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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    Facilitating foundation species : The potential for plant–bivalve interactions to improve habitat restoration success
    Gagnon, Karine ; Rinde, Eli ; Bengil, Elizabeth G.T. ; Carugati, Laura ; Christianen, Marjolijn J.A. ; Danovaro, Roberto ; Gambi, Cristina ; Govers, Laura L. ; Kipson, Silvija ; Meysick, Lukas ; Pajusalu, Liina ; Tüney Kızılkaya, İnci ; Koppel, Johan van de; Heide, Tjisse van der; Katwijk, Marieke M. van; Boström, Christoffer - \ 2020
    Journal of Applied Ecology 57 (2020)6. - ISSN 0021-8901
    bivalves - co-restoration - ecosystem engineers - facilitation - habitat restoration - plant–bivalve interactions - salt marsh - seagrass

    Vegetated marine and freshwater habitats are being increasingly lost around the world. Habitat restoration is a critical step for conserving these valuable habitats, but new approaches are needed to increase restoration success and ensure their survival. We investigated interactions between plants and bivalves through a review and analysis of 491 studies, determined the effects, mechanisms and key environmental variables involved in and driving positive and negative interactions, and produced guidelines for integrating positive interactions into restoration efforts in different habitats. Fifty per cent of all interactions (both correlative and experimental studies) were positive. These were predominant between epifaunal bivalves and plants in all habitats, and between infaunal bivalves and plants in subtidal habitats. Plants primarily promoted bivalve survival and abundance by providing substrate and shelter, while bivalves promoted plant growth and survival by stabilizing and fertilizing the sediment, and reducing water turbidity. The prevalence of positive interactions increased with water temperature in subtidal habitats, but decreased with water temperature in intertidal habitats. The subset of studies conducted in a restoration context also showed mostly positive interactions. Twenty-five per cent of all interactions were negative, and these were predominant between plants and infaunal bivalves in intertidal habitats, except sulphide-metabolizing bivalves, which facilitated plant survival. Interactions involving non-native species were also mostly negative. Synthesis and applications. Promoting facilitative interactions through plant–bivalve co-restoration can increase restoration success. The prevalence of positive interactions depends on habitat and environmental conditions such as temperature, and was especially important in subtidal habitats (involving both infaunal and epifaunal bivalves) and in intertidal habitats (involving only epifaunal bivalves). Thus sites and species for co-restoration must be carefully chosen to maximize the chances of success. If done properly, co-restoration could increase initial survival, persistence and resilience of foundation species, and promote the recovery of associated biodiversity and ecosystem services.

    Remote sensing of epibenhtic shellfish using synthetic aperture radar satellite imagery
    Nieuwhof, S. ; Herman, P.M.J. ; Dankers, N.M.J.A. ; Troost, K. ; Wal, D. van der - \ 2015
    Remote Sensing 7 (2015)4. - ISSN 2072-4292 - p. 3710 - 3734.
    bare soil surfaces - mussel beds - wadden sea - ecosystem engineers - intertidal flats - tidal flats - sar data - roughness - classification - moisture
    On intertidal mudflats, reef-building shellfish, like the Pacific oyster and the blue mussel, provide a myriad of ecosystem services. Monitoring intertidal shellfish with high spatiotemporal resolution is important for fisheries, coastal management and ecosystem studies. Here, we explore the potential of X- (TerraSAR-X) and C-band (Radarsat-2) dual-polarized SAR data to map shellfish densities, species and coverage. We investigated two backscatter models (the integral equation model (IEM) and Oh’s model) for inversion possibilities. Surface roughness (vertical roughness RMSz and correlation length L) was measured of bare sediments and shellfish beds, which was then linked to shellfish density, presence and species. Oysters, mussels and bare sediments differed in RMSz, but because the backscatter saturates at relatively low RMSz values, it was not possible to retrieve shellfish density or species composition from X- and C-band SAR. Using a classification based on univariate and multivariate logistic regression of the field and SAR image data, we constructed maps of shellfish presence (Kappa statistics for calibration 0.56–0.74 for dual-polarized SAR), which were compared with independent field surveys of the contours of the beds (Kappa statistics of agreement 0.29–0.53 when using dual-polarized SAR). We conclude that spaceborne SAR allows one to monitor the contours of shellfish-beds (thus, distinguishing shellfish substrates from bare sediment and dispersed single shellfish), but not densities and species. Although spaceborne SAR cannot replace ground surveys entirely, it could very well offer a significant improvement in efficiency.
