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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Does topsoil removal in grassland restoration benefit both soil nematode and plant communities?
Resch, Monika Carol ; Schütz, Martin ; Graf, Ulrich ; Wagenaar, Roel ; Putten, Wim H. ; Risch, Anita C. - \ 2019
Journal of Applied Ecology (2019). - ISSN 0021-8901
biodiversity - biological indicators - food web structure - long-term recovery - propagule availability - restoration success - semi-natural grasslands - topsoil removal

Successful restoration of semi-natural grasslands on grasslands previously subject to intensive management needs to overcome manifold barriers. These include high soil fertility, the dominance of a few fast-growing plant species, degraded soil faunal communities and missing propagules of the targeted above- and below-ground flora and fauna. A combination of removing the topsoil and introducing propagules of target plants has become one of the major tools for nature conservation agencies and practitioners to reduce soil fertility and restore former species-rich grasslands in various European countries. Using topsoil removal as a restoration measure has provoked an ongoing debate between supporting nature conservation and rejecting soil protection agencies. Although it favours species-rich plant communities, it strongly disturbs soil communities and affects physical and chemical soil properties and processes. Currently, there is a lack of long-term data to assess how restored grassland ecosystems develop and recover after topsoil removal. Here, we used two well-established bioindicators, soil nematodes and plants, to quantify restoration success of topsoil removal in comparison with alternative restoration measures and target communities 22 years after intervention. The nematode community composition indicated reduced nutrient availability in the restored systems, as was aimed at by topsoil removal. Nevertheless, after this 22-year period following topsoil removal, nematode composition and structure revealed successful recovery. Plant communities benefitted from the reduction of soil nutrients after topsoil removal as indicated by higher numbers of plant species and higher Shannon diversity. Furthermore, topsoil removal strongly promoted the re-establishment of plant species of the target plant community. Synthesis and applications. Overall, our study demonstrates how a massive intervention by topsoil removal proved successful in converting intensively managed into species-rich grasslands. This contrasts with the mild intervention of repeated mowing and removing of the harvested plant material. We show that, in the long run, potential negative effects of topsoil removal on the soil fauna can be successfully overcome and plant communities can develop into targeted species-rich grassland.

Size-dependent loss of aboveground animals differentially affects grassland ecosystem coupling and functions
Risch, A.C. ; Ochoa-Hueso, R. ; Putten, W.H. van der; Bump, J.K. ; Busse, M.D. ; Frey, B. ; Gwiazdowicz, D.J. ; Page-Dumroese, D.S. ; Vandegehuchte, M.L. ; Zimmermann, S. ; Schütz, M. - \ 2018
Nature Communications 9 (2018)1. - ISSN 2041-1723

Increasing evidence suggests that community-level responses to human-induced biodiversity loss start with a decrease of interactions among communities and between them and their abiotic environment. The structural and functional consequences of such interaction losses are poorly understood and have rarely been tested in real-world systems. Here, we analysed how 5 years of progressive, size-selective exclusion of large, medium, and small vertebrates and invertebrates—a realistic scenario of human-induced defaunation—impacts the strength of relationships between above- and belowground communities and their abiotic environment (hereafter ecosystem coupling) and how this relates to ecosystem functionality in grasslands. Exclusion of all vertebrates results in the greatest level of ecosystem coupling, while the additional loss of invertebrates leads to poorly coupled ecosystems. Consumer-driven changes in ecosystem functionality are positively related to changes in ecosystem coupling. Our results highlight the importance of invertebrate communities for maintaining ecological coupling and functioning in an increasingly defaunated world.

Aboveground mammal and invertebrate exclusions cause consistent changes in soil food webs of two subalpine grassland types, but mechanisms are system-specific
Vandegehuchte, Martijn L. ; Putten, Wim H. Van Der; Duyts, Henk ; Schütz, Martin ; Risch, Anita C. - \ 2017
Oikos 126 (2017)2. - ISSN 0030-1299 - p. 212 - 223.
Ungulates, smaller mammals, and invertebrates can each affect soil biota through their influence on vegetation and soil characteristics. However, direct and indirect effects of the aboveground biota on soil food webs remain to be unraveled. We assessed effects of progressively excluding aboveground large-, medium- and small-sized mammals as well as invertebrates on soil nematode diversity and feeding type abundances in two subalpine grassland types: short- and tall-grass vegetation. We explored pathways that link exclusions of aboveground biota to nematode feeding type abundances via changes in plants, soil environment, soil microbial biomass, and soil nutrients.

