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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    Trophic Regulations of the Soil Microbiome
    Thakur, Madhav P. ; Geisen, Stefan - \ 2019
    Trends in Microbiology 27 (2019)9. - ISSN 0966-842X - p. 771 - 780.
    bacteria - climate change - food webs - fungi - predators - top-down control

    The soil microbiome regulates vital ecosystem functions ranging from primary production to soil carbon sequestration. Yet, we have only begun to understand the factors regulating the soil microbiome. While the importance of abiotic factors is increasingly recognized, the roles of trophic regulations in driving the structure and function of the soil microbiome remain less explored. Here, we review the current understanding of how and when microbial and top predators of the soil shape the community structure and function of the soil microbiome via both direct and indirect effects. We finally highlight that the structure and function of the soil microbiome depend on the interactive effects among predation, plant inputs, and abiotic variables present in the soil.

    Impact of trophic ecologies on the whereabouts of nematodes in soil
    Quist, Casper W. - \ 2017
    Wageningen University. Promotor(en): J. Bakker, co-promotor(en): J. Helder. - Wageningen : Wageningen University - ISBN 9789463430814 - 129
    nematoda - spatial distribution - soil fauna - biota - trophic levels - food webs - soil ecology - soil biology - farming systems - soil types (ecological) - geostatistics - nematoda - ruimtelijke verdeling - bodemfauna - biota - trofische graden - voedselwebben - bodemecologie - bodembiologie - bedrijfssystemen - bodemtypen (ecologisch) - geostatistiek

    Soil life is highly diverse, and ecologically intricate due to myriad of biotic interactions that take place. Terrestrial nematodes have a high potential to serve as an effective and policy-relevant indicator group for ecosystem functioning and soil biodiversity. The work described in this thesis contributed to the robust mapping of nematode communities at scales relevant in both agronomic and environmental contexts. The overarching aim of the work described in this thesis was to contribute to a sound exploration of the potential of nematode communities as an indicator group for the biological condition of soils. Therefore, the distributions of a wide range of nematode taxa were studied, within and between trophic groups and in soils conditioned by various plant species and/or farming systems.

    In Chapter 2 nematode taxon-specific qPCR assays were used to pinpoint responses of nematode communities to invasive plant species Solidago gigantea in two invaded ecosystems: semi-natural grasslands and riparian floodplains. Nematode communities and fungal biomass were examined in adjacent invaded and uninvaded patches. The dominant presence of the invasive plant causes a decrease of plant species-richness and diversity, and an about twofold increase of fungal biomass. Only the density of a single group of fungivorous nematodes (Aphelenchoididea) increased, whereas the densities of two other, phylogenetically distinct lineages of fungivorous nematodes, Aphelenchidae and Diphtherophoridae, were unaffected by the local increase in fungal biomass. Apparently S. gigantea induces a local asymmetric boost of the fungal community, and only Aphelenchoididae were able to benefit from this change induced by the invasive plant.

    In Chapter 3 the outcome is shown of a test whether farming system effects are mirrored in compositional changes in nematode communities. The long-term impact of three farming systems (conventional, integrated and organic) on nematode communities was investigated at the Vredepeel, an experimental farm in the southeastern part of The Netherlands. The results showed that organic farming causes specific shifts in nematode community composition, exceeding the usually large crop-related assemblage shifts. Strongest effects were observed for the (putative) bacterivore Prismatolaimus, which was relatively common in organic fields and nearly absent in conventional and integrated farming. A reverse effect was observed for Pristionchus; this necromenic bacterivore and facultative predator made up about 7 – 21% of the total nematode community in integrated and conventional farming, whereas it was nearly absent from organic fields. The observed farming system effects suggest that specific nematode taxa might be indicative for the impact of farming practices on soil biota. Knowledge of spatial distribution patterns of soil organisms with distinct trophic preferences will contribute to our understanding of factors that maintain and regulate soil biodiversity, and is essential information to design soil sampling strategies with predictable accuracies.

    Chapter 4 deals with microscale patchiness of 45 nematode taxa (at family, genus or species-level) in arable fields and semi-natural grasslands, on marine clay, river clay or sandy soils. Contrary to our expectations, an increase of the number of cores per composite sample above 3, did not result in more accurate detection for any of the taxa under investigation (range of number of cores per composite sample: 3, 6, 12 or 24). Neither system nor soil type did influence microscale distribution. The insights in the spatial distribution of nematodes at microscale presented here, sheds light on the impact of trophic preferences on the spatial distribution of individual nematode taxa, and will allow for the design of statistically sound soil sampling strategies.

