opstandsstructuur - bomen - castanea sativa - biomass - environmental factors - forestry - forestry practices - growth - increment - netherlands - silviculture - stand development - stand structure - trees - castanea sativa
    Samenvatting van IBN-rapport 197
    Changing forest management strategies in Sudan : a challenge for forestry educational systems
    Mahir, S.S. - \ 1996
    Agricultural University. Promotor(en): W. van den Bor; N.G. Röling. - S.l. : Mahir - ISBN 9789054854951 - 263
    bosbouw - bosbedrijfsvoering - theorie - duurzaamheid (sustainability) - opbrengsten - bosbouwkundige handelingen - sociale economie - voorlichting - onderwijs - sociale bosbouw - landgebruik - pachtstelsel - bebossing - inheemse kennis - sociale verandering - sudan - sociale processen - forestry - forest management - theory - sustainability - yields - forestry practices - socioeconomics - extension - education - social forestry - land use - tenure systems - afforestation - indigenous knowledge - social change - sudan - social processes

    This study is an effort to understand the way various categories of social actors go about their interaction with the management of forest resources in Sudan. By providing an overview and description of the motives, perceptions, and management objectives and strategies of social actors, the study tries to contribute towards better understanding of the social, economic and cultural factors influencing the resource management. The specific objectives of this study include:
    (1) Investigation of how social actors interact with forest resources in an era of rapidly changing conditions.
    (2) Get a better understanding of how changes in management objectives and strategies are influencing and are influenced by knowledge processes.
    (3) Analyze present forestry education's curriculum.
    (4) Explore possibilities of incorporating what we learn during the course of this study to propose a model for development of curriculum for forestry education in Sudan.

    This dissertation is written on the basis of empirical data collected from various individuals, groups and institutions involved in forest resources management in Sudan. The field work for the study was carried out mainly in the Central region of Sudan. However, the author's own experiences and those of other officials who worked in other locations, made the scope of the study not limited to geographical boundaries of the region.

    For the data collection, a combination of methodological instruments such as discussions, semi-structured interviews and participant observation, were used iteratively. Besides, taking a social actor as a unit of analysis, the study has used a hybrid of the systems' and the actors' perspectives as the main analytical tool.

    The main findings of this study indicate that:

    First, whereas, a forest is the unit of concern for officials, it is the tree which draws villagers' attention more than the forest as such. However, in general social actors see trees and forests as sources and signs of life. Besides, various actors attach different social, economic and/or cultural meanings to trees/forests. Consequently, they develop varying management objectives and strategies. In this regard, this study shows that similarity between foresters' and villagers' objectives is the exception rather than the rule. Foresters' management objectives are focused on management of forests for provision of forest goods and services for the nation, whereas villagers keep trees for social-cultural-spiritual-economic reasons, but rarely for firewood alone. Sometimes, what is important for villagers is seen as of 'minor importance' to foresters.

    Second, villagers traditionally, did not care about ownership of forests. However, ownership of valued-trees was well known. Notwithstanding such a situation, the government in Sudan intervened to manage the resource. Nonetheless, abolishment of the traditional Native Administrative system together with many other factors led to the situation where the state was unable to manage the resources on a sustainable basis. Hence, some of the tree/forest resources acquired the characteristics of the unowned, none-property resources.

    Third, most of the foresters see forest management mainly as consisting of a series of context-free technical activities, while villagers perform trees/forests management as part and parcel of their overall land use.

    Fourth, this study exposes social actors' appreciation concerning positive changes in each other's attitudes and behaviours and their willingness to manage forest resources jointly. Nevertheless, villagers and their leaders as well as officials have to be aware of and prepared for their new rights and responsibilities.

    Fifth, this study manifests that the formal forestry knowledge in Sudan is based on the assumption that wood is the main product. In most of their experiments forestry researchers look mainly into wood, and did not pay enough attention to non-timber- products. In addition, extension officers tend to disseminate unified, ready-made messages to various clients' segments. As well, in spite of the shown appreciation of local people's forestry knowledge, foresters rarely take villagers' observations and comments seriously.

    Sixth, women are becoming increasingly involved in forestry activities and the number of female foresters is increasing. Taking into consideration the fact that the rural Sudanese culture in many places does not allow easy interaction between male extension officers and village women, the need for female forestry extension officers seems to be well understood.

