Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

Current refinement(s):

Records 1 - 20 / 42

  • help
  • print

    Print search results

  • export

    Export search results

  • alert
    We will mail you new results for this query: keywords==constraints
Check title to add to marked list
Barriers and enablers to climate change adaptation in hierarchical governance systems : the case of Vietnam
Phuong, Le Thi Hong ; Robbert Biesbroek, G. ; Wals, Arjen E.J. - \ 2018
Journal of Environmental Policy and Planning 20 (2018)4. - ISSN 1523-908X - p. 518 - 532.
adaptive capacity - climate change adaptation - constraints - enablers - hierarchical state - Social learning
Governments fulfil important roles in increasing the adaptive capacity of local communities to respond to climate change impacts, particularly in developing countries. Existing studies on how governments enable and constrain the ways in which local level communities learn and build their adaptive capacity, however, generally adopt network or market-oriented types of governance. However, the most vulnerable regions to climate change impact in the world are generally governed through hierarchical policy systems. This research aims to understand how the hierarchical policy system in Vietnam creates enables and/or constrains the policy capacity of policy actors to contribute to effective climate change adaptation. We conducted interviews (n = 26) with key actors at multiple levels of government. Our findings show the importance of clear legal institutions, available financing for implementing policies, and the training of governmental staff, particularly at district and commune levels where the policy capacities are generally too low to deal with climate change impacts. We conclude that any efforts to support local actors (i.e. smallholder farmers) should include investments in policy capacity to ensure uptake and upscaling of adaptation actions more broadly.
Sustainable growth of the Kenyan dairy sector : a quick scan of robustness, reliability and resilience
Rademaker, Corné J. ; Omedo Bebe, Bockline ; Lee, Jan van der; Kilelu, Catherine ; Tonui, Charles - \ 2016
Wageningen : Wageningen University & Research, Wageningen Livestock Research (Report 3R Kenya/WLR 979) - 66
dairy farming - dairy industry - supply chain management - governance - constraints - kenya - melkveehouderij - zuivelindustrie - ketenmanagement - beperkingen
This report provides an overview of how the Kenyan dairy sector performs in three analytical domains: the robustness of the supply chains, the reliability of institutional governance and the resilience of the innovation system. Analysis is by literature review, stakeholder interviews and a validation workshop guided by a SWOT framework to identify strengths, weaknesses, opportunities and threats. The findings inform the existing opportunities and challenges that potentially impede growth in the sector. The report is a first step towards documenting and sharing insights that support the move towards a more Robust, Reliable and Resilient (3R) dairy sector. The findings and recommendations presented will guide policy engagement and action in the transition of Dutch government bilateral engagement in Kenya from development aid–support to a trade approach in the agricultural sector, with a focus on partnering opportunities to drive competitive market-oriented dairy sector development that attracts investments.
Effects of technical interventions on flexibility of farming systems in Burkina Faso: Lessons for the design of innovations in West Africa
Andrieu, N. ; Descheemaeker, K.K.E. ; Sanou, T. ; Chia, E. - \ 2015
Agricultural Systems 136 (2015). - ISSN 0308-521X - p. 125 - 137.
