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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Biodiversity-ecosystem functioning relationships in a long-term non-weeded field experiment
Veen, G.F. ; Putten, Wim H. van der; Bezemer, T.M. - \ 2018
Ecology 99 (2018)8. - ISSN 0012-9658 - p. 1836 - 1846.
diversity–productivity - diversity–stability - ecosystem functioning - functional divergence - functional richness - grassland - long-term - species diversity

Many grassland biodiversity experiments show a positive relationship between biodiversity and ecosystem functioning, however, in most of these experiments plant communities are established by sowing and natural colonization is prevented by selective weeding of non-sown species. During ecosystem restoration, for example on abandoned fields, plant communities start on bare soil, and diversity is often manipulated in a single sowing event. How such initial plant diversity manipulations influence plant biodiversity development and ecosystem functioning is not well understood. We examined how relationships between taxonomic and functional diversity, biomass production and stability develop over 16 yr in non-weeded plots sown with 15 species, four species, or that were not sown. We found that sown plant communities become functionally similar to unsown, naturally colonized plant communities. However, initial sowing treatments had long-lasting effects on species composition and taxonomic diversity. We found only few relationships between biomass production, or stability in biomass production, and functional or taxonomic diversity, and the ones we observed were negative. In addition, the cover of dominant plant species was positively related to biomass production and stability. We conclude that effects of introducing plant species at the start of secondary succession can persist for a long time, and that in secondary succession communities with natural plant species dynamics diversity–functioning relationships can be weak or negative. Moreover, our findings indicate that in systems where natural colonization of species is allowed effects of plant dominance may underlie diversity–functioning relationships.

Can root trait diversity explain complementarity effects in a grassland biodiversity experiment?
Bakker, Lisette M. ; Mommer, Liesje ; Ruijven, Jasper Van - \ 2018
Journal of Plant Ecology 11 (2018)1. - ISSN 1752-9921 - p. 73 - 84.
biodiversity effects - functional diversity - grassland - resource complementarity - roots - trait diversity
Aims The positive relationship between plant biodiversity and community productivity is well established. However, our knowledge about the mechanisms underlying these positive biodiversity effects is still limited. One of the main hypotheses is that complementarity in resource uptake is responsible for the positive biodiversity effects: plant species differ in resource uptake strategy, which results in a more complete exploitation of the available resources in space and time when plant species are growing together. Recent studies suggest that functional diversity of the community, i.e. the diversity in functional characteristics ('traits') among species, rather than species richness per se, is important for positive biodiversity effects. However, experimental evidence for specific trait combinations underlying resource complementarity is scarce. As the root system is responsible for the uptake of nutrients and water, we hypothesize that diversity in root traits may underlie complementary resource use and contribute to the biodiversity effects. Methods In a common garden experiment, 16 grassland species were grown in monoculture, 4-species mixtures differing in root trait diversity and 16-species mixtures. The 4-species mixtures were designed to cover a gradient in average rooting depth. Above-ground biomass was cut after one growing season and used as a proxy for plant productivity to calculate biodiversity effects. Important Findings Overall, plant mixtures showed a significant increase in biomass and complementarity effects, but this varied greatly between communities. However, diversity in root traits (measured in a separate greenhouse experiment and based on literature) could not explain this variation in complementarity effects. Instead, complementarity effects were strongly affected by the presence and competitive interactions of two particular species. The large variation in complementarity effects and significant effect of two species emphasizes the importance of community composition for positive biodiversity effects. Future research should focus on identifying the traits associated with the key role of particular species for complementarity effects. This may increase our understanding of the links between functional trait composition and biodiversity effects as well as the relative importance of resource complementarity and other underlying mechanisms for the positive biodiversity effects.
Nitrogen Fertilizer Replacement Value of Concentrated Liquid Fraction of Separated Pig Slurry Applied to Grassland
Middelkoop, J.C. Van; Holshof, G. - \ 2017
Communications in Soil Science and Plant Analysis 48 (2017)10. - ISSN 0010-3624 - p. 1132 - 1144.