In both vegetation types, exclusions caused a similar shift toward higher abundance of all nematode feeding types, except plant feeders, lower Shannon diversity, and lower evenness. These effects were strongest when small mammals, or both small mammals and invertebrates were excluded in addition to excluding larger mammals. Exclusions resulted in a changed abiotic soil environment that only affected nematodes in the short-grass vegetation. In each vegetation type, exclusion effects on nematode abundances were mediated by different drivers related to plant quantity and quality. In the short-grass vegetation, not all exclusion effects on omni–carnivorous nematodes were mediated by the abundance of lower trophic level nematodes, suggesting that omni–carnivores also depended on other prey than nematodes.

We conclude that small aboveground herbivores have major impacts on the soil food web of subalpine short- and tall-grass ecosystems. Excluding aboveground animals caused similar shifts in soil nematode assemblages in both subalpine vegetation types, however, mechanisms turned out to be system-specific.
Data from: Aboveground mammal and invertebrate exclusions cause consistent changes in soil food webs of two subalpine grassland types, but mechanisms are system-specific
Vandegehuchte, Martijn L. ; Putten, W.H. van der; Duyts, H. ; Schütz, Martin ; Risch, Anita C. - \ 2016
soil ecology - above-belowground interactions - herbivory
Data_OIK-03341.R2.csv contains the data on nematode feeding type abundances and community indices, as well as the data used in the Structural Equation Models of the progressive aboveground mammal and invertebrate exclusion effects on the abundance of bacterivorous, fungivorous, plant-feeding and omni-carnivorous nematode abundance via pathways of plants, soil nutrients, soil microbial biomass, and soil environment in both short- and tall-grass vegetation
Humpback and minke whale acoustic presence with reference to fish sounds and ambient noise levels at Saba Bank, Caribbean Windward Dutch Islands
Risch, D. ; Haan, D. de - \ 2016
IMARES (Report / IMARES C067/16) - 22 p.
megaptera novaeangliae - whales - acoustics - sounds - netherlands antilles - monitoring - saba - walvissen - geluidsleer - geluiden - nederlandse antillen
The Antillean Island chain is a known breeding and calving ground for North Atlantic humpback whales (Megaptera novaeangliae). However, while most research efforts for this species have focused on the largest aggregation of whales, located on Silver Bank, off the northern coast of the Dominican Republic, there are still significant knowledge gaps with respect to humpback whale movements along the Antillean Island chain. Even less is known about the spatio-temporal distribution of other marine mammal and fish species in the region. This report summarizes analysis results of acoustic data (10-8000 Hz effective analysis bandwidth recorded at a 25% duty cycle), recorded on the north east of Saba Bank from October 2011 to April 2012. The results show the consistent presence of humpback whales in the vicinity of Saba Bank during their winter breeding season, occasional presence of minke whales and the presence of sound producing fish assemblages. Humpback whale song occurred from the end of December to the end of the recording period in April. From February to April humpback whale song was recorded on more than 89 % of all recording days, though it occurred most frequently in March. All recording days in March showed song presence, with an average of 8.5 ± 2.8 (mean ± SE) hours of recorded song per day. In contrast, for minke whale (Balaenoptera acutorostrata) 48 pulse trains (n = 32) were detected less frequently between February to April 2012. A variety of unidentified fish sounds were present throughout the recordings. Although the occurrence of these sounds was not quantified, notable fish choruses (e.g. grouper spp. Epinephelinae) consisting of one to two distinct pulsed calls in the frequency range of 100 - 600 Hz were documented from October to December 2011 in particular. The results of this pilot project highlight the feasibility of using passive acoustic monitoring (PAM) to explore year-round marine mammal and fish presence and distribution in otherwise understudied and remote field sites.
Aboveground vertebrate and invertebrate herbivore impact on net N mineralization in subalpine grasslands
Risch, A.C. ; Schütz, Martin ; Vandegehuchte, Martijn L. ; Putten, W.H. Van Der; Duyts, Henk ; Raschein, Ursina ; Gwiazdowicz, D.J. ; Busse, M.D. ; Page-Dumroese, D.S. ; Zimmermann, Stephan - \ 2015
Ecology 96 (2015)12. - ISSN 0012-9658 - p. 3312 - 3322.
Above-belowground interactions - Exclosure types - Functionally different herbivores - Herbivory - Nutrient cycling - Plant biomass - Plant properties - Soil arthropods - Soil mites - Soil properties - Subalpine grasslands - Switzerland