crop-livestock systems - sub-saharan africa - climate-change - smallholder farmers - coping strategies - modeling approach - decision-making - constraints - uncertainty - variability
African farmers have always been exposed to climatic and economic variability and have developed a range of coping strategies. Such strategies form part of flexible farm management, an ability that may prove very valuable in the face of future climate change and market dynamics. The generally low productivity of African smallholder farming systems is usually addressed by research and development institutions by a variety of solutions for improving farm performance. However, changes to the system may affect the flexibility of farms and thus their ability to cope with variability. We quantified the added value of being flexible and how this flexibility is affected by technical changes, such as composting and cattle fattening recurrently proposed and promoted by research and development institutions and projects. The study was conducted in two villages of the agro-pastoral area of Burkina Faso, where livestock, cereals and cotton are the main farming activities. A whole-farm simulation model was developed based on information gathered during focus group meetings with farmers and detailed individual monitoring of farmers' practices. The model simulates farmers' decision rules governing the management of the cropping and livestock farm components, as well as crop and livestock production and farm gross margin. Using the existing decision rules, current farm performance was simulated by assessing the cereal balance, the fodder balance and the whole farm gross margin. Then, by comparing the mean and the coefficient of variation of these indicators resulting from (a) the existing decision rules (baseline scenario) and (b) a set of less flexible rules (rigid scenario), the added value of flexible management was revealed. The adoption of composting practices allowed a slight increase in gross margin associated with a decrease in its between-year variability in comparison with conventional practices. Cattle fattening only led to a higher gross margin in the years with high rainfall and low input prices when no management practices were used to limit dependence on external input. This kind of technical change thus requires increased management agility by farmers to deal with climatic and economic variability. We conclude that assessing the impact of technical interventions not only in terms of productivity but also in terms of changes in flexibility is useful for a better understanding of potential adoption of technical changes
Vegetable production after flooded rice improves soil properties in the Red River Delta, Vietnam
Everaarts, A.P. ; Neeteson, J.J. ; Pham Thi Thu, H. ; Struik, P.C. - \ 2015
Pedosphere 25 (2015)1. - ISSN 1002-0160 - p. 130 - 139.
sandy loam soil - physical-properties - farming systems - puddling depth - tropical asia - wheat system - constraints - opportunities - management - lowland
Vegetable production in South East Asia often is in rotation with °ooded rice. The puddling of the soil with flooded rice production may result in unfavourable soil conditions for the subsequent production of dry land crops. To establish whether permanent vegetable production results in favourable soil conditions for vegetables, the effects of five different permanent vegetable production systems and a system of vegetable production in rotation with flooded rice on soil properties after flooded rice were studied in a 2-year field experiment. Bulk density at 0.05{0.10 m depth layer decreased with permanent vegetable production and vegetable production in rotation with flooded rice. The decrease in bulk density was in°uenced by the application of organic manure and rice husks, and especially by the number of crops cultivated, suggesting that frequency of soil tillage had a major effect on bulk density. Ploughing with buffalo traction after flooded rice, in combination with construction of raised beds, could reduce or totally eliminate negative effects of puddling on soil structure. Bulk density at 0.15{0.20 m soil depth was not influenced. Soil acidity decreased significantly in all systems. Soil organic carbon increased in all systems, but significant increase was only found in two permanent vegetable production systems. Available phosphorus (P) significantly increased in two permanent vegetable production systems, with a positively correlation to the amount of P applied. The significant decrease in bulk density and increase in pH (H2O), after only 2 years, showed that soil conditions after flooded rice could be improved in a short time under intensive vegetable production.
Aboveground persistence of vascular plants in relationship to the levels of airborne nutrient deposition
Hendriks, R.J.J. ; Ozinga, W.A. ; Berg, L.J.L. van den; Noordwijk, E. ; Schaminee, J.H.J. ; Groenendael, J.M. van - \ 2014
Plant Ecology 215 (2014)11. - ISSN 1385-0237 - p. 1277 - 1286.
nitrogen deposition - constraints - impact
This paper examines whether high atmospheric nitrogen deposition affects aboveground persistence of vascular plants. We combined information on local aboveground persistence of vascular plants in 245 permanent plots in the Netherlands with estimated level of nitrogen deposition at the time of recording. Aboveground persistence of vascular plants was studied using two types of survival statistic technique: Kaplan–Meier analysis and Cox’ regression. We expected a link between nitrogen deposition and loss of plant species due to intensified herbivory or other forms of tissue loss that would lead to diminishing local aboveground persistence. This could not be detected. In contrast, a positive relation was found between local aboveground persistence of plants and high levels of ammonia deposition. This result is considered to be an indication of lower colonization access, for example due to limited space (e.g. the chance of successful establishment of individuals from new species is lower). The results are discussed in relation to the extremely high levels of nitrogen deposition in the studied plots. This study provides an indication that management practices aiming for restoration of colonization access (e.g. mowing, grazing and sod cutting) are vital under heavily eutrophied conditions.