Fertilizer replacement value - grassland - mineral concentrate - nitrogen
Seven grassland experiments on sandy and clay soils were performed during a period of 4 years to estimate the nitrogen (N) fertilizer replacement value (NFRV) of concentrated liquid fractions of separated pig slurry (mineral concentrate: MC). The risk of nitrate leaching when applying MC was compared to when applying mineral fertilizers. Grassland yields in 2009–2012 fertilized with MC were compared with grassland fertilized with two mineral fertilizers: granulated calcium ammonium nitrate and liquid ammonium nitrate (LAN). The mineral fertilizers comprised 50% nitrate-N and 50% ammonium-N, and MC comprised 95–100% ammonium-N. Treatment application rates included zero N and three incremental rates of N fertilization. The liquid fertilizers were shallow injected (0–5 cm). The NFRV of MCs was 75% on sandy and 58% on clay soil with granulated ammonium nitrate as reference, and 89% on sandy and 92% on clay soil with LAN as reference. Risk of nitrate leaching after application of MC, measured in residual soil mineral N post-growing season and N in the upper groundwater in the following spring, was equal to that for mineral fertilizers.
Changes in soil phosphorus pools of grasslands following 17 yrs of balanced application of manure and fertilizer
Salm, C. van der; Middelkoop, J.C. van; Ehlert, P.A.I. - \ 2017
Soil Use and Management 33 (2017)1. - ISSN 0266-0032 - p. 2 - 12.
balanced fertilizer application - grassland - long-term experiments - soil P balance - Soil test P

Limiting the use of phosphorous (P) in intensive agriculture is necessary to decrease losses to surface waters. Balanced fertilizer application (P supply equals P offtake by the crop) is a first step to limit the use of P. However, it is questioned whether this balance approach is sufficient to maintain soil fertility. A long-term field experiment (17 yr), on grazed grassland, has been conducted on sandy soil, marine clay soil and peat soil to obtain insight into the effects of balanced P fertilizer application on soil test P values and to explain the results by changes in P pools in the soil. The balance approach led to a gradual decline in plant available P, measured as P-AL, in the topsoil (<0.10 m deep). This decline was accompanied by a decline in oxalate extractable P, dithionite extractable P and inorganic P (0.5 m H2SO4). The decline in these mineral P pools in the topsoil was (partly) compensated by an increase in the amount of organic P. There was evidence for the accumulation of P in an occluded form, especially at one of sites which received P as Gafsa rock phosphate [Ca3(PO4)2].

To Tree or Not to Tree : Cultural Views from Ancient Romans to Modern Ecologists
Holmgren, Milena ; Scheffer, Marten - \ 2017
Ecosystems 20 (2017)1. - ISSN 1432-9840 - p. 62 - 68.
ecosystem services - forest - grassland - land degradation - savanna - tree encroachment - visions of nature

Few things are more defining in a landscape compared to the absence or presence of trees, both in aesthetic and in functional terms. At the same time, tree cover has been profoundly affected by humans since ancient times. It is therefore not surprising that opinions about deforestation and colonization of landscapes by trees have always been strong. Although loss of forests is often lamented, there is also profound cultural affection for open landscapes including some that have been deforested in the past. Here we take a historical view on perceptions of changing tree cover, and subsequently argue that the current ecological literature on forest-savanna-grassland transitions is not immune to value-laden perspectives. So far, ecosystem science has not done enough to analyze the effects of tree cover changes on ecosystem services and indicators of human well-being. Until these analyses are done, debates about forested versus open landscapes will be clashes of values rather than scientific evaluations. We discuss how ecosystem science may contribute to developing this field.

