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.

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Native and Non-Native Plants Provide Similar Refuge to Invertebrate Prey, but Less than Artificial Plants
Grutters, B.M.C. ; Pollux, B.J.A. ; Verberk, W.C.E.P. ; Bakker, E.S. - \ 2015
PLoS One 10 (2015)4. - ISSN 1932-6203 - 11 p.
submerged aquatic vegetation - structural complexity - habitat complexity - foraging success - intraguild predation - largemouth bass - fish predation - hunting mode - body-size - food-web
Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant’s native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (Daphnia pulex, Gammarus pulex and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton perfoliatus) and non-native plants (Vallisneria spiralis, Myriophyllum heterophyllum, Cabomba caroliniana). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: Cyprinus carpio carpio and dragonfly larvae: Anax imperator) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (Ceratophyllum demersum), may interact with structural complexity to play a key role in refuge provisioning to specific prey (Gammarus pulex). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants.
Plant diversity and identity effects on predatory nematodes and their prey
Kostenko, O. ; Duyts, H. ; Grootemaat, S. ; Deyn, G.B. de; Bezemer, T.M. - \ 2015
Ecology and Evolution 5 (2015)4. - ISSN 2045-7758 - p. 836 - 847.
entomopathogenic nematodes - biological-control - biodiversity experiment - parasitic nematodes - food-web - soil - communities - grasslands - steinernema - populations
There is considerable evidence that both plant diversity and plant identity can influence the level of predation and predator abundance aboveground. However, how the level of predation in the soil and the abundance of predatory soil fauna are related to plant diversity and identity remains largely unknown. In a biodiversity field experiment, we examined the effects of plant diversity and identity on the infectivity of entomopathogenic nematodes (EPNs, Heterorhabditis and Steinernema spp.), which prey on soil arthropods, and abundance of carnivorous non-EPNs, which are predators of other nematode groups. To obtain a comprehensive view of the potential prey/food availability, we also quantified the abundance of soil insects and nonpredatory nematodes and the root biomass in the experimental plots. We used structural equation modeling (SEM) to investigate possible pathways by which plant diversity and identity may affect EPN infectivity and the abundance of carnivorous non-EPNs. Heterorhabditis spp. infectivity and the abundance of carnivorous non-EPNs were not directly related to plant diversity or the proportion of legumes, grasses and forbs in the plant community. However, Steinernema spp. infectivity was higher in monocultures of Festuca rubra and Trifolium pratense than in monocultures of the other six plant species. SEM revealed that legumes positively affected Steinernema infectivity, whereas plant diversity indirectly affected the infectivity of Heterorhabditis EPNs via effects on the abundance of soil insects. The abundance of prey (soil insects and root-feeding, bacterivorous, and fungivorous nematodes) increased with higher plant diversity. The abundance of prey nematodes was also positively affected by legumes. These plant community effects could not be explained by changes in root biomass. Our results show that plant diversity and identity effects on belowground biota (particularly soil nematode community) can differ between organisms that belong to the same feeding guild and that generalizations about plant diversity effects on soil organisms should be made with great caution.
Using additive modelling to quantify the effect of chemicals on phytoplankton diversuity and biomass
Viaene, K.P.J. ; Laender, F. de; Brink, P.J. van den; Janssen, C.R. - \ 2013
Science of the Total Environment 449 (2013). - ISSN 0048-9697 - p. 71 - 80.
ecological risk-assessment - fresh-water microcosms - herbicide linuron - primary producers - photosystem-ii - pond mesocosms - food-web - biodiversity - sensitivity - communities
Environmental authorities require the protection of biodiversity and other ecosystem properties such as biomass production. However, the endpoints listed in available ecotoxicological datasets generally do not contain these two ecosystem descriptors. Inferring the effects of chemicals on such descriptors from micro- or mesocosm experiments is often hampered by inherent differences in the initial biodiversity levels between experimental units or by delayed community responses. Here we introduce additive modelling to establish the effects of a chronic application of the herbicide linuron on 10 biodiversity indices and phytoplankton biomass in microcosms. We found that communities with a low (high) initial biodiversity subsequently became more (less) diverse, indicating an equilibrium biodiversity status in the communities considered here. Linuron adversely affected richness and evenness while dominance increased but no biodiversity indices were different from the control treatment at linuron concentrations below 2.4 µg/L. Richness-related indices changed at lower linuron concentrations (effects noticeable from 2.4 µg/L) than other biodiversity indices (effects noticeable from 14.4 µg/L) and, in contrast to the other indices, showed no signs of recovery following chronic exposure. Phytoplankton biomass was unaffected by linuron due to functional redundancy within the phytoplankton community. Comparing thresholds for biodiversity with conventional toxicity test results showed that standard ecological risk assessments also protect biodiversity in the case of linuron.