Institutional dimensions of veterinary services reforms: responses to structural adjustment in Northern Ghana
Amankwah, K. ; Klerkx, L.W.A. ; Sakyi-Dawson, O. ; Karbo, N. ; Oosting, S.J. ; Leeuwis, C. ; Zijpp, A.J. van der - \ 2014
International Journal of Agricultural Sustainability 12 (2014)3. - ISSN 1473-5903 - p. 296 - 315.
animal health-services - developing-countries - delivery - innovation - privatization - constraints - provision - economics - systems - world
This study examines the effect of the post-1980s' structural adjustment reforms on the delivery and smallholders' use of veterinary services in two districts in Northern Ghana. Our analytical framework distinguishes between allocative, cognitive, and normative institutions to analyse the effects on four areas of service delivery: (1) prevention; (2) clinical services; (3) provision of drugs, vaccines, and other products; and (4) human health protection. The reforms were accompanied by substantial reductions in the allocation of both financial and human resources to public veterinary services; this in turn induced fragmentation in service supply, preferential service to progressive (or wealthy) farmers, and non-adherence to international protocols for livestock health reporting. A few communities self-organized to access veterinary services. Thus, the reforms triggered changes mostly in formal allocative institutions, but these triggered further changes in informal allocative, cognitive, and normative institutions that structured the impact of the reforms. The paper concludes that institutional change is not a one-off outcome of an intervention. Rather, such interventions trigger new dynamics that policy-makers and analysts need to take into account. This requires regular monitoring of anticipated and unanticipated effects of privatization and decentralization to enable policy adjustment.
PermVeg: A model to design crop sequences for permanent vegetable production systems in the Red River Delta, Vietnam
Pham Thi Thu Huong, Huong ; Everaarts, A.P. ; Berg, W. van den; Neeteson, J.J. ; Struik, P.C. - \ 2014
Journal of Agronomy and Crop Science 200 (2014)4. - ISSN 0931-2250 - p. 302 - 316.
soil - constraints - rotations - lowland
The constraints in current vegetable production systems in the Red River Delta, Vietnam, in which vegetables are rotated with flooded rice, called for the design of alternative systems of permanent vegetable production. The practical model, PermVeg, was developed to generate vegetable crop sequences for permanent vegetable production, as based on a set of rules and restrictions. Permanent vegetable production systems were designed based on the following five scenarios: (i) increased profit, (ii) reduced labour requirement, (iii) decreased costs of pesticide use, (iv) improved crop biodiversity and (v) selected crops with low-perishable products. PermVeg showed that theoretically all selected crop sequences in the different alternative systems increased farmers’ income compared to the traditional system. The system with the highest profitability increased profit per hectare per day by a factor of three as compared to the traditional system. Labour requirement in days per hectare per day in a crop sequence also increased in all systems. Except for the system with low costs of pesticide use, permanent vegetable production systems had higher pesticide costs than the traditional, vegetable – flooded rice crop sequence. Given the model outcomes, permanent vegetable production systems can be an option to improve farmers’ income, to provide labour opportunities, and, in the case of the high crop biodiversity system, to contribute to the development of sustainable production systems. The PermVeg model can act as a practical tool to rapidly explore crop sequence options and to help farmers’ decision-making.