Farmland biodiversity and agricultural management on 237 farms in 13 European and two African regions
Lüscher, G. ; Ammari, Y. ; Andriets, A. ; Angelova, Siyka ; Arndorfer, Michaela ; Bailey, D. ; Balázs, K. ; Bogers, M.M.B. ; Bunce, R.G.H. ; Choisis, Jean Philippe ; Dennis, P. ; Díaz, M. ; Dyman, T. ; Eiter, Sebastian ; Fjellstad, W. ; Fraser, M. ; Friedel, Jürgen K. ; Garchi, S. ; Geijzendorffer, I.R. ; Gomiero, Tiziano ; González-Bornay, G. ; Guteva, Y. ; Herzog, F. ; Jeanneret, P. ; Jongman, R.H.G. - \ 2016
agricultural management - arable crop - bee - BioBio - earthworm - grassland - habitat diversity - permanent crop - spider - Tunesia - Uganda - vascular plant
Farmland is a major land cover type in Europe and Africa and provides habitat for numerous species. The severe decline in farmland biodiversity of the last decades has been attributed to changes in farming practices, and organic and low-input farming are assumed to mitigate detrimental effects of agricultural intensification on biodiversity. Since the farm enterprise is the primary unit of agricultural decision making, management-related effects at the field scale need to be assessed at the farm level. Therefore, in this study, data were collected on habitat characteristics, vascular plant, earthworm, spider, and bee communities and on the corresponding agricultural management in 237 farms in 13 European and two African regions. In 15 environmental and agricultural homogeneous regions, 6–20 farms with the same farm type (e.g., arable crops, grassland, or specific permanent crops) were selected. If available, an equal number of organic and non-organic farms were randomly selected. Alternatively, farms were sampled along a gradient of management intensity. For all selected farms, the entire farmed area was mapped, which resulted in total in the mapping of 11 338 units attributed to 194 standardized habitat types, provided together with additional descriptors. On each farm, one site per available habitat type was randomly selected for species diversity investigations. Species were sampled on 2115 sites and identified to the species level by expert taxonomists. Species lists and abundance estimates are provided for each site and sampling date (one date for plants and earthworms, three dates for spiders and bees). In addition, farmers provided information about their management practices in face-to-face interviews following a standardized questionnaire. Farm management indicators for each farm are available (e.g., nitrogen input, pesticide applications, or energy input). Analyses revealed a positive effect of unproductive areas and a negative effect of intensive management on biodiversity. Communities of the four taxonomic groups strongly differed in their response to habitat characteristics, agricultural management, and regional circumstances. The data has potential for further insights into interactions of farmland biodiversity and agricultural management at site, farm, and regional scale.
Variation in elevation and sward height facilitate coexistence of goose species through allometric responses in wetlands
Zhang, Yong ; Prins, Herbert H.T. ; Cao, Lei ; Zhao, Meijuan ; Boer, Fred de - \ 2016
Waterbirds 39 (2016)1. - ISSN 1524-4695 - p. 34 - 44.
Anser albifrons - Anser fabalis - Bean Goose - body size - forage quality - forage quantity - grassland - Greater White-fronted Goose - habitat selection - heterogeneity

Allometric scaling law predicts that herbivores respond differently to the availability of resources, mediated by body size. However, studies of allometric responses have often focused on animals with a relatively large difference in body size. Here, using a correlative field study, habitat use by two herbivorous species, the Bean Goose (Anser fabalis) and the Greater White-fronted Goose (A. albifrons), with a relatively small difference in body size was investigated during the wintering period. Both a generalized linear mixed model and a mixed logistic regression model showed that both species selected lower lying areas that were recently exposed, and, as expected, the smaller Greater White-fronted Goose showed a stronger selection of foraging habitat than the larger Bean Goose. Sward height also influenced habitat selection by both species, and the smaller species selected shorter swards than the larger species. In terms of forage quality, both models failed to detect a significant effect of nitrogen content on goose habitat selection. A logistic regression model showed that structural heterogeneity of the sward negatively correlated with the patch selection of the smaller species, but for the larger species such a correlation was not found. In agreement with our hypotheses, our results provide some preliminary indication that coexistence of the two goose species studied here might be mediated by an allometric response even if the difference in body size is relatively small.