    A Mixed Modeling Approach to Predict the Effect of Environmental Modification on Species Distributions
    Cozzoli, F. ; Eelkema, M. ; Bouma, T.J. ; Ysebaert, T. ; Escaravage, V. ; Herman, P.M.J. - \ 2014
    PLoS ONE 9 (2014)2. - ISSN 1932-6203
    cockles cerastoderma-edule - natural animal assemblages - quantile regression - lanice-conchilega - body-size - ecosystem engineers - sediment transport - hydrobia-ulvae - abundance - oosterschelde
    Human infrastructures can modify ecosystems, thereby affecting the occurrence and spatial distribution of organisms, as well as ecosystem functionality. Sustainable development requires the ability to predict responses of species to anthropogenic pressures. We investigated the large scale, long term effect of important human alterations of benthic habitats with an integrated approach combining engineering and ecological modelling. We focused our analysis on the Oosterschelde basin (The Netherlands), which was partially embanked by a storm surge barrier (Oosterscheldekering, 1986). We made use of 1) a prognostic (numerical) environmental (hydrodynamic) model and 2) a novel application of quantile regression to Species Distribution Modeling (SDM) to simulate both the realized and potential (habitat suitability) abundance of four macrozoobenthic species: Scoloplos armiger, Peringia ulvae, Cerastoderma edule and Lanice conchilega. The analysis shows that part of the fluctuations in macrozoobenthic biomass stocks during the last decades is related to the effect of the coastal defense infrastructures on the basin morphology and hydrodynamics. The methodological framework we propose is particularly suitable for the analysis of large abundance datasets combined with high-resolution environmental data. Our analysis provides useful information on future changes in ecosystem functionality induced by human activities.
    The drilosphere concept: Fine-scale incorporation of surface residue-derived N and C around natural Lumbricus terrestris burrows
    Andriuzzi, W.S. ; Bolger, T. ; Schmidt, O. - \ 2013
    Soil Biology and Biochemistry 64 (2013). - ISSN 0038-0717 - p. 136 - 138.
    earthworm burrows - laboratory experiment - ecosystem engineers - nitrogen dynamics - soil - carbon - communities - walls
    Anecic (deep-burrowing) earthworms are important for soil biogeochemical functioning, but the fine-scale spatial range at which they incorporate C and N around their burrows (the drilosphere sensu stricto) needs to be investigated under realistic conditions. We conducted a field experiment to delimit spatially the extent to which soil around natural Lumbricus terrestris burrows is influenced biochemically. We placed plant litter dual-labelled with C-13 and N-15 stable isotope tracers on L terrestris burrow openings and we measured residue-derived C-13 and N-15 in thin concentric layers (0-2, 2-4, 4-8 mm) around burrows with or without a resident earthworm. After 45 days, earthworms were significantly enriched in C-13 and N-15 as a result of feeding on the plant litter. At 0-5 cm soil depth, soil N-15 concentrations were significantly higher around occupied than unoccupied burrows, and they were significantly higher in all burrow layers (including 4-8 mm) than in bulk soil (50-75 mm from burrow). This suggests that biochemical drilosphere effects of anecic earthworms, at least in the uppermost portion of the burrow, extend farther than the 2 mm layer assumed traditionally. (C) 2013 Elsevier Ltd. All rights reserved.
    Measuring sedimentation in tidal marshes: a review on methods and their applicability in biogeomorphological studies
    Nolte, S. ; Koppenaal, E.C. ; Esselink, P. ; Dijkema, K.S. ; Schuerch, M. ; Groot, A.V. de; Bakker, J.P. ; Temmerman, S. - \ 2013
    Journal of Coastal Conservation 17 (2013)3. - ISSN 1400-0350 - p. 301 - 325.