    Chapter 5 shows belowground distribution patterns of 48 nematode taxa in 12 visually homogeneous fields (each 100 x 100 m) on three soil types (marine clay, river clay and sand) and two land-use types (arable and natural grasslands) across the Netherlands. Over 35,000 nematode-taxon specific qPCR assays allowed us to quantitative analyse nematode taxa at family, genus or species level in over 1,200 soil samples. A sampling scheme was optimized for Bayesian geostatistical analysis (Integrated nested Laplace approximations; INLA). Multivariate analysis show soil type and land-use related differences in the nematode community composition, which underline the effects of environmental filtering and niche partitioning of nematodes. All individual nematode taxa together show a wide range of degrees of spatial variabilities were found (expressed by the range-parameter and the spatial variance parameter (s2spatial). No general effects were detected of soil characteristics or nematode traits (cp-value, trophic group, weight) on the spatial distribution parameters. The relatively high percentages of unexplained spatial variability – 92.5% of the variation for the range-parameter and 74% for spatial variance (s2spatial) – point at a major role of stochasticity for variability of nematode densities within fields. This study adds empirical evidence that distribution patterns of terrestrial nematodes, in areas without noticeable gradients, are driven by neutral / stochastic processes, within the boundaries set by the environment.

    In the final Chapter 6, I discuss the opportunities and challenges of the use of molecular tools in soil ecological research, the impact of trophic preferences on the whereabouts of nematodes, the use of nematode communities as indicator for soil condition and how this might be developed and applied to facilitate more sustainable ecosystem management.

    Searching for balance : stability and equilibria of food webs
    Altena, C. van - \ 2016
    Wageningen University. Promotor(en): Peter de Ruiter; J.A.P. Heesterbeek; Wolf Mooij, co-promotor(en): Lia Hemerik. - Wageningen : Wageningen University - ISBN 9789462576827 - 130
    food webs - models - interactions - ecology - biocoenosis - ecological balance - voedselwebben - modellen - interacties - ecologie - biocenose - ecologisch evenwicht

    Abstract

    How complexity of food webs relates to stability has been a subject of many studies. Often,

    unweighted connectance is used to express complexity. Unweighted connectance is

    measured as the proportion of realized links in the network. Weighted connectance, on the

    other hand, takes link weights (fluxes or feeding rates) into account and captures the shape

    of the flux distribution. Here, we used weighted connectance to revisit the relation between

    complexity and stability. We used 15 real soil food webs and determined the feeding rates

    and the interaction strength matrices. We calculated both versions of connectance, and

    related these structural properties to food web stability. We also determined the skewness

    of both flux and interaction strength distributions with the Gini coefficient. We found no

    relation between unweighted connectance and food web stability, but weighted connectance

    was positively correlated with stability. This finding challenges the notion that complexity

    may constrain stability, and supports the ‘complexity begets stability’ notion. The positive

    correlation between weighted connectance and stability implies that the more evenly flux

    rates were distributed over links, the more stable the webs were. This was confirmed by the

    Gini coefficients of both fluxes and interaction strengths. However, the most even

    distributions of this dataset still were strongly skewed towards small fluxes or weak

    interaction strengths. Thus, incorporating these distribution with many weak links via

    weighted instead of unweighted food web measures can shed new light on classical

    theories

    The soil life cycle : food webs and ecosystem services during soil transformations
    Leeuwen, J.P. van - \ 2016
    Wageningen University. Promotor(en): Peter de Ruiter; Jaap Bloem; Lia Hemerik. - Wageningen : Wageningen University - ISBN 9789462576261 - 166
    soil - food webs - ecosystem services - life cycle - soil biology - soil flora - soil fauna - bodem - voedselwebben - ecosysteemdiensten - levenscyclus - bodembiologie - bodemflora - bodemfauna

    Soil is one of the most important natural resource for life on Earth and provides important ecosystem services, such as food production, carbon sequestration, water regulation and contaminant attenuation. Soil quality, defined as the soil’s ability to provide these services, is drastically reduced in many locations and regions worldwide due to human activities. This loss in soil quality ultimately leads to soil degradation, erosion and desertification, imposing a severe and increasing risk for the growing human population. It is therefore essential that we are aware of the importance of protecting soil, and at the same time understand processes that build up and regenerate soil. The key objective of the present study was to obtain a better understanding of soil food web structure and functioning, and how these develop in stages along the soil life cycle. Using field surveys, I investigated the soil food web structure and functioning in different sites along the soil life cycle, including soils developing in glacial chronosequences, productive soils under different land use and management, and soils under risk of degradation.