Top-down and bottom-up control of large herbivore populations: a review of natural and human-induced influences
Gandiwa, E. - \ 2013
Tropical conservation science 6 (2013)4. - ISSN 1940-0829 - p. 493 - 505.
gonarezhou national-park - community structure - african savannas - food-web - wildlife conservation - aboriginal overkill - trophic cascades - southern africa - body-size - ecosystems
The question whether animal populations are top-down and/or bottom-up controlled has motivated a thriving body of research over the past five decades. In this review I address two questions: 1) how do top-down and bottom-up controls influence large herbivore populations? 2) How do human activities and control systems influence the top-down and bottom-up processes that affect large herbivore population dynamics? Previous studies suggest that the relative influence of top-down vs. bottom-up control varies among ecosystems at the global level, with abrupt shifts in control possible in arid and semi-arid regions during years with large differences in rainfall. Humans as super-predators exert top-down control on large wild herbivore abundances through hunting. However, through fires and livestock grazing, humans also exert bottom-up controls on large wild herbivore abundances through altering resource availability, which influences secondary productivity. This review suggests a need for further research, especially on the human-induced top-down and bottom-up control of animal populations in different terrestrial ecosystems.
Harbour porpoises Phocoena phocoena in the Eastern Scheldt: A resident Stock or trapped by a storm surge barrier?
Jansen, O.E. ; Aarts, G.M. ; Reijnders, P.J.H. - \ 2013
PLoS One 8 (2013)3. - ISSN 1932-6203
sea-level rise - stable-isotope analysis - food-web - feeding ecology - carbon isotopes - marine mammals - north-sea - nitrogen - diet - delta-c-13
Coastal protection measures are planned and executed worldwide to combat the effects of global warming and climate change, in particular the acceleration of sea level rise, higher storm surge flooding and extensive coastal inundation. The extent to which these defensive measures may impact coastal and estuarine ecosystems is still poorly understood. Since the building of a storm surge barrier, movement of harbour porpoises Phocoena phocoena in and out of the Eastern Scheldt tidal bay (SW-Netherlands) may be limited. To measure residency, porpoises stranded along the Dutch North Sea coast between 2006 and 2008 were sampled for muscle (n = 102) and bone tissue (n = 118), of which 9 muscle (8.8%) and 12 bone samples (10.2%) were collected from animals stranded within the Eastern Scheldt. Stable carbon (d13C) was analysed to get insight into the habitat use and residency of porpoises in the Eastern Scheldt. Our data showed significantly higher d13C values in the muscle of porpoises stranded within the Eastern Scheldt (µ = -17.7‰, SD = 0.4‰) compared to animals stranded along the Dutch coast (µ = -18.3‰, SD = 0.5‰). This suggests that most porpoises stranded in the Eastern Scheldt foraged there for a longer period. The distinct d13C signature of animals from the Eastern Scheldt was not observed in bone tissue, suggesting a relatively recent shift in habitat use rather than life-long residency of porpoises within the Eastern Scheldt. The high number of strandings within the Eastern Scheldt suggests a higher mortality rate compared to the Dutch coastal zone. Our study indicates that along with other changes in the physical environment, the storm surge barrier may play an important role in determining the residency of porpoises in the Eastern Scheldt, and that the area might act as an ecological trap for porpoises entering it.