Seasonal phenology of interactions involving short-lived annual plants, a multivoltine herbivore and its endoparasitoid wasp
Fei, M. ; Gols, R. ; Harvey, J.A. - \ 2014
Journal of Animal Ecology 83 (2014)1. - ISSN 0021-8790 - p. 234 - 244.
specialist herbivore - brassica-oleracea - trophic levels - quality - evolution - sequestration - consequences - constraints - parasitoids - coleoptera
Spatial-temporal realism is often missing in many studies of multitrophic interactions, which are conducted at a single time frame and/or involving interactions between insects with a single species of plant. In this scenario, an underlying assumption is that the host-plant species is ubiquitous throughout the season and that the insects always interact with it. We studied interactions involving three naturally occurring wild species of cruciferous plants, Brassica rapa, Sinapis arvensis and Brassica nigra, that exhibit different seasonal phenologies, and a multivoltine herbivore, the large cabbage white butterfly, Pieris brassicae, and its gregarious endoparasitoid wasp, Cotesia glomerata. The three plants have very short life cycles. In central Europe, B. rapa grows in early spring, S. arvensis in late spring and early summer, and B. nigra in mid to late summer. P. brassicae generally has three generations per year, and C. glomerata at least two. This means that different generations of the insects must find and exploit different plant species that may differ in quality and which may be found some distance from one another. Insects were either reared on each of the three plant species for three successive generations or shifted between generations from B. rapa to S. arvensis to B. nigra. Development time from neonate to pupation and pupal fresh mass were determined in P. brassicae and egg-to-adult development time and body mass in C. glomerata. Overall, herbivores performed marginally better on S. arvensis and B. nigra plants than on B. rapa plants. Parasitoids performance was closely tailored with that of the host. Irrespective as to whether the insects were shifted to a new plant in successive generations or not, development time of P. brassicae and C. glomerata decreased dramatically over time. Our results show that there were some differences in insect development on different plant species and when transferred from one species to another. However, all three plants were of generally high quality in terms of insect performance. We discuss ecological and evolutionary constraints on insects that must search in new habitats for different plant species over successive generations.
Feeling at home in public: diasporic Moroccan women negotiating leisure in Morocco and the Netherlands
Wagner, L.B. ; Peters, K.B.M. - \ 2014
Gender, Place & Culture : a Journal of Feminist Geography 21 (2014)4. - ISSN 0966-369X - p. 415 - 430.
gender - space - constraints - experience - power - city - fear
Muslim women are often cited as subject to restriction in their mobility through public space, especially in European contexts, in comparison with non-Muslim community members. Yet any woman might face restriction in her access to leisure outside the home through geographies of risk and fear, as well as geographies of care and responsibility. In this article, we describe the ways in which Moroccan Muslim women resident in Europe negotiate access to leisure outside the home, in both Europe and Morocco, demonstrating that they practice mobilities framed by safety, risk and responsibility combined with individual volition to be participants in public spaces. Using examples from interviews and ethnographic fieldwork, we discuss a notion of ‘viscosity’ as safe public space that acts as an extension of the home, where women feel comfortable enacting their daily lives and engaging in leisure practices. By comparing data from the Netherlands and Morocco, we highlight the role of Muslim-dominant and Christian-dominant public spheres in these negotiations of leisure. The ways women inhabit such spaces reflect individual concerns about personal safety, as well as maintaining respectful relations with family and being protected from unknown dangers, in ways that reflect not only religious beliefs but also geographies of risk related to other factors. Inhabiting such spaces implicates how they become part of the community at large, as visibly present participants, by negotiating many factors beyond religious beliefs as part of their access to public leisure spaces
Change and diversity in smallholder rice-fish systems: Recent evidence and policy lessons from Bangladesh
Dey, M.M. ; Spielman, D.J. ; Haque, A.B.M.M. ; Rahman, M.S. ; Valmonte-Santos, R. - \ 2013
Food Policy 43 (2013). - ISSN 0306-9192 - p. 108 - 117.