    The soil food web was expected to build up in biomass and structure, be highest in the intermediate soils, and decrease in soils at or nearby degradation. This was indeed the case when comparing developing soils in the chronosequences, and comparing productive soils with degrading soils. But also land use type turned out to be very important for the structure of the soil food web. Biological measures such as biomass, activity and diversity of soil organisms, especially that of soil microarthropods, were found to be indicative for soil quality in all sites.

    I also investigated the possible role of soil organisms in the soil ecosystem functioning, in terms of soil structure formation and C and N mineralisation. Although soil organisms are known to have an important role on soil structure formation, no clear indications of such a role were found for that function in the studied sites. However, soil microbial biomass and activity, and the biomass of other trophic groups, did play a crucial role in soil ecosystem process rates, especially the C and N mineralisation rates.

    In conclusion, I have found that soil food webs assemble in a directive manner: organism biomass and activity increase with soil productivity. In productive soils, land use type and land management are the main drivers affecting soil food web structure and functioning, although this effect is limited to the topsoil. Under harsh conditions, soil organisms reach a relatively low biomass and are sensitive to aspects of intensive agricultural land use.

    Eutrophication, Nile perch and food-web interactions in south-east Lake Victoria
    Cornelissen, I.J.M. - \ 2015
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Leo Nagelkerke; R. Vijverberg. - Wageningen : Wageningen University - ISBN 9789462575660 - 163
    lates niloticus - eutrofiëring - voedselwebben - interacties - visserijbiologie - visstand - dynamica - fytoplankton - distributie - voedingsgedrag - victoriameer - tanzania - lates niloticus - eutrophication - food webs - interactions - fishery biology - fish stocks - dynamics - phytoplankton - distribution - feeding behaviour - lake victoria - tanzania

    The increasing eutrophication, the introduction of Nile perch (Lates niloticus) and the increasing fishing pressure has changed Lake Victoria tremendously the last century. Since the 1960s, eutrophication increased primary production, enabling an increase in fish production. However, eutrophication also created hypoxia pockets, which reduced the available habitats for fish. In addition, the endemic haplochromines declined, whereas the introduced Nile perch boomed in the 1980s. The Nile perch boom and increased fish production resulted in the largest freshwater fisheries of the world. However, it is unclear whether fish production can still increase with further eutrophication as maximum primary production rates may have been reached. Fish stocks fluctuate since the 1980s and in order to manage these, it is important to understand how eutrophication and fisheries affect the Nile perch population. The present study investigates the bottom-up effects of eutrophication on the Nile perch and food-web dynamics in south-east Lake Victoria. We analysed the level of eutrophication along an eutrophication gradient in the Mwanza Gulf. Phytoplankton biomass varied spatially and seasonally and was limited by nutrients in deep water and by light in shallow water. Fish distributions were dynamic, with environmental factors depth and temperature influencing Nile perch size structure and distribution patterns similarly on small and large spatial scales. Although prey densities of haplochromines and Caridina nilotica shrimp did not explain Nile perch distributions, ontogenetic diet shifts and composition were related to prey densities, suggesting an opportunistic feeding behaviour of Nile perch. Small Nile perch however, showed some preference to shrimp and Nile perch preferred haplochromines above Dagaa (Rastrineobola argentea) and juvenile Nile perch as fish prey. On a food-web level, the base of the food web was spatially and seasonally highly dynamic. The onset of rains caused a spatial differentiation in littoral/benthic and pelagic carbon sources, affecting the whole food web. Trophic levels of fish were related to the spatial variation in diet compositions. Although a large heterogeneity was found in water quality, fish distributions and food-web structure, bottom-up processes affected the food web similarly. Despite the ongoing nutrient load in Lake Victoria, water quality has improved since the 1990s. Climate forcing through increasing wind speeds increased visibility and oxygen levels. Global climate change will therefore be an important driver of the water quality and fish distributions of Lake Victoria.