Matgrass sward plant species benefit from soil organisms
Brinkman, E.P. ; Raaijmakers, C.E. ; Bakx-Schotman, J.M.T. ; Hannula, S.E. ; Kemmers, R.H. ; Boer, W. de; Putten, W.H. van der - \ 2012
Applied Soil Ecology 62 (2012). - ISSN 0929-1393 - p. 61 - 70.
restoration ecology - mycorrhizal fungi - borne fungi - fatty-acids - food-web - grassland - diversity - communities - succession - nematodes
Soil organisms are important in the structuring of plant communities. However, little is known about how to apply this knowledge to vegetation management. Here, we examined if soil organisms may promote plant species of characteristic habitats, and suppress plant species of disturbed habitats. We classified nineteen fields into four types: characteristic and disturbed matgrass swards and successfully and unsuccessfully restored fields. We recorded the vegetation composition and measured biotic and abiotic soil characteristics of the sites. In a pot experiment, we mixed non-sterilized (with soil organisms) or sterilized (without soil organisms) soil inoculum from each field with a common sterilized background soil. We planted seedlings of characteristic matgrass species Antennaria dioica and Nardus stricta, of disturbance indicators Deschampsia flexuosa and Agrostis capillaris, or a combination of the four species. At harvest, we measured root and shoot dry mass of all plants. The vegetation composition of characteristic matgrass swards differed from the disturbed and unsuccessfully restored fields. The successfully restored fields were intermediate. The composition of the nematode community tended to follow the same pattern. In the pot experiment, addition of soil organisms increased the biomass of A. dioica, N. stricta and D. flexuosa, but decreased the biomass of A. capillaris. However, the effect of soil organisms on plant biomass was not related to field type. A. dioica showed a large variation in biomass in non-sterilized, but not in sterilized soil. Soil organisms from some sites increased plant biomass, whereas soil organisms from other sites did not. The biomass of characteristic matgrass plants was lower in the presence of plants from disturbed swards, irrespective of the presence of soil organisms. Probably A. capillaris was so much larger than the other species, that this overruled effects of added soil organisms. Soil organisms promoted growth of plant species characteristic of matgrass swards, whereas they reduced growth of a plant species characteristic of disturbed fields. Soil organisms did not change the outcome of plant interactions, which was won by a disturbance indicator. Nevertheless, measurement of the growth stimulating capacity of a soil may be used to assess opportunities for reintroduction of characteristic plant species.
The resilience and resistance of an ecosystem to a collapse of diversity
Downing, A.S. ; Nes, E.H. van; Mooij, W.M. ; Scheffer, M. - \ 2012
PLoS One 7 (2012)9. - ISSN 1932-6203
lake victoria - stable states - east-africa - coral-reefs - nile perch - food-web - biodiversity - productivity - communities - populations
Diversity is expected to increase the resilience of ecosystems. Nevertheless, highly diverse ecosystems have collapsed, as did Lake Victoria's ecosystem of cichlids or Caribbean coral reefs. We try to gain insight to this paradox, by analyzing a simple model of a diverse community where each competing species inflicts a small mortality pressure on an introduced predator. High diversity strengthens this feedback and prevents invasion of the introduced predator. After a gradual loss of native species, the introduced predator can escape control and the system collapses into a contrasting, invaded, low-diversity state. Importantly, we find that a diverse system that has high complementarity gains in resilience, whereas a diverse system with high functional redundancy gains in resistance. Loss of resilience can display early-warning signals of a collapse, but loss of resistance not. Our results emphasize the need for multiple approaches to studying the functioning of ecosystems, as managing an ecosystem requires understanding not only the threats it is vulnerable to but also pressures it appears resistant to
Natural born indicators: Great cormorant Phalacrocorax carbo (Aves: Phalacrocoracidae) as monitors of river discharge influence on estuarine ichthyofauna
Dias, E. ; Morais, P. ; Leopold, M.F. ; Campos, J. ; Antunes, C. - \ 2012
Journal of Sea Research 73 (2012). - ISSN 1385-1101 - p. 101 - 108.
double-crested cormorants - australian estuary - fish farm - food-web - diet - seabirds - variability - recruitment - management - abundance
The ecological traits of piscivorous marine birds have been acknowledged to reflect ecosystem changes. We used the great cormorant as our indicator species in the Minho estuary (NW-Iberian Peninsula, Europe) to assess the temporal variation of their diet and the factors that could influence that variation. Pellets were collected in a night roost, located centrally in the estuary, during two consecutive wintering periods (2005–2006 and 2006–2007). The great cormorant population showed a high degree of feeding plasticity and most of the variation in cormorants' diet was attributed to river discharge fluctuations. Overall, during periods of increased river discharge, marine and marine opportunistic species disappeared from diet, whereas freshwater species increased. The cormorants in this study were using a roost in the middle of the estuary, so they were facing a changing food base over time, in accordance to variation in river discharges. The birds did not keep their diet constant but rather took what became locally available, notwithstanding their broad foraging range. Therefore, we suggest that great cormorants may be considered good samplers of local ichthyofauna and thus, temporal variation in the local prey can be followed by analyzing cormorants' diet.