fresh-water prawn - floodplain aquaculture - southwest bangladesh - culture-systems - constraints - polyculture - fisheries - adoption - impacts - fields
Efforts to unlock the genetic potential of both rice and fish, when combined with improvements in the management of rice-fish systems, can potentially increase agricultural productivity and food security in some of the poorest and most populous countries in Asia. In Bangladesh, estimates suggest that the country's potential rice-fish production system encompasses 2-3 million hectares of land. But despite three decades of research on biophysical and technical aspects of rice-fish systems, this potential has not been fully realized due to insufficient attention given to the social, economic, and policy dimensions of rice-fish system improvement. This paper provides a characterization of the diverse and changing nature of rice-fish systems in Bangladesh to shed new light on the economic viability of different rice-fish systems and recommend policy and investment options to accelerate the development of appropriate rice-fish technologies. Data are drawn from a novel subdistrict-level survey of fishery officers, a household/enterprise survey, focus group discussions, and a meta-review of the literature on aquaculture in the country, all of which were conducted in 2010-2011. Findings indicate that concurrent rice-fish systems, alternating rice-fish systems, and collectively managed systems offer considerable potential for increasing productivity and farm incomes in Bangladesh. Findings also suggest that while innovation in these rice-fish systems is being driven by households and communities, there is need for more supportive government policies and investments to enable further innovation. Policymakers need to develop effective regulations to promote feed and fish quality and quantity, for example. More rigorous analysis of the intended and unintended impacts of these policies and investments is also necessary. (C) 2013 Elsevier Ltd. All rights reserved.
How Muslim Women in the Netherlands Negotiate Discrimination During Leisure Activities
Kloek, M.E. ; Peters, K.B.M. ; Sijtsma, M. - \ 2013
Leisure Sciences 35 (2013)5. - ISSN 0149-0400 - p. 405 - 421.
public space - urban parks - constraints - participation - recreation - race - immigration - ethnicity - americans - minority
Qualitative research about discrimination encountered by Muslim women in The Netherlands who are participating in leisure activities in public spaces shows that perceived discrimination is part of everyday life. This is especially true for women who wear the veil because their visible head covering signals their “otherness” to people. The discriminatory actions encountered by women in this sample are typically of a nonviolent nature and mostly comprise unpleasant looks and negative remarks. Perceived discrimination often does not prevent the women from participating in leisure activities. Instead, they actively negotiate discrimination by applying various coping strategies, including justification, direct confrontation, accepting the discrimination, and modifying leisure behavior.
On the nature of barriers to climate change adaptation
Biesbroek, G.R. ; Klostermann, J.E.M. ; Termeer, C.J.A.M. ; Kabat, P. - \ 2013
Regional Environmental Change 13 (2013)5. - ISSN 1436-3798 - p. 1119 - 1129.
policy success - vulnerability - framework - constraints - challenges - governance - management - risk
Considerable barriers can emerge in developing and implementing climate change adaptation strategies. Understanding the nature of barriers to adaptation is important so as to find strategic ways of dealing with them. However, our current understanding is limited and highly fragmented across the academic community. This paper aims to bring some conceptual convergence in these debates by applying a systematic review method to assess the current state of knowledge on barriers to adaptation in the peer-reviewed literature. The review results show that: (1) Barriers to adaptation have hardly been defined in the literature and no clear indicators exist so as to identify and assess them systematically. (2) An impressive number of barriers have been reported, but the list of possible barriers is seemingly endless. (3) The most frequently reported barriers relate to the institutional and social dimensions of adaptation. (4) Barriers are identified as configurations of climate and non-climate factors and conditions that emerge from the actor, the governance system, or the system of concern. (5) Barriers are mainly studied in developed countries with a strong focus on water-related domains. (6) The majority of studies on barriers use small-n inductive case approaches while comparative studies across different contexts are limited. (7) Although interventions to overcome barriers are recommended by most studies, empirical studies on interventions are scarce. We present further conceptual clarification and a more precise definition of barriers to adaptation. We conclude that future research should go beyond asking the questions ‘if’ and ‘which’ barriers to adaptation exist and begin asking ‘how’ and ‘why’ barriers emerge.
Simultaneous estimation of quantile curves using quantile sheets
Schnabel, S.K. ; Eilers, P.H.C. - \ 2013
AStA Advances in Statistical Analysis 97 (2013)1. - ISSN 1863-8171 - p. 77 - 87.
absolute deviations - regression - constraints - splines
The results of quantile smoothing often show crossing curves, in particular, for small data sets. We define a surface, called a quantile sheet, on the domain of the independent variable and the probability. Any desired quantile curve is obtained by evaluating the sheet for a fixed probability. This sheet is modeled by $P$-splines in form of tensor products of $B$-splines with difference penalties on the array of coefficients. The amount of smoothing is optimized by cross-validation. An application for reference growth curves for children is presented.