    A food web model of invertebrate subtidal soft-bottom communities Part B: effects of fishery
    Schellekens, T. ; Kooten, T. van - \ 2015
    Yerseke : IMARES (Report / IMARES Wageningen UR C131/15) - 21
    zee-invertebraten - voedselwebben - modellen - aquatische gemeenschappen - zeevisserij - visserijbiologie - visserijbeheer - vistuig - natura 2000 - noordzee - marine invertebrates - food webs - models - aquatic communities - marine fisheries - fishery biology - fishery management - fishing gear - natura 2000 - north sea
    Om visserij in de Natura-2000 gebieden Noordzeekustzone en Vlakte van de Raan zodanig te reguleren, dat zij het behalen van de geformuleerde beleidsdoelen niet in de weg staat, is het VIBEG-akkoord gesloten. Kern van de afspraken vormt een ruimtelijke zonering waarmee wordt bepaald welke visserijtechnieken in welke gebieden wel of niet zijn toegestaan.
    A food web model of invertebrate subtidal soft-bottom communities Part A: model derivation and effects of productivity
    Kooten, T. van; Schellekens, T. - \ 2015
    IJmuiden : IMARES (Report / IMARES Wageningen UR C130/15) - 18
    zee-invertebraten - voedselwebben - modellen - aquatische gemeenschappen - zeevisserij - productiviteit - visserijbiologie - vistuig - natura 2000 - noordzee - marine invertebrates - food webs - models - aquatic communities - marine fisheries - productivity - fishery biology - fishing gear - natura 2000 - north sea
    Om visserij in de Natura-2000 gebieden Noordzeekustzone en Vlakte van de Raan zodanig te reguleren, dat zij het behalen van de geformuleerde beleidsdoelen niet in de weg staat, is het VIBEG-akkoord gesloten. Kern van de afspraken vormt een ruimtelijke zonering waarmee wordt bepaald welke visserijtechnieken in welke gebieden wel of niet zijn toegestaan.
    An exposure-effect approach for evaluating ecosystem-wide risks from human activities
    Knights, A.M. ; Piet, G.J. ; Jongbloed, R.H. ; Tamis, J.E. ; Robinson, L.A. - \ 2015
    ICES Journal of Marine Science 72 (2015)3. - ISSN 1054-3139 - p. 1105 - 1115.
    baltic sea - fisheries management - environmental-change - coastal ecosystems - marine ecosystems - human impact - new-zealand - food webs - support - climate
    Ecosystem-based management (EBM) is promoted as the solution for sustainable use. An ecosystem-wide assessment methodology is therefore required. In this paper, we present an approach to assess the risk to ecosystem components from human activities common to marine and coastal ecosystems. We build on: (i) a linkage framework that describes how human activities can impact the ecosystem through pressures, and (ii) a qualitative expert judgement assessment of impact chains describing the exposure and sensitivity of ecological components to those activities. Using case study examples applied at European regional sea scale, we evaluate the risk of an adverse ecological impact from current human activities to a suite of ecological components and, once impacted, the time required for recovery to pre-impact conditions should those activities subside. Grouping impact chains by sectors, pressure type, or ecological components enabled impact risks and recovery times to be identified, supporting resource managers in their efforts to prioritize threats for management, identify most at-risk components, and generate time frames for ecosystem recovery.
    Choice of resolution by functional trait or taxonomy affects allometric scaling in soil webs
    Sechi, V. ; Brussaard, L. ; Goede, R.G.M. de; Rutgers, M. ; Mulder, C. - \ 2014
    Wageningen UR
    mass-abundance scaling - food webs - functional assemblages - soil biota - unmanaged grasslands - traits - functional diversity - allometry - trophic position - body size - isometry
    Belowground organisms often display a shift in their mass-abundance scaling relationships due to environmental factors such as soil chemistry and atmospheric deposition. Here we present new empirical data that show strong differences in allometric scaling according to whether the resolution at the local scale is based on a taxonomic or a functional classification, while only slight differences arise according to soil environmental conditions. For the first time, isometry (an inverse 1∶1 proportion) is recognized in mass-abundance relationships, providing a functional signal for constant biomass distribution in soil biota regardless of discrete trophic levels. Our findings are in contrast to those from aquatic ecosystems, in that higher trophic levels in soil biota are not a direct function of increasing body mass.
    Enhanced Input of Terrestrial Particulate Organic Matter Reduces the Resilience of the Clear-Water State of Shallow Lakes: A Model Study
    Lischke, B. ; Hilt, S. ; Janse, J.H. ; Kuiper, J.J. ; Mehner, T. ; Mooij, W.M. ; Gaedke, U. - \ 2014
    Ecosystems 17 (2014)4. - ISSN 1432-9840 - p. 616 - 626.
    climate-change - food webs - humic substances - resource use - fresh-water - loch ness - land-use - carbon - ecosystem - phosphorus