Spatial heterogeneity of plant–soil feedback affects root interactions and interspecific competition
Hendriks, M. ; Ravenek, J. ; Smit-Tiekstra, A.E. ; Paauw, J.W.M. van der; Caluwe, H. de; Putten, W.H. van der; Kroon, H. de; Mommer, L. - \ 2015
New Phytologist 207 (2015)3. - ISSN 0028-646X - p. 830 - 840.
nutrient heterogeneity - species-diversity - population-dynamics - relative abundance - deciduous woodland - temporal variation - borne pathogens - grassland - community - coexistence
Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands.
Defoliation and soil compaction jointly drive large-herbivore grazing effects on plants and soil arthropods on clay soil
Klink, R. van; Schrama, M. ; Nolte, S. ; Bakker, J.P. ; Wallis de Vries, M.F. ; Berg, M.P. - \ 2015
Ecosystems 18 (2015)4. - ISSN 1432-9840 - p. 671 - 685.
salt-marsh - nitrogen mineralization - wadden sea - mountain pastures - grassland - collembola - management - diversity - growth - cow
In addition to the well-studied impacts of defecation and defoliation, large herbivores also affect plant and arthropod communities through trampling, and the associated soil compaction. Soil compaction can be expected to be particularly important on wet, fine-textured soils. Therefore, we established a full factorial experiment of defoliation (monthly mowing) and soil compaction (using a rammer, annually) on a clay-rich salt marsh at the Dutch coast, aiming to disentangle the importance of these two factors. Additionally, we compared the effects on soil physical properties, plants, and arthropods to those at a nearby cattle-grazed marsh under dry and under waterlogged conditions. Soil physical conditions of the compacted plots were similar to the conditions at cattle-grazed plots, showing decreased soil aeration and increased waterlogging. Soil salinity was doubled by defoliation and quadrupled by combined defoliation and compaction. Cover of the dominant tall grass Elytrigia atherica was decreased by 80% in the defoliated plots, but cover of halophytes only increased under combined defoliation and compaction. Effects on soil micro-arthropods were most severe under waterlogging, showing a fourfold decrease in abundance and a smaller mean body size under compaction. Although the combined treatment of defoliation and trampling indeed proved most similar to the grazed marsh, large discrepancies remained for both plant and soil fauna communities, presumably because of colonization time lags. We conclude that soil compaction and defoliation differently affect plant and arthropod communities in grazed ecosystems, and that the magnitude of their effects depends on herbivore density, productivity, and soil physical properties.
A novel protocol for assessment of aboveground biomass in rangeland environments
Mundava, C. ; Schut, A.G.T. ; Helmholtz, P. ; Stovold, R.G.H. ; Donald, G. ; Lamb, D.W. - \ 2015
The Rangeland Journal 37 (2015)2. - ISSN 1036-9872 - p. 157 - 167.
rising-plate-meter - dry tropical savanna - standing crop - herbage mass - grazing strategies - pasture biomass - vegetation - grassland - yield - management
Current methods to measure aboveground biomass (AGB) do not deliver adequate results in relation to the extent and spatial variability that characterise rangelands. An optimised protocol for the assessment ofAGBis presented that enables calibration and validation of remote-sensing imagery or plant growth models at suitable scales. The protocol combines a limited number of destructive samples with non-destructive measurements including normalised difference vegetation index (NDVI), canopy height and visual scores of AGB. A total of 19 sites were sampled four times during two growing seasons. Fresh and dry matter weights of dead and green components ofAGBwere recorded. Similarity of responses allowed grouping into Open plains sites dominated by annual grasses, Bunch grass sites dominated by perennial grasses and Spinifex (Triodia spp.) sites. Relationships between non-destructive measurements and AGB were evaluated with a simple linear regression per vegetation type. Multiple regression models were first used to identify outliers and then cross-validated using a 'Leave-One-Out' and 'Leave-Site-Out' (LSO) approach on datasets including and excluding the identified outliers. Combining all non-destructive measurements into one single regression model per vegetation type provided strong relationships for all seasons for total and green AGB (adjusted R2 values of 0.65-0.90) for datasets excluding outliers. The model provided accurate assessments of total AGB in heterogeneous environments for Bunch grass and Spinifex sites (LSO-Q2 values of 0.70-0.88), whereas assessment of green AGB was accurate for all vegetation types (LSO-Q2 values of 0.62-0.84). The protocol described can be applied at a range of scales while considerably reducing sampling time
Ecological contrasts drive responses of wintering farmland birds to conservation management
Hammers, M. ; Muskens, G.J.D.M. ; Kats, R.J.M. van; Teunissen, W.A. ; Kleijn, D. - \ 2015
Ecography 38 (2015)8. - ISSN 0906-7590 - p. 813 - 821.