    Seventh, the following are among the learning points in relation to villagers' knowledge activities as depicted from this study:
    (1) For villagers researching and learning are inseparable. Deploying their surrounding environment in its totality, villagers carefully observe and learn experientially.
    (2) Local people's knowledge is embedded into different kinds of rituals and spiritual beliefs.
    (3) Villagers do not tend to reach to consensus and unified kind of knowledge and solutions.
    (4) Villagers normally exchange information among themselves during greetings; direct and indirect asking; certain occasions and locations such as funerals, market places and days, and religious/cultural feasts.

    Eighth, the findings of this study reveal that none of social actors alone has the technical/managerial capacity pertinent to sustainable management of forest resources. The necessary knowledge base is rather fragmented and unevenly scattered among different actors. Hence, we argued that in the absence of a suitable knowledge and information system, appropriate management of forest resources will be difficult. Forestry education has a role to play in facilitation of such knowledge and information system. Nonetheless, many economic, didactical and organizational problems remain as constraints for present institutions to perform better roles.

    Ninth, the results of this study came to support the idea that education is but one element which influences foresters' attitudes and behaviour. In reality, foresters' performance is determined by a composite of inter-related factors such as the work environment. Under the prevailing situation, learners and educators have neither enough time nor good motivation for creation of favourable learning environments.

    The main recommendations of this study are:
    (1) Foresters should take other social actors' perceptions, knowledge and management objectives into consideration when deciding about official management objectives and strategies.
    (2) Forestry educational institutions will and should have a role to play in facilitating various forest resources managers getting around a platform and discuss, learn and coordinate their resources to manage the resources on a sustainable basis. However, before being able to play such a role, they should start to see their roles as "experts' bureaux", but instead try to develop networking institutions.
    (3) Moreover, in an era of fast change, forest managers should learn more about learning. Nevertheless, to facilitate such kinds of learning, forestry educational institutions need to restructure their curricula involving other social actors and create channels for ongoing monitoring.
    (4) However, all the above mentioned requirements will be of limited effect in the absence of an overall conducive environment. Again, educators should not wait for these improvements to come, instead they should work very hard for the creation of such a conducive educational and learning environment.

    As a contribution towards development of such educational and learning environment, a model for forestry curriculum development has been proposed.

    NOPEX/Forest-Dynamo. Ground data collection and data analysis report : : fieldcampaigns in 1994 - 1995
    Oevelen, P.J. van; Woodhouse, I.H. - \ 1996
    Wageningen : Landbouwuniversiteit Wageningen (Rapport / Landbouwuniversiteit, Vakgroep Waterhuishouding 70) - 74
    remote sensing - toepassingen - bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - luchtkarteringen - zweden - remote sensing - applications - forestry - silviculture - forestry practices - growth - environmental factors - aerial surveys - sweden
    Groei en ontwikkeling van de menging Douglas-beuk; meer dan de som der delen?
    Bartelink, H.H. ; Tünnissen, A.T.F.M. - \ 1996
    Nederlands Bosbouwtijdschrift 68 (1996)1. - ISSN 0028-2057 - p. 2 - 6.
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - gemengde bossen - bomen - fagus sylvatica - pseudotsuga menziesii - gemengde opstanden - forestry - silviculture - forestry practices - growth - environmental factors - mixed forests - trees - fagus sylvatica - pseudotsuga menziesii - mixed stands
    Het nedersaksische groeiplaatsclassificatiesysteem en zijn toepasbaarheid in Nederland.
    Fanta, J. ; Kuiper, B. ; Bianchi, F.J.J.A. ; Rattink, M. - \ 1996
    Nederlands Bosbouwtijdschrift 68 (1996). - ISSN 0028-2057 - p. 168 - 170.
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - vegetatietypen - bossen - classificatie - duitsland - forestry - silviculture - forestry practices - growth - environmental factors - vegetation types - forests - classification - germany
    Phenology and growth of European trees in relation to climate change
    Kramer, K. - \ 1996
    Agricultural University. Promotor(en): J. Goudriaan; G.M.J. Mohren. - S.l. : Kramer - ISBN 9789054854647 - 210
    bosbouw - fenologie - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - klimaatverandering - paleoklimatologie - Europa - forestry - phenology - silviculture - forestry practices - growth - environmental factors - climatic change - palaeoclimatology - Europe
    Research topics

    The relationships between climate and both phenology and growth of some important European tree species were studied to evaluate the potential impacts of climate change on trees and forests in Europe. In order to make such assessments, insight is required on the mechanisms how climatic variables interact with plant processes. The topics addressed in this study were: (1) the modelling of phenology, (2) the consequences of climate change on spring frost damage, (3) the importance of phenotypic plasticity, (4) the importance of phenology on the effects of climate change on growth of monospecies deciduous forests, and (5) the importance of phenology on the effects of climate change on growth of mixed-species deciduous forests.