    The amount of terrestrial particulate organic matter (t-POM) entering lakes is predicted to increase as a result of climate change. This may especially alter the structure and functioning of ecosystems in small, shallow lakes which can rapidly shift from a clear-water, macrophyte-dominated into a turbid, phytoplankton-dominated state. We used the integrative ecosystem model PCLake to predict how rising t-POM inputs affect the resilience of the clear-water state. PCLake links a pelagic and benthic food chain with abiotic components by a number of direct and indirect effects. We focused on three pathways (zoobenthos, zooplankton, light availability) by which elevated t-POM inputs (with and without additional nutrients) may modify the critical nutrient loading thresholds at which a clear-water lake becomes turbid and vice versa. Our model results show that (1) increased zoobenthos biomass due to the enhanced food availability results in more benthivorous fish which reduce light availability due to bioturbation, (2) zooplankton biomass does not change, but suspended t-POM reduces the consumption of autochthonous particulate organic matter which increases the turbidity, and (3) the suspended t-POM reduces the light availability for submerged macrophytes. Therefore, light availability is the key process that is indirectly or directly changed by t-POM input. This strikingly resembles the deteriorating effect of terrestrial dissolved organic matter on the light climate of lakes. In all scenarios, the resilience of the clear-water state is reduced thus making the turbid state more likely at a given nutrient loading. Therefore, our study suggests that rising t-POM input can add to the effects of climate warming making reductions in nutrient loadings even more urgent.
    Risico's van anticoagulantia rodenticides voor niet-doelsoorten en predatoren : een scan van beschikbare kennis in Europa en analyses in roofvogels uit Nederland
    Brink, N.W. van den - \ 2014
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2589) - 25
    knaagdieren - roofvogels - ecotoxicologie - predatie - voedselwebben - rodents - predatory birds - ecotoxicology - predation - food webs
    Knaagdierpopulaties kunnen zich lokaal ontwikkelen tot zeer hoge dichtheden en kunnen op deze manier een groot maatschappelijk probleem veroorzaken. Al eeuwen lang worden knaagdierplagen geassocieerd met de uitbraak van ziektes (waaronder de zwarte pest), maar ze kunnen ook economische schade toebrengen. Hierbij valt te denken aan het opeten en bederven van voedselvoorraden, transmissie van ziekteverwekkers tussen bijvoorbeeld boerderijen, terwijl tegenwoordig het knagen aan bedradingen e.d. ook een relevant probleem is. Het gedrag van deze dieren en het feit dat ze zeer snel in populatieomvang kunnen toenemen, maakt dat de bestrijding van knaagdieren continu aandacht behoeft. Er zijn verschillende methodes om knaagdieren te bestrijden.
    Belowground biodiversity and ecosystem functioning
    Bardgett, R.D. ; Putten, W.H. van der - \ 2014
    Nature 515 (2014). - ISSN 0028-0836 - p. 505 - 511.
    arbuscular mycorrhizal fungi - soil microbial communities - food webs - global patterns - ectomycorrhizal fungi - litter decomposition - neighboring plants - spatial-patterns - invasive plant - climate-change
    Evidence is mounting that the immense diversity of microorganisms and animals that live belowground contributes significantly to shaping aboveground biodiversity and the functioning of terrestrial ecosystems. Our understanding of how this belowground biodiversity is distributed, and how it regulates the structure and functioning of terrestrial ecosystems, is rapidly growing. Evidence also points to soil biodiversity as having a key role in determining the ecological and evolutionary responses of terrestrial ecosystems to current and future environmental change. Here we review recent progress and propose avenues for further research in this field.
    Boomkorvisserij: hoe voedselweb-interacties op de zeebodem het succes van visserijmaatregelen kunnen bepalen
    Kooten, T. van - \ 2014
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C127/14) - 12
    visserij - visserij-ecologie - boomkorvisserij - onderwatergronden - bodemecologie - benthos - mariene gebieden - visserijbeheer - noordzee - voedselwebben - visbestand - visstand - aquatische ecosystemen - natuurbeheer - fisheries - fisheries ecology - beam trawling - subaqueous soils - soil ecology - benthos - marine areas - fishery management - north sea - food webs - fishery resources - fish stocks - aquatic ecosystems - nature management
    Dit document is een samenvatting, met daarbij de beleidsrelevantie, van de wetenschappelijke publicatie ‘When does fishing lead to more fish? Community consequences of bottom trawl fisheries in demersal food webs ’ geschreven door Daniel van Denderen, Tobias van Kooten en Adriaan Rijnsdorp, gepubliceerd in Proceedings of the Royal Society B, vol. 280, no. 20131883 op 4 september 2013. Het doel van deze Nederlandstalige samenvatting is het ontsluiten van de conclusies uit deze publicatie voor een breder publiek, en het schetsen van de consequenties daarvan voor het Nederlandse visserij- en natuurbeheer.
    Production-ecological modelling explains the difference between potential soil N mineralisation and actual herbage N uptake
    Rashid, M.I. ; Goede, R.G.M. de; Brussaard, L. ; Bloem, J. ; Lantinga, E.A. - \ 2014