agri-environment schemes - agricultural intensification - biodiversity - populations - grassland - food - metaanalysis - communities - diversity - declines
In the past decades, large-scale conservation programs have been implemented to halt the decline of farmland species. The mechanisms explaining the effectiveness of these programs remain poorly understood. Here we test the recent hypothesis that the effects of conservation management are determined by the ecological contrasts in limiting resources they create relative to the baseline situation. We examine responses of wintering seed-eating farmland birds to the experimental establishment of winter food plots in areas with contrasting food availability. We found that farmland bird abundance and species richness were strongly positively related to seed availability, regardless of compositional differences between agricultural landscapes. In line with the ecological contrast hypothesis, the responses of wintering farmland birds increased with increasing conservation induced contrast in a key limiting resource. Both contrasts and relative responses were negatively related to baseline food availability, but the absolute bird density in food plots was unrelated to baseline food availability. This indicates that both relative and absolute effects of conservation management need to be considered to properly evaluate the effectiveness of conservation management.
Plant functional types define magnitude of drought response in peatland CO2 exchange
Kuiper, J.J. ; Mooij, W.M. ; Bragazza, L. ; Robroek, B.J.M. - \ 2014
Ecology 95 (2014)1. - ISSN 0012-9658 - p. 123 - 131.
sphagnum mosses - nitrogen availability - removal experiment - species-diversity - moisture controls - water-content - carbon - ecosystems - grassland - bog
Peatlands are important sinks for atmospheric carbon (C), yet the role of plant functional types (PFTs) for C sequestration under climatic perturbations is still unclear. A plant-removal experiment was used to study the importance of vascular PFTs for the net ecosystem CO2 exchange (NEE) during (i.e., resistance) and after (i.e., recovery) an experimental drought. The removal of PFTs caused a decrease of NEE, but the rate differed between microhabitats (i.e., hummocks and lawns) and the type of PFTs. Ericoid removal had a large effect on NEE in hummocks, while the graminoids played a major role in the lawns. The removal of PFTs did not affect the resistance or the recovery after the experimental drought. We argue that the response of Sphagnum mosses (the only PFT present in all treatments) to drought is dominant over that of coexisting PFTs. However, we observed that the moment in time when the system switched from C sink to C source during the drought was controlled by the vascular PFTs. In the light of climate change, the shifts in species composition or even the loss of certain PFTs are expected to strongly affect the future C dynamics in response to environmental stress.
Grazing-induced changes in plant–soil feedback alter plant biomass allocation
Veen, C.F. ; Vries, S. de; Bakker, E.S. ; Putten, W.H. van der; Olff, H. - \ 2014
Oikos 123 (2014)7. - ISSN 0030-1299 - p. 800 - 806.