    sea-level rise - fallout pb-210 measurements - high-precision measurements - regenerative-dose protocol - rapidly subsiding wetland - barrier salt-marsh - san-francisco bay - fresh-water - ecosystem engineers - accumulation rates
    It is increasingly recognised that interactions between geomorphological and biotic processes control the functioning of many ecosystem types as described e.g. by the ecological theory of ecosystem engineering. Consequently, the need for specific bio-geomorphological research methods is growing recently. Much research on bio-geomorphological processes is done in coastal marshes. These areas provide clear examples of ecosystem engineering as well as other bio-geomorphological processes: Marsh vegetation slows down tidal currents and hence stimulates the process of sedimentation, while vice versa, the sedimentation controls ecological processes like vegetation succession. This review is meant to give insights in the various available methods to measure sedimentation, with special attention to their suitability to quantify bio-geomorphological interactions. The choice of method used to measure sedimentation is important to obtain the correct parameters to understand the biogeomorphology of tidal salt marshes. This review, therefore, aims to be a tool for decision making regarding the processes to be measured and the methods to be used. We, subdivide the methods into those measuring suspended sediment concentration (A), sediment deposition (B), accretion (C) and surface-elevation change (D). With this review, we would like to further encourage interdisciplinary studies in the fields of ecology and geomorphology.
    Greenhouse-gas emissions from soils increased by earthworms
    Lubbers, I.M. ; Groenigen, K.J. van; Fonte, S.J. ; Six, J. ; Brussaard, L. ; Groenigen, J.W. van - \ 2013
    Nature Climate Change 3 (2013). - ISSN 1758-678X - p. 187 - 194.
    nitrous-oxide fluxes - organic-matter dynamics - carbon-dioxide - ecosystem engineers - agricultural intensification - nitrifier denitrification - endogeic earthworms - microbial activity - n2o emission - crop residue
    Earthworms play an essential part in determining the greenhouse-gas balance of soils worldwide, and their influence is expected to grow over the next decades. They are thought to stimulate carbon sequestration in soil aggregates, but also to increase emissions of the main greenhouse gases carbon dioxide and nitrous oxide. Hence, it remains highly controversial whether earthworms predominantly affect soils to act as a net source or sink of greenhouse gases. Here, we provide a quantitative review of the overall effect of earthworms on the soil greenhouse-gas balance. Our results suggest that although earthworms are largely beneficial to soil fertility, they increase net soil greenhouse-gas emissions
    Pontoscolex corethrurus (Annelida: Oligochaeta) indicador de la calidad del suelo en sitios de Eucalyptus grandis (Myrtacea) con manejo tumba y quema
    Uribe, S. ; Huerta, E. ; Geissen, V. ; Mendoza, M.I. ; Godoy, R. ; Jarquin, A. - \ 2012
    Revista biologia tropical = International Journal of Tropical Ecology and Conservation 60 (2012)4. - ISSN 0034-7744 - p. 1543 - 1552.
    tropical tree plantations - organic-matter - ecosystem engineers - secondary forests - nitrogen pools - fire - earthworm - carbon - mexico - water
    La presencia de oligoquetos en los ecosistemas puede indicar fertilidad del suelo, ya que estos organismos transportan, mezclan y entierran los residuos vegetales de la superficie al interior del suelo. Se caracterizó la comunidad de oligoquetos bajo sitios con diferentes periodos de establecimiento y manejo de plantaciones de Eucalyptus grandis, sin vegetación (SV), con cinco años en producción (Euc) y vegetación secundaria con 15 años (Acah) que han pasado por el proceso de tumba y quema en suelos de Acri- sol en Huimanguillo, Tabasco; y se analizaron las propiedades físicoquímicas del suelo (D.A., humedad, textura, pH, Ntot, MO, P, K, CIC). La recolecta de lombrices se realizó al finalizar las lluvias (agosto-octubre 2007). Se muestreó en tres parcelas con seis réplicas en cada una. Se encontró que los suelos tenían pH de 3.0-4.5 en los primeros 30cm de profundidad. Los contenidos de materia orgánica (MO) y nitrógeno total (Ntot) fueron significativamente menores en los sitios SV (6-8% y 0.19-0.22% respectivamente) que en Euc y Acah (MO=9-11%; el Ntot=0.27-0.33%). La especie Pontoscolex corethrurus domino en toda el área, presentando mayores densidades y biomasas en Euc (164.4ind/m2 y 36.8g/m2 respectivamente) y Acah (138.7ind/m2 y 19.1g/m2 respectivamente), mientras que en SV sus poblaciones fueron reducidas en un 80%. Se encontró que el sistema Acah sigue presentando rasgos de un sistema perturbado, al no recuperar fácilmente la diver- sidad de oligoquetos y las concentraciones de nutrientes disponibles en el suelo
    Residue incorporation depth is a controlling factor of earthworm-induced nitrous oxide emissions
    Paul, B.K. ; Lubbers, I.M. ; Groenigen, J.W. van - \ 2012
    Global Change Biology 18 (2012)3. - ISSN 1354-1013 - p. 1141 - 1151.