    Applied Soil Ecology 84 (2014). - ISSN 0929-1393 - p. 83 - 92.
    winter-wheat fields - nitrogen mineralization - organic-matter - food webs - grassland soils - forest soils - community - manure - earthworms - management
    We studied two different grassland fertiliser management regimes on sand and peat soils: above-ground application of a combination of organic N-rich slurry manure and solid cattle manure (SCM) vs. slit-injected, mineral N-rich slurry manure, whether or not supplemented with chemical fertiliser (non-SCM). Measurements of field N mineralisation as estimated from herbage N uptake in unfertilised plots were compared with (i) potential N mineralisation as determined from a standard laboratory soil incubation, (ii) the contribution of groups of soil organisms to N mineralisation based on production-ecological model calculations, and (iii) N mineralisation calculated according to the Dutch fertilisation recommendation for grasslands. Density and biomass of soil biota (bacteria, fungi, enchytraeids, microarthropods and earthworms) as well as net plant N-uptake were higher in the SCM input grasslands compared to the non-SCM input grasslands. The currently used method in Dutch fertilisation recommendations underestimated actual soil N supply capacity by, on average, 102 kg N ha-1 (202 vs. 304 kg ha-1 = 34%). The summed production-ecological model estimate for N mineralisation by bacteria, fungi, protozoa, and enchytraeids was 87–120% of the measured potential soil N mineralisation. Adding the modelled N mineralisation by earthworms to potential soil N mineralisation explained 98–107% of the measured herbage N uptake from soil. For all grasslands and soil biota groups together, the model estimated 105% of the measured net herbage N uptake from soil. Soil biota production-ecological modelling is a powerful tool to understand and predict N uptake in grassland, reflecting the effects of previous manure management and soil type. The results show that combining production ecological modelling to predict N supply with existing soil N tests using aerobic incubation methods, can add to a scientifically based improvement of the N fertilisation recommendations for production grasslands.
    Groei en begrazing van mosselzaad, primaire productie en picoplankton in de Waddenzee: Technisch Rapport project Meerjarig effect- en productiemetingen aan MZI's in de Westerlijke Waddenzee, Oosterschelde en Voordelta
    Kamermans, P. ; Jak, R.G. ; Jacobs, P. ; Riegman, R. - \ 2014
    Yerseke : IMARES (Rapport / IMARES Wageningen UR C187/13) - 46
    zaden - zaad verzamelen - mossels - mytilidae - schaal- en schelpdierenvisserij - waddenzee - mosselteelt - plankton - fytoplankton - zoöplankton - voedselwebben - effecten - mytilus edulis - seeds - seed collection - mussels - mytilidae - shellfish fisheries - wadden sea - mussel culture - plankton - phytoplankton - zooplankton - food webs - effects - mytilus edulis
    In het kader van het project: “Meerjarige effectmetingen aan MZI’s in de Westelijke Waddenzee en de Oosterschelde”, uitgevoerd door IMARES in opdracht van het Ministerie van LNV (thans EZ), zijn er in 2010 tot en met 2013 veldmetingen verricht bij een MZI. Centrale vraag binnen deelproject 1 betreft de mogelijke invloed van MZI’s op de draagkracht van de Waddenzee en de Oosterschelde. In dit rapport worden de resultaten gepresenteerd van het onderzoek aan de MZI’s in de Waddenzee.
    Productivity affects the density-body mass relationship of soil fauna communities
    Comor, V.N.R. ; Thakur, M.P. ; Berg, M.P. ; Bie, S. de; Prins, H.H.T. ; Langevelde, F. van - \ 2014
    Soil Biology and Biochemistry 72 (2014). - ISSN 0038-0717 - p. 203 - 211.
    intermediate disturbance hypothesis - energetic equivalence rule - plant-species richness - population-density - size relationships - food webs - salt-marsh - forest mull - rain-forest - abundance
    The productivity of ecosystems and their disturbance regime affect the structure of animal communities. However, it is not clear which trophic levels benefit the most from higher productivity or are the most impacted by disturbance. The density-body mass (DBM) relationship has been shown to reflect changes in the structure of communities subjected to environmental modifications, so far, mainly in aquatic systems. We tested how different seawater inundation frequencies and cattle grazing, which both disturbed and impacted the productivity of a terrestrial system, a salt marsh, affected the size structure of soil fauna communities, expressed by their DBM relationship. We hypothesized that either: (1) all the trophic levels of soil fauna would benefit from higher productivity (i.e., amount of litter mass), reflected by a higher Y-intercept of the DBM relationship; (2) only smaller animals would benefit, reflected by a lower slope of the relationship; (3) or only larger animals would benefit, reflected by a higher slope of the relationship. We collected a large range of soil fauna from different elevation levels in grazed and ungrazed areas, thence subjected to different levels of productivity, represented by litter mass, with the most inundated and grazed area as the least productive one. Considering that pore size must be smaller in inundated and grazed areas, productivity seemed to be a greater factor influencing species distribution than soil structure. We found slopes lower than 0.75, showing that large animals dominated the community. However, a difference between the DBM relationships of the most and least frequently inundated ungrazed sites indicated that higher productivity benefited the smaller animals. Our findings show that high productivity does not equally affect the different trophic levels of this soil fauna community, suggesting inefficient transfers of energy from one trophic level to another, as smaller species benefitted more from higher productivity.