    Modelling phenology

    To evaluate the impacts of climate change on growth of temperate deciduous tree species, the onset and cessation of the growth must be accurately described. A review is presented on eight models predicting the date of leaf unfolding depending on temperature. These models were fitted using 57 years of observations on the date of leaf unfolding of Fagus sylvatica in The Netherlands, and used to predict 40 years of similar observations collected in Germany. As conflicting experimental evidence exist on the role of photoperiod on leaf unfolding of Fagus sylvatica, photoperiod was incorporated into each of these models.

    The timing of leaf unfolding could best be described by a model in which the effects of chilling temperatures (-5 to +10°C) and forcing temperatures (>0°C) operate sequentially in time, according to a triangular and logistic function, respectively. Including photoperiod reduced the predicting power of this model.

    Spring frost damage

    Two studies presented in literature evaluate the effect of increasing winter temperature on the probability of spring frost damage to trees. However, one study predicted an increase, while the other predicted a decrease in the probability of spring frost damage. It is unclear whether the disparity is because: (1) different models were used, (2) different climatic warming scenarios used, or (3) the tree species at the different locations respond differently to warmer winters. To evaluate the effects of climatic warming to Larix decidua, Betula pubescens, Tilia platyphylla, Fagus sylvatica, Tilia cordata, Quercus rubra, Quercus robur, Fraxinus excelcior, Quercus petraea, Picea abies and Pinussylvestris in The Netherlands and in Germany, both models were fitted to long series of observations on the date of leaf unfolding of these tree species. The impact of the two scenarios (uniformly and non-uniformly changing winter temperature) on the date of leaf unfolding and on the probability of freezing temperature around that date was evaluated. To test the importance of adaptation to local climate, hypothetical provenance transfers were analysed.

    For tree species in The Netherlands and Germany the probability of spring frost damage will decrease, provided the variability in temperature does not change. The contradictory results found in literature could be ascribed to differences among provenances adapted to their local climate, rather than to differences between either the models or the climatic warming scenarios used in these studies.


    To evaluate the potential response of individual trees to climatic warming, phenological observations of clones of Larix decidua, Betula pubescens, Tilia cordata, Populus canescens, Quercus robur, Fagus sylvatica, and Picea abies transferred over a large latitudinal range in Europe were analysed. The magnitude of the clone's response was compared to that of genetically different trees of the same species along a part of the latitudinal range, which were assumed to have adapted to their local climate.

    The responses of the date of leaf unfolding and leaf fall of the clones to temperature are similar in magnitude to those of the genetically different trees. This demonstrates that trees possess a considerable plasticity and are able to respond phenotypically to a major change in their local climate. For the clones of Larix decidua and Quercus robur the growing season may shorten with increasing temperature, because leaf fall is advanced more than leaf unfolding. In Betula pubescens and Populus canescens, leaf unfolding and leaf fall are advanced equally, whereas in Tilia cordata and Fagus sylvatica the date of leaf fall seems to be unaltered but leaf unfolding advances with increasing temperature. These differences in the duration of the growing season in response to increasing temperature may alter the competitive balance between the species in mixed stands.

    Descriptive dynamic models showed that most of the variance of the date of leaf unfolding can be accounted for by temperature. However, a generally applicable model of leaf fall based on temperature and/or photoperiod could not improve the null model, i.e. the mean date of leaf fall, because of variability in other environmental factors.

    The lowest temperature around the date of leaf unfolding and leaf fall differed among the clones. The hypothesis that the survival of the clones is curtailed by spring frosts was supported. Thus, these lowest temperatures around leaf unfolding may represent thresholds below which the species cannot survive.

    It is argued that these thresholds may be a particularly sensitive means to evaluate the impacts of climatic warming on the geographical distribution of tree species.