Aboveground herbivores have strong effects on grassland nitrogen (N) cycling. They can accelerate or slow down soil net N mineralization depending on ecosystem productivity and grazing intensity. Yet, most studies only consider either ungulates or invertebrate herbivores, but not the combined effect of several functionally different vertebrate and invertebrate herbivore species or guilds. We assessed how a diverse herbivore community affects net N mineralization in subalpine grasslands. By using size-selective fences, we progressively excluded large, medium, and small mammals, as well as invertebrates from two vegetation types, and assessed how the exclosure types (ET) affected net N mineralization. The two vegetation types differed in long-term management (centuries), forage quality, and grazing history and intensity. To gain a more mechanistic understanding of how herbivores affect net N mineralization, we linked mineralization to soil abiotic (temperature; moisture; NO3 -, NH4 +, and total inorganic N concentrations/pools; C, N, P concentrations; pH; bulk density), soil biotic (microbial biomass; abundance of collembolans, mites, and nematodes) and plant (shoot and root biomass; consumption; plant C, N, and fiber content; plant N pool) properties. Net N mineralization differed between ET, but not between vegetation types. Thus, shortterm changes in herbivore community composition and, therefore, in grazing intensity had a stronger effect on net N mineralization than long-term management and grazing history. We found highest N mineralization values when only invertebrates were present, suggesting that mammals had a negative effect on net N mineralization. Of the variables included in our analyses, only mite abundance and aboveground plant biomass explained variation in net N mineralization among ET. Abundances of both mites and leaf-sucking invertebrates were positively correlated with aboveground plant biomass, and biomass increased with progressive exclusion. The negative impact of mammals on net N mineralization may be related partially to (1) differences in the amount of plant material (litter) returned to the belowground subsystem, which induced a positive bottom-up effect on mite abundance, and (2) alterations in the amount and/or distribution of dung, urine, and food waste. Thus, our results clearly show that short-term alterations of the aboveground herbivore community can strongly impact nutrient cycling within ecosystems independent of long-term management and grazing history.

Seasonal migrations of North Atlantic minke whales: novel insights from large-scale passive acoustic monitoring netsworks
Risch, D. ; Castellote, M. ; Clark, C.W. ; Lucke, K. ; Verdaat, J.P. - \ 2014
Movement Ecology 2 (2014). - ISSN 2051-3933 - 17 p.
Background - Little is known about migration patterns and seasonal distribution away from coastal summer feeding habitats of many pelagic baleen whales. Recently, large-scale passive acoustic monitoring networks have become available to explore migration patterns and identify critical habitats of these species. North Atlantic minke whales (Balaenoptera acutorostrata) perform seasonal migrations between high latitude summer feeding and low latitude winter breeding grounds. While the distribution and abundance of the species has been studied across their summer range, data on migration and winter habitat are virtually missing. Acoustic recordings, from 16 different sites from across the North Atlantic, were analyzed to examine the seasonal and geographic variation in minke whale pulse train occurrence, infer information about migration routes and timing, and to identify possible winter habitats. Results - Acoustic detections show that minke whales leave their winter grounds south of 30° N from March through early April. On their southward migration in autumn, minke whales leave waters north of 40° N from mid-October through early November. In the western North Atlantic spring migrants appear to track the warmer waters of the Gulf Stream along the continental shelf, while whales travel farther offshore in autumn. Abundant detections were found off the southeastern US and the Caribbean during winter. Minke whale pulse trains showed evidence of geographic variation, with longer pulse trains recorded south of 40° N. Very few pulse trains were recorded during summer in any of the datasets. Conclusion - This study highlights the feasibility of using acoustic monitoring networks to explore migration patterns of pelagic marine mammals. Results confirm the presence of minke whales off the southeastern US and the Caribbean during winter months. The absence of pulse train detections during summer suggests either that minke whales switch their vocal behaviour at this time of year, are absent from available recording sites or that variation in signal structure influenced automated detection. Alternatively, if pulse trains are produced in a reproductive context by males, these data may indicate their absence from the selected recording sites. Evidence of geographic variation in pulse train duration suggests different behavioural functions or use of these calls at different latitudes.
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