    organic-matter dynamics - filled pore-space - lumbricus-terrestris - n2o emissions - nitrifier denitrification - ecosystem engineers - microbial activity - n mineralization - crop residues - soil carbon
    Earthworms can increase nitrous oxide (N2O) emissions, particularly in no-tillage systems where earthworms are abundant. Here, we study the effect of residue incorporation depth on earthworm-induced N2O emissions. We hypothesized that cumulative N2O emissions decrease with residue incorporation depth, because (i) increased water filled pore space (WFPS) in deeper soil layers leads to higher denitrification rates as well as more complete denitrification; and (ii) the longer upward diffusion path increases N2O reduction to N2. Two 84-day laboratory mesocosm experiments were conducted. First, we manually incorporated maize (Zea maysL.) residue at different soil depths (incorporation experiment). Second, 13C-enriched maize residue was applied to the soil surface and anecic species Lumbricus terrestris (L.) and epigeic species Lumbricus rubellus (Hoffmeister) were confined to different soil depths (earthworm experiment). Residue incorporation depth affected cumulative N2O emissions in both experiments (P <0.001). In the incorporation experiment, N2O emissions decreased from 4.91 mg N2O–N kg-1 soil (surface application) to 2.71 mg N2O–N kg-1 soil (40–50 cm incorporation). In the earthworm experiment, N2O emissions from L. terrestris decreased from 3.87 mg N2O–N kg-1 soil (confined to 0–10 cm) to 2.01 mg N2O–N kg-1 soil (confined to 0–30 cm). Both experimental setups resulted in dissimilar WFPS profiles that affected N2O dynamics. We also found significant differences in residue C recovery in soil organic matter between L. terrestris (28–41%) and L. rubellus (56%). We conclude that (i) N2O emissions decrease with residue incorporation depth, although this effect was complicated by dissimilar WFPS profiles; and (ii) larger residue C incorporation by L. rubellus than L. terrestris indicates that earthworm species differ in their C stabilization potential. Our findings underline the importance of studying earthworm diversity in the context of greenhouse gas emissions from agro-ecosystems.
    Causes and effects of a highly successful marine invasion: Case-study of the introduced Pacific oyster Crassostrea gigas in continental NW European estuaries
    Troost, K. - \ 2010
    Journal of Sea Research 64 (2010)3. - ISSN 1385-1101 - p. 145 - 165.
    mussel mytilus-edulis - suspension-feeding bivalves - cockles cerastoderma-edule - enemy release hypothesis - northern wadden sea - long-term changes - biological invasions - japanese oyster - ecosystem engineers - filtration-rate
    Since the 1960's, the Pacific oyster Crassostrea gigas has been introduced for mariculture at several locations within NW Europe. The oyster established itself everywhere and expanded rapidly throughout the receiving ecosystems, forming extensive and dense reef structures. It became clear that the Pacific oyster induced major changes in NW European estuaries. This paper reviews the causes of the Pacific oyster's remarkably successful establishment and spread in The Netherlands and neighbouring countries, and includes a comprehensive review of consequences for the receiving communities. Ecosystem engineering by C. gigas and a relative lack of natural enemies in receiving ecosystems are identified as the most important characteristics facilitating the invader's successful establishment and expansion. The Pacific oyster's large filtration capacity and eco-engineering characteristics induced many changes in receiving ecosystems. Different estuaries are affected differently; in the Dutch Oosterschelde estuary expanding stocks saturate the carrying capacity whereas in the Wadden Sea no such problems exist. In general, the Pacific oyster seems to fit well within continental NW European estuarine ecosystems and there is no evidence that the invader outcompetes native bivalves. C. gigas induces changes in plankton composition, habitat heterogeneity and biodiversity, carrying capacity, food webs and parasite life cycles. The case of the Pacific oyster in NW European estuaries is only one example in an increasing series of biological invasions mediated by human activities. This case-study will contribute to further elucidating general mechanisms in marine invasions; invasions that sometimes appear a threat, but can also contribute to ecological complexity.