    Growth of monospecies forests

    The importance of three phenological types of deciduous tree for the effects of climate change on growth of monospecies forests was evaluated using the model FORGRO. The climate change scenarios used were a doubling of the C02 concentration (700 μmol mol -1) and an increase in temperature ranging from 0 to 7°C. To elucidate the relative importance of photosynthesis and allocation for this evaluation, models with different levels of mechanistic detail of photosynthesis and allocation were used. The photosynthesis approach of FORGRO was compared to the Farquhar and Von Caernmerer approach as formulated in PGEN (FORGRO-PGEN). Similarly, the allocation approach of FORGRO was compared to the transport-resistance approach, as formulated in the ITE-Edinburgh model (ITE-FORGRO). A sensitivity analysis was performed to ascertain whether the response of gross photosynthesis to a climate change scenario depends on the value assigned to parameters in these models, and to compare this sensitivity with the differences found between the phenological types. The differences in the response of annual gross photosynthesis ( Pg,a ) to the climate change scenarios between the phenological types were smaller according to ITE- FORGRO as compared to FORGRO. These differences are of a similar magnitude when comparing the two photosynthesis models. Furthermore, FORGRO-PGEN showed that the response of Pg,a to a 2 x [ 2 CO ] increases with rising temperature, thus compensating for the increase in respiration. For both FORGRO and ITEFORGRO, this C0 2 and temperature interaction was not found. Consequently, in these models the increase in respiration exceeded the increase in gross photosynthesis at the higher range of temperature rise. The sensitivity analysis showed that the models differ in the sensitivity of the response of Pg,a to a 2 x [C 2 O ] scenario combined with a temperature rise of 2°C ( C700 / T2 ), when parameter values change by ±25%. In FORGRO-PGEN, the magnitude of the response of Pg,a depended on the values of some of its parameters, especially those determining the Michaelis-Menten kinetics of Rubisco, which for these parameters exceeded the differences between the phenological types in this scenario. In both FORGRO and ITE-FORGRO, this sensitivity is similar to or less than the difference between the phenological types in the C700 / T2 scenario.

    Growth of mixed-species forests

    Using the same three phenological types and climate change scenarios, the effects of differences in phenology and spring frost damage on growth in mixed-species stands were evaluated using the models FORGRO and HYBRID. FORGRO highlights potential growth in managed forests, whereas HYBRID highlights feedbacks of carbon, water and nitrogen cycles in General Vegetation Types, based on gap model theory. Furthermore, the importance of inaccuracy of the phenological model for growth in mixed-species stands was evaluated by comparing the modelling approach with a regression approach.

    The results of the climate change scenarios indicate for both FORGRO and HYBRID that: (1) the differences in NPP of the three phenological types considered are enhanced when grown in a mixed-species stand compared to a monospecies stand; and (2) the consequences of frost damage on growth is more prominent in mixed-species stands than in monospecies stands.

    Considering the accuracy of the modelling approach compared to the regression approach for the timing of leaf unfolding and spring frost damage, the sequential model of leaf unfolding shows a similar response of the NPP as the regression approach, both for the monospecies and the mixed-species situation. The modelling approach yields, however, larger differences in the NPP between the phenological types because the model predicts a greater advancement of leaf unfolding than the regression model. Comparing the regression approach to the modelling approach for frost hardiness, the regression approach shows a greater frequency of frost damage, because according to the model, the minimum level of frost hardiness is attained after the date of leaf unfolding, thus reducing this frequency.

    The differences in phenological response to temperature can be used to evaluate the consequences of climate change on the geographical distributions of species.

    Oogsttechniek heeft grote invloed op bewaring hout voor energiedoeleinden
    Gigler, J.K. ; Bosma, A.H. - \ 1995
    Landbouwmechanisatie 46 (1995)8. - ISSN 0023-7795 - p. 16 - 17.
    energie - energiegebruik - energiebronnen - bosbouw - bosbouwtechniek - bosbouwkundige handelingen - brandhout - stapelplaats - houtkap - stamhout - natuurlijke hulpbronnen - salicaceae - opslag - bomen - nuttig gebruik - hout - arbeidskunde - energy - energy consumption - energy sources - forestry - forestry engineering - forestry practices - fuelwood - landings - logging - logs - natural resources - salicaceae - storage - trees - utilization - wood - work study
    Elektriciteit uit energiegewassen als wilg kan in de toekomst realiteit worden. Het IMAG-DLO onderzoekt of de Zweedse kennis van en ervaring met de wilgenteelt ook in Nederland past
    Ruim twintig jaar beplantingsproef Broekpolder : proefveldresultaten over de periode 1970 - 1991
    Peeters, J.P. - \ 1994
    Wageningen : IBN-DLO (IBN - rapport 107) - 155
    bosbouw - bebossing - baggerspeciedepots - industrieterreinen - mijnstort - bodemvruchtbaarheid - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - havens - bagger - stort - sediment - modder - Nederland - zuid-holland - westland - forestry - afforestation - spoil banks - industrial sites - mine spoil - soil fertility - silviculture - forestry practices - growth - environmental factors - harbours - dredgings - spoil - sediment - mud - Netherlands - zuid-holland - westland
    Growth and nutrition of Douglas fir, Scots pine and pedunculate oak in relation to soil acidification
    Visser, P.H.B. de - \ 1994
    Agricultural University. Promotor(en): N. van Breemen; G.R. Findenegg; W.G. Keltjens. - S.l. : De Visser - ISBN 9789054852902 - 185
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - bomen - bodemchemie - bodemaciditeit - verzuring - beluchting - voedingsstoffenopname (planten) - bodem ph - plantenfysiologie - neerslag - chemische eigenschappen - zuurgraad - zure regen - forestry - silviculture - forestry practices - growth - environmental factors - trees - soil chemistry - soil acidity - acidification - aeration - nutrient uptake - soil ph - plant physiology - precipitation - chemical properties - acidity - acid rain