The Role of Propagule Banks from Drainage Ditches Dominated by Free-Floating or Submerged Plants in Vegetation Restoration
Zuidam, J.P. van; Raaphorst, E.P. ; Peeters, E.T.H.M. - \ 2012
Restoration Ecology 20 (2012)3. - ISSN 1061-2971 - p. 416 - 425.
sloten - waterplanten - zoetwaterecologie - plantengemeenschappen - ecologisch herstel - ditches - aquatic plants - freshwater ecology - plant communities - ecological restoration - seed bank - biodiversity - communities - sediments - constraints - macrophytes - germination - emergence - runoff - meadow
Dominance by free-floating plants results in a loss of plant species in many waters. An important source for re-establishment of non-floating aquatic plants can be the propagule bank. This study focuses on whether the propagule bank of free-floating plantdominated ditch sediments can serve as potential source for recovery of a diverse plant community. The first objective was to determine differences in propagule germination from sediments of ditches in the Netherlands that differ in vegetation composition through a seedling-emergence experiment. The second objective was to analyze the effect of sediment disturbance on the number of germinating propagules. The results show that, compared to sediments from ditches with submerged vegetation, sediments from free-floating plantdominated ditches produced significantly lower numbers of individuals and species of submerged and emergent plants, while numbers of individuals and species of free-floating plants were higher. These results suggest that sediments from free-floating plantdominated ditches have lower potential to recover a diverse plant community probably resulting from positive feedback mechanisms caused by the vegetation present, maintaining the free-floating plantdominated state. Sediment disturbance strongly favors the germination of free-floating plant propagules, especially from free-floating plantdominated ditch sediments. Ditch maintenance activities such as mowing and dredging will therefore likely favor persistence of the free-floating plantdominated state. To shift from dominance by free-floating plants to a more diverse plant community, alternative maintenance methods should be considered that cause less sediment disturbance together with measures that promote colonization such as temporary drawdown or re-introduction of species.
Effect of host-cocoon mass on adult size in the secondary hyperparasitoid wasp, Pteromalus semotus (Hymenoptera: Pteromalidae)
Harvey, J.A. ; Gumovsky, A. ; Gols, R. - \ 2012
Insect Science 19 (2012)3. - ISSN 1672-9609 - p. 383 - 390.
coccygomimus-turionellae - lysibia-nana - parasitoids - strategies - ichneumonidae - quality - fitness - larvae - constraints - growth
Parasitoids have long proven to be model organisms in studying resource-related constraints on immature development. Here we examine the relationship between host cocoon (= pupal) size in the gregarious endoparasitoid wasp, Cotesia glomerata, and development time and adult size in the solitary idiobiont hyperparasitoid, Pteromalus semotus. Little is known about the biology or ecology of this ecto-hyperparasitoid species, although it is one of the major secondary hyperparasitoids of C. glomerata. The size of the adult wasp covaried with the size of the host cocoon at parasitism. Moreover, female wasps were larger than male wasps for a given cocoon size. Adult wasps have remarkably long life-spans, 3 months on average. Longevity did not significantly differ with sex. We also examined how larvae of P. semotus exclude other potential competitors. P. semotus is protandrous, with females taking significantly longer to complete their development than males. In experiments where several eggs of P. semotus were placed on individual pupae of C. glomerata, newly hatched hyperparasitoid larvae moved rapidly over the surface of the host and destroyed the eggs of any conspecifics by biting them before they would initiate feeding on host tissues. Our results are discussed in relation to those with other studies with solitary ichneumonid idiobiont hyperparasitoids of C. glomerata.