    Interactions between microbial-feeding and predatory soil fauna trigger N2O emissions
    Thakur, M.P. ; Groenigen, J.W. van; Kuiper, I. ; Deyn, G.B. de - \ 2014
    Soil Biology and Biochemistry 70 (2014). - ISSN 0038-0717 - p. 256 - 262.
    nitrogen mineralization - enchytraeid worms - trophic cascades - food webs - raw humus - decomposition - biodiversity - nitrification - oligochaeta - microarthropods
    Recent research has shown that microbial-feeding invertebrate soil fauna species can significantly contribute to N2O emissions. However, in soil food webs microbial-feeding soil fauna interact with each other and with their predators, which affects microbial activity. To date we lack empirical tests of whether or not these interactions play a significant role in N2O emissions from soil. Therefore we studied how interactions between soil microbes, two groups of microbial-feeding soil fauna (enchytraeids and fungivorous mites) and their predators (predatory mites) affect soil N2O emissions. We hypothesized that: 1) the presence of two microbial-feeding fauna groups (enchytraeids and fungivorous mites) together increase N2O emissions more than when only a single group is present; and 2) the addition of predatory mites further enhances N2O emissions. We assembled soil food webs consisting of soil microbes, enchytraeids, fungivorous and predatory mites in microcosms with sandy loamy soil and sterilised hay as a substrate for the soil microbes. N2O emissions were measured during 56 days. We found no support for our first yet support for our second hypothesis. Addition of predatory mites to microcosms with enchytraeids and fungivorous mites increased N2O emissions significantly from 135.3 to 482.1 mg N m-2, which was also significantly higher than the control without fauna (83 mg N m-2) (P <0.001). In presence of enchytraeids, fungivorous and predatory mites, we found much higher nitrate availability at the time of the N2O peak on Day 35 (10.9 versus 5.5 mg N per kg soil without soil fauna), indicating that the major increase in N2O emissions in this treatment may be due to increased nitrification. Increased nitrification may be attributed to higher availability of N from the dead tissues of fungivorous mites and increased activity of the enchytraeids that might also have affected soil structure and contributed to increased N2O emissions. This study demonstrates the importance of interactions between microbial-feeding invertebrate soil fauna and their predators in understanding N2O emissions.
    Seabird nutrient subsidies benefit non-nitrogen fixing trees and alter species composition in South American coastal dry forests
    Havik, G. ; Catenazzi, A. ; Holmgren, M. - \ 2014
    PLoS ONE 9 (2014)1. - ISSN 1932-6203
    gulf-of-california - food webs - allochthonous input - marine subsidies - atacama desert - islands - productivity - dynamics - lizard - land
    Marine-derived nutrients can increase primary productivity and change species composition of terrestrial plant communities in coastal and riverine ecosystems. We hypothesized that sea nutrient subsidies have a positive effect on nitrogen assimilation and seedling survival of non-nitrogen fixing species, increasing the relative abundance of non-nitrogen fixing species close to seashore. Moreover, we proposed that herbivores can alter the effects of nutrient supplementation by preferentially feeding on high nutrient plants. We studied the effects of nutrient fertilization by seabird guano on tree recruitment and how these effects can be modulated by herbivorous lizards in the coastal dry forests of northwestern Peru. We combined field studies, experiments and stable isotope analysis to study the response of the two most common tree species in these forests, the nitrogen-fixing Prosopis pallida and the non-nitrogen-fixing Capparis scabrida. We did not find differences in herbivore pressure along the sea-inland gradient. We found that the non-nitrogen fixing C. scabrida assimilates marine-derived nitrogen and is more abundant than P. pallida closer to guano-rich soil. We conclude that the input of marine-derived nitrogen through guano deposited by seabirds feeding in the Pacific Ocean affects the two dominant tree species of the coastal dry forests of northern Peru in contrasting ways. The non-nitrogen fixing species, C. scabrida may benefit from sea nutrient subsidies by incorporating guano-derived nitrogen into its foliar tissues, whereas P. pallida, capable of atmospheric fixation, does not.
    Plankton dynamics under different climatic conditions in space and time