    In a Douglas fir ( Pseudotsuga menziesii (Mirb.) Franco) and in a Scots pine ( Pinus sylvestris L.) stand on sandy soil in the Netherlands, inputs of water, nutrients and acid loads were changed for four years. Effects of soil changes on growth and nutrition were compared with similar foreign experiments, and with some soil-tree relationships in an oak ( Quercus robur L.) stand, which had different soil types within the site. Water limitations in the stands were demonstrated by a 40% to 50% increase in tree basal area growth from water additions of 3 mm d -1or more. Needle N and K contents were depressed and needle shedding was retarded in autumn by irrigation in the Douglas fir stand. In both coniferous stands mineralization and nitrate leaching were enhanced by the moister soil conditions. The modest growth response to nutrient applications in addition to irrigation, proved that no nutrient deficiencies were present at the sites, although foliar P and K increased instantly. The application of dissolved K, Mg and Ca to both acid forest soils increased Al dissolution and decreased Ca/Al ratios in soil solution. This soil reaction was even stronger when applying dissolved (NH 4 ) 2 SO 4 and was explained by the combined effect of soil exchange processes and root uptake of the applied cations, both increasing soil acidification. The applied (NH 4 ) 2 SO 4 initially enhanced tree growth, later followed by growth reduction in the forest stand and tree death in a pot trial at similar NH 4 supply rates.

    Douglas fir growth was higher at optimal water and nutrient applications when atmospheric loads were excluded. The reduced NH 4 inputs resulted in a decrease of NO 3 leaching, in a lower needle N concentration and tended to decrease Al concentrations and Al/Ca ratios in soil solution relative to the treatment with atmospheric loads.

    Transpiration of Douglas fir, as measured from sapflow, was drastically reduced during summer drought. Irrigated trees showed optimal transpiration rates and were found to absorb water more readily after rain events relative to previously water-stressed trees. NH 4 applications in a pot trial initially increased shoot growth and transpiration of juvenile Douglas fir, but strong soil acidification later impaired root functioning and water uptake.

    De bosbouw vergt een holistische benadering.
    Oldeman, R.A.A. - \ 1994
    Nederlands Bosbouwtijdschrift 66 (1994)1. - ISSN 0028-2057 - p. 13 - 19.
    conservering - bosbedrijfsvoering - bosbouw - bosbouwkundige handelingen - nederland - sociale economie - conservation - forest management - forestry - forestry practices - netherlands - socioeconomics
    Verloofing: misbruik van bossen of acceptabele bosbeheersmaatregel?
    Filius, A.M. - \ 1994
    Nederlands Bosbouwtijdschrift 66 (1994)6. - ISSN 0028-2057 - p. 226 - 234.
    bosbouw - gemengde bossen - bosbouwkundige handelingen - kosten - rentabiliteit - bosbouweconomie - bossen - bosbedrijfsvoering - nederland - gemengde opstanden - veluwe - gelderland - forestry - mixed forests - forestry practices - costs - profitability - forest economics - forests - forest management - netherlands - mixed stands - veluwe - gelderland
    Kosten per ha van omvorming van douglas naar eik/groveden en eik/groveden/Japanse lariks voor de Veluwe en kantekeningen bij het bosbeheerbeleid ten aanzien van verloofing
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