Development of a hyperparasitoid wasp in different stages of its primary parasitoid and secondary herbivore hosts
Harvey, J.A. ; Gols, R. ; Vet, L.E.M. ; Kruidhof, H.M. - \ 2012
Journal of Insect Physiology 58 (2012)11. - ISSN 0022-1910 - p. 1463 - 1468.
sex-ratio - heliothis-virescens - nutritional ecology - size - fitness - hymenoptera - growth - quality - constraints - suitability
Parasitoid wasps are model organisms for exploring constraints on life history and development strategies in arthropods. Koinobiont parasitoids attack hosts that may vary considerably in size at parasitation. Thus far, studies exploring koinobiont development in hosts of different size have been exclusively done with primary parasitoids attacking insect herbivores. However, the larvae of primary koinobiont parasitoids may in turn be attacked by koinobiont hyperparasitoids. We examined development of the gregarious hyperparasitoid Baryscapus galactopus in different stages of its primary parasitoid host, Cotesia glomerata, itself developing in different stages of caterpillars of the cabbage butterfly, Pieris brassicae. This is the first study exploring hyperparasitoid development in different stages of a primary and secondary host. Second instar (L2) larvae of P. brassicae were parasitized by C. glomerata, and separate cohorts of L3 to L5 P. brassicae containing different stages of C. glomerata were then presented to B. galactopus females. B. galactopus was able to parasitize tiny larvae of C. glomerata in L3 caterpillars of P. brassicae, but hyperparasitism efficiency increased in later instars of both C. glomerata and P. brassicae. Development time of B. galactopus was extended in younger C. glomerata/P. brassicae hosts, whereas adult mass was largest when C. glomerata was attacked in L3 through early L5 P. brassicae. Our results show that B. galactopus adjusts its development rate in accordance with the size of both its primary and secondary hosts, in order to ensure survival. Adaptive responses to phylogenetic constraints on the development of primary hyperparasitoids are discussed.
Architecture of Iberian canopy tree species in relation to wood density, shade tolerance and climate
Poorter, L. ; Lianes, E. ; Moreno-de las Heras, M. ; Zavala, M.A. - \ 2012
Plant Ecology 213 (2012)5. - ISSN 1385-0237 - p. 707 - 722.
life-history variation - tropical trees - trade-offs - panamanian forest - allometry - traits - growth - differentiation - constraints - performance
Tree architecture has important consequences for tree performance as it determines resource capture, mechanical stability and dominance over competitors. We analyzed architectural relationships between stem and crown dimensions for 13 dominant Iberian canopy tree species belonging to the Pinaceae (six Pinus species) and Fagaceae (six Quercus species and Fagus sylvatica) and related these architectural traits to wood density, shade tolerance and climatic factors. Fagaceae had, compared with Pinaceae, denser wood, saplings with wider crowns and adults with larger maximal crown size but smaller maximal height. In combination, these traits enhance light acquisition and persistence in shaded environments; thus, contributing to their shade tolerance. Pinaceae species, in contrast, had low-density wood, allocate more resources to the formation of the central trunk rather than to branches and attained taller maximal heights, allowing them to grow rapidly in height and compete for light following disturbances; thus, contributing to their high light requirements. Wood density had a strong relationship with tree architecture, with dense-wooded species having smaller maximum height and wider crowns, probably because of cheaper expansion costs for producing biomechanically stable branches. Species from arid environments had shorter stems and shallower crowns for a given stem diameter, probably to reduce hydraulic path length and assure water transport. Wood density is an important correlate of variation in tree architecture between species and the two dominant families, with potentially large implications for their resource foraging strategies and successional dynamics.