    Interactions between residue placement and earthworm ecological strategy affect aggregate turnover and N2O dynamics in agricultural soil
    Giannopoulos, G. ; Pulleman, M.M. ; Groenigen, J.W. van - \ 2010
    Soil Biology and Biochemistry 42 (2010)4. - ISSN 0038-0717 - p. 618 - 625.
    nitrous-oxide fluxes - no-tillage agroecosystems - organic-matter dynamics - carbon-dioxide - ecosystem engineers - crop residues - casts - denitrification - management - systems
    Previous laboratory studies using epigeic and anecic earthworms have shown that earthworm activity can considerably increase nitrous oxide (N2O) emissions from crop residues in soils. However, the universality of this effect across earthworm functional groups and its underlying mechanisms remain unclear. The aims of this study were (i) to determine whether earthworms with an endogeic strategy also affect N2O emissions; (ii) to quantify possible interactions with epigeic earthworms; and (iii) to link these effects to earthworm-induced differences in selected soil properties. We initiated a 90-day 15N-tracer mesocosm study with the endogeic earthworm species Aporrectodea caliginosa (Savigny) and the epigeic species Lumbricus rubellus (Hoffmeister). 15N-labeled radish (Raphanus sativus cv. Adagio L.) residue was placed on top or incorporated into the loamy (Fluvaquent) soil. When residue was incorporated, only A. caliginosa significantly (p <0.01) increased cumulative N2O emissions from 1350 to 2223 µg N2O–N kg-1 soil, with a corresponding increase in the turnover rate of macroaggregates. When residue was applied on top, L. rubellus significantly (p <0.001) increased emissions from 524 to 929 µg N2O–N kg-1, and a significant (p <0.05) interaction between the two earthworm species increased emissions to 1397 µg N2O–N kg-1. These effects coincided with an 84% increase in incorporation of residue 15N into the microaggregate fraction by A. caliginosa (p = 0.003) and an 85% increase in incorporation into the macroaggregate fraction by L. rubellus (p = 0.018). Cumulative CO2 fluxes were only significantly increased by earthworm activity (from 473.9 to 593.6 mg CO2–C kg-1 soil; p = 0.037) in the presence of L. rubellus when residue was applied on top. We conclude that earthworm-induced N2O emissions reflect earthworm feeding strategies: epigeic earthworms can increase N2O emissions when residue is applied on top; endogeic earthworms when residue is incorporated into the soil by humans (tillage) or by other earthworm species. The effects of residue placement and earthworm addition are accompanied by changes in aggregate and SOM turnover, possibly controlling carbon, nitrogen and oxygen availability and therefore denitrification. Our results contribute to understanding the important but intricate relations between (functional) soil biodiversity and the soil greenhouse gas balance. Further research should focus on elucidating the links between the observed changes in soil aggregation and controls on denitrification, including the microbial community
    Colonization of PAH-contaminated dredged sediment by earthworms
    Eijsackers, H.J.P. ; Bruggeman, H.J. ; Harmsen, J. ; Kort, T.H. ; Schakel, A. - \ 2009
    Applied Soil Ecology 43 (2009)2-3. - ISSN 0929-1393 - p. 216 - 225.
    artificial soil columns - ecosystem engineers - lumbricus-rubellus - zinc distribution - abandoned fields - new-zealand - availability - succession
    In freshly deposited dredged sediment contaminated with PAHs, we followed the colonization of earthworm species by monthly monitoring over two years. Already five months after deposition the first species, Lumbricus castaneus, appeared, although only temporarily. The first permanent colonizing species was L. rubellus, soon followed by Aporrectodea caliginosa and L. castaneus, and a few months later Eiseniella tetraeda. At the end of the two-year observation period some first few specimen of Allolobophora rosea were present. These earthworm species colonized the deposited sediment apparently in succession. The colonization of each individual species did not show a gradual influx from the bordering dikes at both sides of the deposit, but a fast colonization over the whole width, presumably by surface dispersal, although at low and variable numbers, followed by a gradual increase of population numbers. Modeling the dispersal showed that diffusion was the primary driving factor. Also juvenile earthworms were observed locally in high numbers, so reproduction did occur. Total earthworm numbers in the deposit reached a maximum of 80% of the numbers in the bordering dikes consisting of loamy and clayey soils. Numbers were highest in periods with warm and rainy weather. The appearance of earthworms improved the soil development, stimulated a faster desiccation and aeration of the sediment and may have contributed to the increased degradation of PAHs, especially three- and four-ring PAHs
    Coastal habitat engineers and the biodiversity in marine sediments
    Reise, K. ; Bouma, T.J. ; Olenin, S. ; Ysebaert, T. - \ 2009
    Helgolander Marine Research 63 (2009)1. - ISSN 1438-387X - p. 1 - 2.