Site-specific distribution of the bivalve Scrobicularia plana along the European coast
Santos, S. ; Aarts, G.M. ; Luttikhuizen, P. ; Campos, J. ; Piersma, T. ; Veer, H.W. van der - \ 2012
Marine Ecology Progress Series 471 (2012). - ISSN 0171-8630 - p. 123 - 134.
spatial-distribution patterns - wadden sea - environmental variables - estuarine macrobenthos - population-dynamics - landscape-scale - food-web - invertebrates - community - ecology
The development and maintenance of spatial patterns and the way they affect the dynamics of populations and ecosystems is a key issue in ecology. Since each individual and each species experiences the environment on a unique range of scales, it is vital to determine the spatial scales across which organisms interact with each other and the structuring influence of their environments, which can be achieved by analyzing species’ distribution patterns. Here, the spatial variation in the distribution of Scrobicularia plana is described for 4 intertidal areas along the species’ distributional range. Spatial autocorrelation correlograms based on Moran’s coefficient reveal that while the Trondheim (Norway) population was randomly distributed, at Minho (Portugal), the Westerschelde, and the Wadden Sea (both in The Netherlands) populations were aggregated. Patch diameter varied from 150 to 1250 m, in Minho and Westerschelde, respectively; while in the Wadden Sea, patches of 4 to 10 km were detected. Comparisons of spatial patterns with those of other co-occurring bivalve species (Abra tenuis, Cerastoderma edule, and Macoma balthica) revealed that S. plana’s distribution was generally patchier. The distribution of S. plana was correlated with sediment type at Westerschelde and Trondheim, but not Minho. The observed differences in distribution patterns and their correlation with environmental factors reveal that spatial patterns of S. plana are site-specific rather than species-specific.
Crop resistance traits modify the effects of an aboveground herbivore, brown planthopper, on soil microbial biomass and nematode community via changes to plant performance.
Huang, J. ; Liu, M. ; Chen, F. ; Griffiths, B.S. ; Chen, X. ; Johnson, S.N. ; Hu, F. - \ 2012
Soil Biology and Biochemistry 49 (2012). - ISSN 0038-0717 - p. 157 - 166.
experimental grassland community - below-ground communities - animal trophic groups - nilaparvata-lugens - food-web - nutrient dynamics - carbon allocation - shoot herbivores - rice cultivars - root
Plant-mediated effects of aboveground herbivory on the belowground ecosystem are well documented, but less attention has been paid to agro-ecosystems and in particular how crop cultivars with different traits (i.e. resistance to pests) shape such interactions. A fully factorial experiment was conducted using four rice cultivars with different insect-resistance, with and without the aboveground herbivore Nilaparvata lugens (brown planthopper), and to test two hypotheses (1) aboveground herbivory affects the soil microbial biomass and nematode community by altering plant performance and soil resource availability and (2) herbivory effects will depend on cultivar resistance traits. Our results suggested that cultivar resistance mediated both herbivory intensity and herbivore effects on plant performance. N. lugens decreased the availability of soil resources (soluble sugars, amino acids, organic acids, dissolved organic carbon and nitrogen), microbial biomass and percentages of bacterivores when feeding on a susceptible cultivar but increased them in a resistant cultivar. However, total nematode abundance and the percentage of plant-parasitic nematodes responded in the opposite way, increasing under a susceptible cultivar and decreasing under a resistant cultivar. The development of plant-parasites under resistant cultivars before aboveground herbivory might contribute to their resistance traits. Our findings provide evidence that N. lugens significantly reversed the pattern of soil resource availability, microbial biomass and nematode community structure (abundance and trophic composition) across cultivars with distinct resistance. In the presence of aboveground pests, the agronomic use of resistant rice cultivars could also control populations of plant-parasites and promote soil resource availability, further extended to higher trophic level of soil food web.