tallgrass prairie - borne pathogens - invasive plant - grassland - herbivores - community - competition - coexistence - defoliation - diversity
Large vertebrate herbivores, as well as plant–soil feedback interactions are important drivers of plant performance, plant community composition and vegetation dynamics in terrestrial ecosystems. However, it is poorly understood whether and how large vertebrate herbivores and plant–soil feedback effects interact. Here, we study the response of grassland plant species to grazing-induced legacy effects in the soil and we explore whether these plant responses can help us to understand long-term vegetation dynamics in the field. In a greenhouse experiment we tested the response of four grassland plant species, Agrostis capillaris, Festuca rubra, Holcus lanatus and Rumex acetosa, to field-conditioned soils from grazed and ungrazed grassland. We relate these responses to long-term vegetation data from a grassland exclosure experiment in the field. In the greenhouse experiment, we found that total biomass production and biomass allocation to roots was higher in soils from grazed than from ungrazed plots. There were only few relationships between plant production in the greenhouse and the abundance of conspecifics in the field. Spatiotemporal patterns in plant community composition were more stable in grazed than ungrazed grassland plots, but were not related to plant–soil feedbacks effects and biomass allocation patterns. We conclude that grazing-induced soil legacy effects mainly influenced plant biomass allocation patterns, but could not explain altered vegetation dynamics in grazed grasslands. Consequently, the direct effects of grazing on plant community composition (e.g. through modifying light competition or differences in grazing tolerance) appear to overrule indirect effects through changes in plant–soil feedback.
The effectiveness of ditch banks as dispersal corridor for plants in agricultural landscapes depends on species' dispersal traits
Dijk, W.F.A. van; Ruijven, J. van; Berendse, F. ; Snoo, G.R. de - \ 2014
Biological Conservation 171 (2014). - ISSN 0006-3207 - p. 91 - 98.
agri-environment schemes - european countries - biodiversity - grassland - farmland - habitat - colonization - fragmentation - connectivity - pollinators
The effectiveness of agri-environment schemes (AES) in enhancing biodiversity in agricultural landscapes is still strongly debated. In the Netherlands, one of the most widely implemented AES is the management of ditch banks to enhance plant species diversity. Previous research has shown that this type of AES has not led to increases in plant diversity. However, this work also showed that the success of this type of AES may depend on the presence of source populations in the surrounding areas. In this study we investigated if species-rich nature reserves can act as seed sources for agricultural ditch banks under AES and whether this function of nature reserves differs among plant species with different dispersal capacities. We used data collected by farmers over a 10 year period to analyse trends in species richness of target plants and in different dispersal groups in ditch banks under AES at different distances from nature reserves. Our results demonstrate that nature reserves can act as species rich sources in agricultural landscapes and that adjacent AES ditch banks can facilitate the colonisation of the surrounding agricultural landscape. However, the suitability of ditch banks as corridors depends on the dispersal capacity of a species. Particularly water-dispersed species clearly spread from nature reserves into the surrounding agricultural landscape along ditches. In contrast, species without adaptations to disperse over long distances do not show these spatiotemporal patterns.
Effects of large herbivores on wood pasture dynamics in a European wetland system
Cornelissen, P. ; Bokdam, J. ; Sykora, K.V. ; Berendse, F. - \ 2014
Basic and Applied Ecology 15 (2014)5. - ISSN 1439-1791 - p. 396 - 406.