    Senerpont Domis, L.N. de; Elser, J.J. ; Huszar, V.L.M. ; Ibelings, B.W. ; Jeppesen, E. ; Kosten, S. ; Mooij, W.M. ; Roland, F. ; Sommer, U. ; Donk, E. van; Winder, M. ; Lurling, M. - \ 2013
    Freshwater Biology 58 (2013)3. - ISSN 0046-5070 - p. 463 - 482.
    north-atlantic oscillation - top-down control - amazonian floodplain lake - fresh-water cladocerans - central-european lake - driven regime shifts - high arctic lakes - shallow lakes - food webs - seasonal succession
    1.Different components of the climate system have been shown to affect temporal dynamics in natural plankton communities on scales varying from days to years. The seasonal dynamics in temperate lake plankton communities, with emphasis on both physical and biological forcing factors, were captured in the 1980s in a conceptual framework, the Plankton Ecology Group (PEG) model. 2.Taking the PEG model as our starting point, we discuss anticipated changes in seasonal and long-term plankton dynamics and extend this model to other climate regions, particularly polar and tropical latitudes. Based on our improved post-PEG understanding of plankton dynamics, we also evaluate the role of microbial plankton, parasites and fish in governing plankton dynamics and distribution. 3.In polar lakes, there is usually just a single peak in plankton biomass in summer. Lengthening of the growing season under warmer conditions may lead to higher and more prolonged phytoplankton productivity. Climate-induced increases in nutrient loading in these oligotrophic waters may contribute to higher phytoplankton biomass and subsequent higher zooplankton and fish productivity. 4.In temperate lakes, a seasonal pattern with two plankton biomass peaks - in spring and summer - can shift to one with a single but longer and larger biomass peak as nutrient loading increases, with associated higher populations of zooplanktivorous fish. Climate change will exacerbate these trends by increasing nutrient loading through increased internal nutrient inputs (due to warming) and increased catchment inputs (in the case of more precipitation). 5.In tropical systems, temporal variability in precipitation can be an important driver of the seasonal development of plankton. Increases in precipitation intensity may reset the seasonal dynamics of plankton communities and favour species adapted to highly variable environments. The existing intense predation by fish on larger zooplankters may increase further, resulting in a perennially low zooplankton biomass. 6.Bacteria were not included in the original PEG model. Seasonally, bacteria vary less than the phytoplankton but often follow its patterns, particularly in colder lakes. In warmer lakes, and with future warming, a greater influx of allochthonous carbon may obscure this pattern. 7.Our analyses indicate that the consequences of climate change for plankton dynamics are, to a large extent, system specific, depending on characteristics such as food-web structure and nutrient loading. Indirect effects through nutrient loading may be more important than direct effects of temperature increase, especially for phytoplankton. However, with warming a general picture emerges of increases in bacterivory, greater cyanobacterial dominance and smaller-bodied zooplankton that are more heavily impacted by fish predation. © 2012 Blackwell Publishing Ltd.
    Bimodality in stable isotope composition facilitates the tracing of carbon transfer from macrophytes to higher trophic levels
    Mendonca, R. ; Kosten, S. ; Lacerot, G. ; Mazzeo, N. ; Roland, F. ; Ometto, J.P. ; Paz, A. ; Bueno, O.C. ; Gomes, A.C.M.M. ; Scheffer, M. - \ 2013
    Hydrobiologia 710 (2013)1. - ISSN 0018-8158 - p. 205 - 218.
    fresh-water macrophytes - aquatic cam plant - inorganic carbon - eutrophic lake - shallow lakes - photosynthetic characteristics - concentrating mechanisms - submerged macrophytes - microbial loop - food webs
    Even though the suitability of macrophytes to act as a carbon source to food webs has been questioned by some studies, some others indicate that macrophyte-derived carbon may play an important role in the trophic transfer of organic matter in the food web of shallow lakes. To evaluate the importance of macrophytes to food webs, we collected primary producers-macrophytes and periphyton-and consumers from 19 South American shallow lakes and analyzed their carbon stable isotopes composition (d13C). Despite the diversity of inorganic carbon sources available in our study lakes, the macrophytes' d13C signatures showed a clear bimodal distribution: 13C-depleted and 13C-enriched, averaging at -27. 2 and -13. 5‰, respectively. We argue that the use of either CO2 or HCO3 - by the macrophytes largely caused the bimodal pattern in d13C signals. The contribution of carbon from macrophytes to the lake's food webs was not straightforward in most of the lakes because the macrophytes' isotopic composition was quite similar to the isotopic composition of periphyton, phytoplankton, and terrestrial carbon. However, in some lakes where the macrophytes had a distinct isotopic signature, our data suggest that macrophytes can represent an important carbon source to shallow lake food webs. © 2012 Springer Science+Business Media Dordrecht
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