The seasonal cycle amplitude of total column CO2: Factors behind the model-observation mismatch
Basu, S. ; Houweling, S. ; Peters, W. ; Sweeney, C. ; Machida, T. ; Maksyutov, S. - \ 2011
Journal of Geophysical Research: Atmospheres 116 (2011)D23. - ISSN 2169-897X - 14 p.
carbon-dioxide exchange - in-situ observations - atmospheric co2 - lower stratosphere - transport - inversion - sinks - constraints - calibration - delta-c-13
CO2 surface fluxes that are statistically consistent with surface layer measurements of CO2, when propagated forward in time by atmospheric transport models, underestimate the seasonal cycle amplitude of total column CO2 in the Northern temperate latitudes by 1-2 ppm (Yang et al, 2007). In this manuscript we verify the systematic nature of this underestimation at a number of TCCON stations by comparing their measurements with a number of transport models. In particular, at Park Falls, Wisconsin (USA) we estimate this mismatch to be 1.4 ppm, and try to attribute portions of this mismatch to different factors affecting the total column. We find that errors due to the averaging kernel and prior used in forward models, water vapor in the model atmosphere, incorrect vertical transport by transport models in the free troposphere, incorrect aging of air in transport models in the stratosphere, and airmass dependence in TCCON data can explain up to 1 ppm of this mismatch. The remaining 0.4 ppm mismatch is at the edge of the accuracy requirement on satellite measurements to improve on our current estimate of surface fluxes. Uncertainties in the biosphere fluxes driving the transport models could explain a part of the remaining mismatch, implying that with corrections to the factors behind the accounted-for 1 ppm underestimation, present inverse modeling frameworks could effectively assimilate satellite CO2 measurements.
International diversification and Microfinance
Galema, R. ; Lensink, B.W. ; Spierdijk, L. - \ 2011
Journal of International Money and Finance 30 (2011)3. - ISSN 0261-5606 - p. 507 - 515.
constraints - markets
International commercial banks, institutional investors, and private investors have become increasingly interested in financing microfinance institutions (MFIs). This paper investigates whether adding microfinance funds to a portfolio of risky international assets yields diversification gains. By using mean-variance spanning tests with short-sale constraints, we find that investing in microfinance may be attractive for investors seeking a better risk–return profile. Specifically, the analysis suggests that investing in MFIs from Latin America, or microfinance and rural banks yields more efficient portfolios. In contrast, adding MFIs from Africa or microfinance NGOs to a portfolio of international assets is not beneficial for a mean-variance investor.
Enhancement of Late Successional Plants on Ex-Arable Land by Soil Inoculations
Carbajo, V. ; Braber, B. den; Putten, W.H. van der; Deyn, G.B. de - \ 2011
PLoS One 6 (2011)7. - ISSN 1932-6203
species-rich grassland - restoration ecology - mycorrhizal fungi - communities - diversity - fertility - chronosequence - agriculture - constraints - reduction
Restoration of species-rich grasslands on ex-arable land can help the conservation of biodiversity but faces three big challenges: absence of target plant propagules, high residual soil fertility and restoration of soil communities. Seed additions and top soil removal can solve some of these constraints, but restoring beneficial biotic soil conditions remains a challenge. Here we test the hypotheses that inoculation of soil from late secondary succession grasslands in arable receptor soil enhances performance of late successional plants, especially after top soil removal but pending on the added dose. To test this we grew mixtures of late successional plants in arable top (organic) soil or in underlying mineral soil mixed with donor soil in small or large proportions. Donor soils were collected from different grasslands that had been under restoration for 5 to 41 years, or from semi-natural grassland that has not been used intensively. Donor soil addition, especially when collected from older restoration sites, increased plant community biomass without altering its evenness. In contrast, addition of soil from semi-natural grassland promoted plant community evenness, and hence its diversity, but reduced community biomass. Effects of donor soil additions were stronger in mineral than in organic soil and larger with bigger proportions added. The variation in plant community composition was explained best by the abundances of nematodes, ergosterol concentration and soil pH. We show that in controlled conditions inoculation of soil from secondary succession grassland into ex-arable land can strongly promote target plant species, and that the role of soil biota in promoting target plant species is greatest when added after top soil removal. Together our results point out that transplantation of later secondary succession soil can promote grassland restoration on ex-arable land.
Check title to add to marked list
<< previous | next >>

Show 20 50 100 records per page

Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.