sambucus-nigra l - associational susceptibility - red deer - vegetation - facilitation - mosaics - grassland - neighbors - patterns - litter
Whether self-regulating large herbivores play a key role in the development of wood-pasture landscapes remains a crucial unanswered question for both ecological theory and nature conservation. We describe and analyse how a ‘partly self-regulating’ population of cattle, horses and red deer affected the development of the woody vegetation in the Oostvaardersplassen nature reserve (Netherlands). Using aerial photographs from 1980 to 2011, we analysed the development of shrubs and trees. Before the large herbivores were introduced in the Oostvaardersplassen in 1983, the woody vegetation increased and vegetation type significantly affected the number of establishments. Cover of woody species increased further from 1983 to 1996, not only by canopy expansion but also by new establishments. After 1996, cover of the woody vegetation decreased from 30% to
Socio-Cultural and Economic Valuation of Ecosystem Services Provided by Mediterranean Mountain Agroecosystems
Bernues, A. ; Rodriguez-Ortega, T. ; Ripoll Bosch, R. ; Alfnes, F. - \ 2014
PLoS ONE 9 (2014)7. - ISSN 1932-6203
farming systems - natural park - trade-offs - conservation - landscape - europe - biodiversity - preferences - grassland - framework
The aim of this work was to elucidate the socio-cultural and economic value of a number of ecosystem services delivered by mountain agroecosystems (mostly grazing systems) in Euro-Mediterranean regions. We combined deliberative (focus groups) and survey-based stated-preference methods (choice modelling) to, first, identify the perceptions of farmers and other citizens on the most important ecosystem services and, second, to value these in economic terms according to the willingness to pay of the local (residents of the study area) and general (region where the study area is located) populations. Cultural services (particularly the aesthetic and recreational values of the landscape), supporting services (biodiversity maintenance) and some regulating services (particularly fire risk prevention) were clearly recognized by both farmers and citizens, with different degrees of importance according to their particular interests and objectives. The prevention of forest fires (
Ungulate herbivory overrides rainfall impacts on herbaceous regrouth and residual biomass in a key resource area
Muthoni, F.K. ; Groen, T.A. ; Skidmore, A.K. ; Oel, P.R. van - \ 2014
Journal of Arid Environments 100-101 (2014). - ISSN 0140-1963 - p. 9 - 17.
net primary productivity - papyrus cyperus-papyrus - lake naivasha - nonequilibrium concepts - semiarid savanna - kenya - vegetation - grassland - ecosystem - plants
Key grazing lands that provide dry season forage to both resident and migrating ungulates may experience heavy grazing impacts during the dry season, thereby jeopardizing future forage productivity. In this study a herbivore exclosure experiment was used to quantify the effects of grazing by large ungulates on herbaceous regrowth and residual aboveground biomass in a fragmented key resource area; the fringe zone around Lake Naivasha, Kenya. Top-down control mechanisms were prevalent in both the dry and wet seasons suggesting the existence of a high resident herbivore density. Intense grazing significantly reduced residual biomass that in turn reduced plant regrowth. An increased frequency of defoliation reduced regrowth during the dry season demonstrating the negative effect resulting from high herbivore densities during the dry season. This study indicates that grazing exerts a higher control on regrowth than rainfall as heavily grazed residual biomass did not recover during the following wet season.
Liebig's law of the minimum applied to a greenhouse gas: Alleviation of P-limitation reduces soil N2O emmission
Baral, B.R. ; Kuyper, T.W. ; Groenigen, J.W. van - \ 2014
Plant and Soil 374 (2014)1-2. - ISSN 0032-079X - p. 539 - 548.
nitrous-oxide emission - agricultural soils - phosphorus - fertilizer - denitrification - mineralization - mycorrhizas - netherlands - grassland - release
Emission of the greenhouse gas (GHG) nitrous oxide (N2O) are strongly affected by nitrogen (N) fertilizer application rates. However, the role of other nutrients through stoichiometric relations with N has hardly been studied. We tested whether phosphorus (P) availability affects N2O emission. We hypothesized that alleviation of plant P-limitation reduces N2O emission through lowering soil mineral N concentrations. We tested our hypothesis in a pot experiment with maize (Zea mays L.) growing on a P-limiting soil/sand mixture. Treatment factors included P and N fertilization and inoculation with Arbuscular Mycorrhizal Fungi (AMF; which can increase P uptake). Both N and P fertilization, as well as their interaction significantly (P <0.01) affected N2O emission. Highest N2O emissions (2.38 kg N2O-N ha(-1)) were measured at highest N application rates without P fertilization or AMF. At the highest N application rate, N2O fluxes were lowest (0.71 kg N2O-N ha(-1)) with both P fertilization and AMF. The N2O emission factors decreased with 50 % when P fertilization was applied. Our results illustrate the importance of the judicious use of all nutrients to minimize N2O emission, and thereby further underline the intimate link between sound agronomic practice and prudent soil GHG management.