Feeding ecology of harbour porpoises: stable isotope anlaysis of carbon and nitrogen in muscle and bone
Jansen, O.E. ; Aarts, G.M. ; Das, K. ; Lepoint, G. ; Michel, L. ; Reijnders, P.J.H. - \ 2012
Marine Biology Research 8 (2012)9. - ISSN 1745-1000 - p. 829 - 841.
phocoena-phocoena l - southern north-sea - marine mammals - food-web - stomach contents - adjacent waters - animal-tissues - diet - delta-c-13 - collagen
Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d13C and d15N) were analysed in muscle and bone samples collected from 157 porpoises stranded along the Dutch coast (2006–2008). In addition, samples from 30 prey species were analysed. Prey samples showed high d15N values in species of higher trophic level. In addition, geographic differences in isotopic composition were found, with higher d15N and d13C values in prey from more southern, coastal and estuarine areas. Based on muscle d15N values, we found neonatal enrichment and that larger porpoises, in particular males, seem to feed on lower trophic level species, compared to smaller individuals. Also bone d15N values show that larger animals had fed on lower trophic levels in distant times. Porpoises from the Eastern Scheldt reveal distinct d13C values in muscle, but not in bone. This shows that these animals had foraged in the Eastern Scheldt for a longer time period but were not born there. Seasonal variation in bone d15N and d13C values revealed two distinct groups of porpoises along the Dutch coast, a winter group (mainly males) that migrated from neighbouring regions and a Dutch subpopulation in summer. These results furthered our insight about shifts in trophic level and feeding location of harbour porpoises from the southern North Sea over time
Soil macroinvertebrates' abundance and diversity in home gardens in Tabasco, Mexico, vary with soil texture, organic matter and vegetation cover
Huerta, E. ; Wal, J.C. van der - \ 2012
European Journal of Soil Biology 50 (2012)May-June. - ISSN 1164-5563 - p. 68 - 75.
terrestrial ecosystems - generalist predators - food-web - biodiversity - conservation - homegardens - patterns - forest - plant - agroecosystems
We studied the composition of soil invertebrate communities and vegetation in 50 home gardens in the humid tropical lowlands of Tabasco, Mexico, located in five geomorphological regions. Five monoliths were made in each home garden and soil invertebrates were hand sorted, weighed and classified to morhospecies, functional groups and orders. We determined pH, organic matter, available phosphorus and texture in composed soil samples from each home garden. We determined the botanical name of trees, their diameter at breast height, height, and crown diameter, calculated tree density, tree cover, and biomass per hectare. We found 45 soil invertebrate morphospecies, which belonged to 12 Orders or taxonomical groups. Endogeic macroinvertebrates were significantly more abundant in the fluvial plains, hills, and mountains than in the coastal plains (F = 9.64 p <0.05). Path analysis produced a significant model, wherein soil organic matter influenced earthworm abundance (T = 3.28, p <0.05), while tree cover significantly influenced abundance of litter fragmenters (T = 3.16, p <0.05). Morphospecies richness was not related with tree species diversity. Canonical correspondence analysis with 67% of inertia on principal axes, showed how contents of soil organic matter, clay and silt were associated with earthworms abundance, while abundance of hymenoptera was associated with silt content. Interactions between plants and soil macroinvertebrates varied among regions. The coastal region showed a strong correlation between the abundance of palm trees (Coco nucifera), arachnida and isoptera morphospecies. The abundance of Gliricidia sepium in different regions showed a strong correlation with the abundance of earthworms
Resonance of plankton communities with temperature fluctuations
Beninca, E. ; Dakos, V. ; Nes, E.H. van; Huisman, J. ; Scheffer, M. - \ 2011
American Naturalist 178 (2011)4. - ISSN 0003-0147 - p. E85 - E95.
colored environmental noise - predator-prey system - food-web - population-dynamics - sustained oscillations - extinction risk - chaos - time - phytoplankton - variability
The interplay between intrinsic population dynamics and environmental variation is still poorly understood. It is known, however, that even mild environmental noise may induce large fluctuations in population abundances. This is due to a resonance effect that occurs in communities on the edge of stability. Here, we use a simple predator-prey model to explore the sensitivity of plankton communities to stochastic environmental fluctuations. Our results show that the magnitude of resonance depends on the timescale of intrinsic population dynamics relative to the characteristic timescale of the environmental fluctuations. Predator-prey communities with an intrinsic tendency to oscillate at a period T are particularly responsive to red noise characterized by a timescale of [Formula: see text]. We compare these theoretical predictions with the timescales of temperature fluctuations measured in lakes and oceans. This reveals that plankton communities will be highly sensitive to natural temperature fluctuations. More specifically, we demonstrate that the relatively fast temperature fluctuations in shallow lakes fall largely within the range to which rotifers and cladocerans are most sensitive, while marine copepods and krill will tend to resonate more strongly with the slower temperature variability of the open ocean
Cadmium Accumulation in Small Mammals: Species Traits, Soil Properties, and Spatial Habitat Use
Brink, N.W. van den; Lammertsma, D.R. ; Dimmers, W.J. ; Boerwinkel, M.C. - \ 2011
Environmental Science and Technology 45 (2011)17. - ISSN 0013-936X - p. 7497 - 7502.
mice apodemus-sylvaticus - heavy-metal concentrations - river floodplains - food-web - earthworms - lead - diet - bioaccumulation - stressors - pollution
In this study, the impact of species-specific spatial habitat use, diet preferences, and soil concentrations and properties on the accumulation of cadmium in small mammals was investigated. The results show that for the wood mouse (Apodemus sylvaticus), a mobile species with a large range in diet composition, accumulation of cadmium was not related to local soil concentrations or soil properties, but to diet preferences. For the common vole (Microtus arvalis), a nonmobile, specific feeding species, accumulation of cadmium was related to local soil concentrations or properties. For the bank vole (Myodes glareolus), a species with a smaller home range than the wood mouse but a broader diet spectrum than the common vole, both local soil properties and diet appeared to affect the cadmium accumulation in the kidneys. The results of this field study show that species-specific traits of small mammals are important determinants of accumulation of cadmium on a local scale. For site-specific assessment of risks of contaminants, such information is essential in order to understand exposure dynamics
Organic amendments and their influences on plant-parasitic and free-living nematodes: a promising method for nematode management?
Thoden, T.C. ; Korthals, G.W. ; Termorshuizen, A.J. - \ 2011
Nematology 13 (2011)2. - ISSN 1388-5545 - p. 133 - 153.
bacterial-feeding nematodes - root-knot nematode - soil microbial communities - nitrogen mineralization - pratylenchus-penetrans - cover crops - biological-control - food-web - bacterivorous nematodes - pyrrolizidine alkaloids
The use of organic soil amendments, such as green manures, animal manures, composts or slurries, certainly has many advantageous aspects for soil quality and is suggested as a promising tool for the management of plant-parasitic nematodes. However, during a recent literature survey we also found numerous studies reporting an increase of plant-parasitic nematodes after the use of organic amendments. Therefore, we critically re-evaluated the usefulness of organic amendments for nematode management and suggest possible mechanisms for a stimulation of plant-parasitic nematodes, as well as mechanisms that might be causing a reduction of plant-parasitic nematodes. In addition, we also elucidate a possible mechanism that might be responsible for the observed overall positive effects of organic amendments on crop yields. It is likely that a significant part of this is, inter alia, due to the proliferation of non-pathogenic, free-living nematodes and their overall positive effects on soil microbial populations, organic matter decomposition, nutrient availability, plant morphology and ecosystem stability.
Vertebrate herbivores influence soil nematodes by modifying plant communities
Veen, C.F. ; Olff, H. ; Duyts, H. ; Putten, W.H. van der - \ 2010
Ecology 91 (2010)3. - ISSN 0012-9658 - p. 828 - 835.
below-ground biota - microbial responses - grassland ecosystem - food-web - diversity - vegetation - nitrogen - defoliation - nutrients - patterns
Abiotic soil properties, plant community composition, and herbivory all have been reported as important factors influencing the composition of soil communities. However, most studies thus far have considered these factors in isolation, whereas they strongly interact in the field. Here, we study how grazing by vertebrate herbivores influences the soil nematode community composition of a floodplain grassland while we account for effects of grazing on plant community composition and abiotic soil properties. Nematodes are the most ubiquitous invertebrates in the soil. They include a variety of feeding types, ranging from microbial feeders to herbivores and carnivores, and they perform key functions in soil food webs. Our hypothesis was that grazing affects nematode community structure and composition through altering plant community structure and composition. Alternatively, we tested whether the effects of grazing may, directly or indirectly, run via changes in soil abiotic properties. We used a long-term field experiment containing plots with and without vertebrate grazers (cattle and rabbits). We compared plant and nematode community structure and composition, as well as a number of key soil abiotic properties, and we applied structural equation modeling to investigate four possible pathways by which grazing may change nematode community composition. Aboveground grazing increased plant species richness and reduced both plant and nematode community heterogeneity. There was a positive relationship between plant and nematode diversity indices. Grazing decreased the number of bacterial-feeding nematodes, indicating that in these grasslands, top-down control of plant production by grazing leads to bottom-up control in the basal part of the bacterial channel of the soil food web. According to the structural equation model, grazing had a strong effect on soil abiotic properties and plant community composition, whereas plant community composition was the main determinant of nematode community composition. Other pathways, which assumed that grazing influenced nematode community composition by inducing changes in soil abiotic properties, did not significantly explain variation in nematode community composition. We conclude that grazing-induced changes in nematode community composition mainly operated via changes in plant community composition. Influences of vertebrate grazers on soil nematodes through modification of abiotic soil properties were of less importance.