Assessing vegetation change using vegetation-plot databases: a risky business
Chytry, M. ; Tichý, L. ; Hennekens, S.M. ; Schaminee, J.H.J. - \ 2014
Applied Vegetation Science 17 (2014)1. - ISSN 1402-2001 - p. 32 - 41.
long-term changes - plant-communities - phytosociological databases - species richness - grassland - forests - netherlands - drivers - decades - index
Aim Data from vegetation plots can be used for the assessment of past vegetation change in three ways: (1) comparison of old and new records from permanent plots established for vegetation monitoring; (2) revisiting historical phytosociological plots and subsequent comparison of old and new records; (3) comparison of large sets of old and new phytosociological records from the same area but different plots. Option (3) would be the cheapest in regions where large vegetation-plot databases are available, but there is a risk of incorrect results due to a spatial mismatch of old and new plots. Here we assess the accuracy of such analyses. Methods We used three data sets of permanent plots from Czech mountain bogs and Dutch oak forests and heathlands to quantify vegetation change. We selected subsets to simulate analyses based on (1) data from permanent plots or revisited phytosociological plots, i.e. containing old and new records from the same plots, (2) vegetation-plot databases with old and new records from different, randomly selected sites, and (3) vegetation-plot databases with old and new records from different but close sites. We repeated each subset selection 1000 times and analysed vegetation change in each of the three data sets and each variant of subset selection using permutational multivariate analysis of variance. Results For data sets with no actual vegetation change, analyses of some subsets simulating vegetation-plot databases incorrectly suggested significant changes. For a data set with real change, a change was detected in analyses of simulated vegetation-plot databases, but in several cases it had a different direction or magnitude to the real change. Conclusions The assessment of vegetation change using vegetation-plot databases should be either avoided or interpreted with extreme caution because of the risk of incorrect results. Analyses such as these may be used to propose hypotheses about past vegetation change, but their results should not be considered valid unless confirmed using more reliable data. In many contexts, re-visitation studies of historical phytosociological plots may be the best strategy to assess past vegetation change, while new networks of carefully stratified permanent plots are preferable for monitoring future change.
Assessing the impacts of livestock production on biodiversity in rangeland ecosystems
Alkemade, R. ; Reid, R.S. ; Berg, M. van den; Leeuw, J. de; Jeuken, M. - \ 2013
Proceedings of the National Academy of Sciences of the United States of America 110 (2013)52. - ISSN 0027-8424 - p. 20900 - 20905.
land-use changes - south-africa - diversity - conservation - assemblages - grassland - management - scenarios - responses - savanna
Biodiversity in rangelands is decreasing, due to intense utilization for livestock production and conversion of rangeland into cropland; yet the outlook of rangeland biodiversity has not been considered in view of future global demand for food. Here we assess the impact of future livestock production on the global rangelands area and their biodiversity. First we formalized existing knowledge about livestock grazing impacts on biodiversity, expressed in mean species abundance (MSA) of the original rangeland native species assemblages, through metaanalysis of peer-reviewed literature. MSA values, ranging from 1 in natural rangelands to 0.3 in man-made grasslands, were entered in the IMAGE-GLOBIO model. This model was used to assess the impact of change in food demand and livestock production on future rangeland biodiversity. The model revealed remarkable regional variation in impact on rangeland area and MSA between two agricultural production scenarios. The area of used rangelands slightly increases globally between 2000 and 2050 in the baseline scenario and reduces under a scenario of enhanced uptake of resource-efficient production technologies increasing production [high levels of agricultural knowledge, science, and technology (high-AKST)], particularly in Africa. Both scenarios suggest a global decrease in MSA for rangelands until 2050. The contribution of livestock grazing to MSA loss is, however, expected to diminish after 2030, in particular in Africa under the high-AKST scenario. Policies fostering agricultural intensification can reduce the overall pressure on rangeland biodiversity, but additional measures, addressing factors such as climate change and infrastructural development, are necessary to totally halt biodiversity loss.
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