Nematode succession during composting and the potential of the nematode community as an indicator of compost maturity
Steel, H. ; Peña, E. de la; Fonderie, P. ; Willekens, K. ; Borgonie, G. ; Bert, W. - \ 2010
Pedobiologia 53 (2010)3. - ISSN 0031-4056 - p. 181 - 190.
plant-parasitic nematodes - municipal solid-waste - bacterivorous nematodes - bacterial community - organic amendments - biological-control - enzyme-activities - faunal analysis - soil nematodes - food-web
One of the key issues in compost research is to assess when the compost has reached a mature stage. The maturity status of the compost determines the quality of the final soil amendment product. The nematode community occurring in a Controlled Microbial Composting (CMC) process was analyzed with the objective of assessing whether the species composition could be used as a bio-indicator of the compost maturity status. The results obtained here describe the major shifts in species composition that occur during the composting process. Compared to terrestrial ecosystems, nematode succession in compost differs mainly in the absence of K-strategists and numerical importance of diplogastrids. At the beginning of the composting process (thermophilic phase), immediately after the heat peak, the nematode population is primarily built by bacterial feeding enrichment opportunists (cp-1) (Rhabditidae, Panagrolaimidae, Diplogastridae) followed by the bacterial-feeding general opportunists (cp-2) (Cephalobidae) and the fungal-feeding general opportunists (Aphelenchoididae). Thereafter, during the cooling and maturation stage, the bacterial-feeding-predator opportunistic nematodes (Mononchoides sp.) became dominant. Finally, at the most mature stage, the fungal-feeding Anguinidae (mainly Ditylenchus filimus) were most present. Both, the Maturity Index (MI) and the fungivorous/bacterivorous ratio (f/b ratio), increase as the compost becomes more mature (ranging, respectively, from 1 to 1.86 and from 0 to 11.90). Based on these results, both indices are suggested as potential suitable tools to assess compost maturity
Distribution of perfluorinated compounds in aquatic systems in The Netherlands
Kwadijk, C.J.A.F. ; Korytar, P. ; Koelmans, A.A. - \ 2010
Environmental Science and Technology 44 (2010)10. - ISSN 0013-936X - p. 3746 - 3751.
sprague-dawley rats - perfluoroalkyl contaminants - perfluorooctane sulfonate - lake-ontario - food-web - temporal trends - acid isomers - surfactants - water - sorption
The distribution of 15 perfluorinated compounds (PFCs) among eel (Anguilla anguilla), sediment, and water was investigated for 21 locations in The Netherlands. Furthermore, for perfluorooctanesulfonate (PFOS), a 30 year time series was measured for three locations using historical eel samples. These historical samples revealed concentrations increasing by a factor of 2-4 until the mid-1990s, followed by a return to the initial levels. In the samples described here, PFOS dominated aqueous concentrations, ranging from 4.7 to 32 ng/L in water, from 0.5 to 8.7 ng/g in sediment, and from 7 to 58 ng/g in eel filet. Field-based sediment water distribution coefficients (KD) were calculated and corrected for organic carbon content (KOC), which reduced variability among samples. Log KOC ranges were 2.6-3.7 for the C7-C9 carboxylic acids and 2.2-3.2 for the C4-C8 sulfonates. Bioaccumulation factors (log BAFs) for eel ranged from 1.09-3.26 for the C7-C9 carboxylic acids to 1.4-3.3 for the C4-C8 sulfonates. Perfluoroalkyl chain length correlated well with both sorption and bioaccumulation factors. Magnitudes and trends in KD or BAF appeared to agree well with previously published laboratory data. Results imply that PFCs are mainly present in water, which is important for PFC fate modeling and risk assessment.
Soil biota community structure and abundance under agricultural intensification and extensification
Postma-Blaauw, M.B. ; Goede, R.G.M. de; Bloem, J. ; Faber, J.H. ; Brussaard, L. - \ 2010
Ecology 91 (2010)2. - ISSN 0012-9658 - p. 460 - 473.
nematode communities - food-web - management-practices - microarthropod biomass - ecosystem function - farming systems - organic-matter - maturity index - trophic levels - land-use
Understanding the impacts of agricultural intensification and extensification on soil biota communities is useful in order to preserve and restore biological diversity in agricultural soils and enhance the role of soil biota in agroecosystem functioning. Over four consecutive years, we investigated the effects of agricultural intensification and extensification (including conversion of grassland to arable land and vice versa, increased and decreased levels of mineral fertilization, and monoculture compared to crop rotation) on major soil biota group abundances and functional diversity. We integrated and compared effects across taxonomic levels to identify sensitive species groups. Conversion of grassland to arable land negatively affected both abundances and functional diversity of soil biota. Further intensification of the cropping system by increased fertilization and reduced crop diversity exerted smaller and differential effects on different soil biota groups. Agricultural intensification affected abundances of taxonomic groups with larger body size (earthworms, enchytraeids, microarthropods, and nematodes) more negatively than smaller-sized taxonomic groups (protozoans, bacteria, and fungi). Also functional group diversity and composition were more negatively affected in larger-sized soil biota (earthworms, predatory mites) than in smaller-sized soil biota (nematodes). Furthermore, larger soil biota appeared to be primarily affected by short-term consequences of conversion (disturbance, loss of habitat), whereas smaller soil biota were predominantly affected by long-term consequences (probably loss of organic matter). Reestablishment of grassland resulted in increased abundances of soil biota groups, but since not all groups increased in the same measure, the community structure was not completely restored. We concluded that larger-sized soil biota are more sensitive to agricultural intensification than smaller-sized soil biota. Furthermore, since larger-sized soil biota groups had lower taxonomic richness, we suggest that agricultural intensification exerts strongest effects on species-poor soil biota groups, thus supporting the hypothesis that biodiversity has an “insurance” function. As soil biota play an important role in agroecosystem functioning, altered soil biota abundances and functional group composition under agricultural intensification are likely to affect the functioning of the agroecosystem
Plant defence against nematodes is not mediated by changes in the soil microbial community
Wurst, S. ; Beersum, S. van; Wagenaar, R. ; Bakx-Schotman, J.M.T. ; Drigo, B. ; Janzik, I. ; Lanoue, A. ; Putten, W.H. van der - \ 2009
Functional Ecology 23 (2009)3. - ISSN 0269-8463 - p. 488 - 495.
ectoparasitic nematodes - parasitic nematodes - biological-control - root herbivory - food-web - rhizosphere - diversity - microorganisms - identity - bacteria
1. Indirect plant defence, the recruitment of antagonists of herbivores, is well-known above the ground. In spite of various soil microorganisms acting as antagonists to root herbivores, it is still largely unknown whether plants can promote antagonistic microorganisms as an indirect defence mechanism. 2. In a greenhouse study we examined whether soil microorganisms could mediate plant defence against plant-feeding nematodes. Growth, nutrient contents and root exudation of three plant species (Plantago lanceolata, Holcus lanatus, Lotus corniculatus) and the performance of nematodes and fungal communities in the rhizospheres were measured. 3. The plant species differed in their effects on plant-feeding nematodes; however, the addition of soil microorganisms did not enhance nematode control. Nematode addition changed root exudation patterns and rhizosphere fungal community structure in a plant species-specific manner. Glucose levels in the root exudates of all three examined plant species were enhanced, and P. lanceolata root exudates contained higher levels of fumaric acid when nematodes had been added. 4. We conclude that nematodes have plant species-specific effects on root exudate chemistry and rhizosphere fungal community composition, but these effects do not necessarily enhance indirect control of nematodes by antagonistic microorganisms. More studies on below-ground plant defence are definitely needed
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