    ecosystem engineers
    Impacts of bottom and suspended cultures of mussels Mytilus spp. on the surrounding sedimentary environment and macrobenthic biodiversity
    Ysebaert, T. ; Hart, M. ; Herman, P.M.J. - \ 2009
    Helgolander Marine Research 63 (2009)1. - ISSN 1438-387X - p. 59 - 74.
    control phytoplankton biomass - ecosystem engineers - community structure - edulis l. - nutrient fluxes - benthic communities - coastal sediments - saldanha bay - south-africa - new-zealand
    The aim of this study was to quantify the effect of bottom and suspended mussel cultures, cultured in different physical environments, on the sedimentary environmental conditions and thereby the biodiversity structure of the associated macrofaunal community. We compared two bottom cultures (Limfjorden: microtidal, wind-driven; Oosterschelde: macrotidal) and one suspended culture (Ria de Vigo in an upwelling coastal region). The sedimentary environmental conditions (mud fraction, POC, PON, phosphorus content, chl a breakdown products) were significantly elevated underneath and surrounding bottom and suspended cultures compared to culture-free sediments that were nearby and hydrodynamically similar. The relative change in environmental conditions was more pronounced in the Oosterschelde compared to Limfjorden, most likely due to differences in hydrodynamic forcing and characteristics of the mussel bed. The effect of the suspended cultures in Ria de Vigo on the surrounding sediments was influenced by local topographic and hydrodynamic conditions. The impact of mussels on the benthic community due to biodeposition was clearly seen in the community structure. The species composition changed from species which are typically present in sandy environments to more small opportunistic species, which are typically present in organically enriched sediments. The impact of bottom cultures on the benthic community due to changes in the habitat under the presence of mussels was positive, especially in the Oosterschelde where an increase in the number of epibenthic species was seen. The influence of bottom cultures on the sedimentary environment and on the macrobenthic community seems to be very local. Within the mussel site in Limfjorden, differences were detected between sites where none or almost no mussels were present with sites where mussels were very abundant
    The consequences of changes in abundance of Callianassa subterranea and Amphiura filiformis on sediment erosion at the Frisian Front (south-eastern North Sea)
    Amaro, T.P.F. ; Duineveld, G.C.A. ; Bergman, M.J.N. ; Witbaard, R. ; Scheffer, M. - \ 2007
    Hydrobiologia 589 (2007)1. - ISSN 0018-8158 - p. 273 - 285.
    montagu thalassinidea - ecosystem engineers - resuspension - disturbance - dynamics - growth - echinodermata - ophiuroidea - macrofauna - organisms
    In the early 1990¿s a conspicuous shift took place in the density of two key macrofauna species at the Frisian Front (SE North Sea). The density of the formerly dominant brittlestar Amphiura filiformis showed tenfold reduction and remained low throughout the observation period (1986¿2000). In the same period, the burrowing mud shrimp Callianassa subterranea showed a fourfold increase in density. Since the Frisian Front is a transition area where tidal currents fall just below the erosion threshold of silt and bioturbating mud shrimps can potentially affect the sediment erosion threshold, we examined the effects of the species on sediment erodibility. Two experiments were conducted in laboratory annular flumes. In the first experiment we compared the effects of pre-shift and post-shift combinations of the two species on the erodibility of Frisian Front sediment. The results indicated that the erosion was facilitated by a combination of high densities of C. subterranea and low densities of A. filiformis, representing the situation in the late 1990s. The difference in erodibility was already apparent at velocities equal to the critical near-bed current speed measured at the Frisian Front. In the second experiment the effects of pre- and post-shift densities of A. filiformis on sediment erodibility were compared. This showed that low A. filiformis densities as found in the late 1990¿s facilitate erosion, but the effect is only significant at velocities above the critical near-bed velocity in the field. At the latter velocity, no significant difference in erodibility was found between the two A. filiformis densities. This implies that the difference in turbidity in the first experiment was mainly due to the activity of C. subterranea. The experimental results indicate that resuspension at the Frisian Front may occur more frequently as a result of the shift towards a Callianassa dominated community. More frequent resuspension of bottom sediment, most likely amplified by the climate induced increase of wind strength in the North Sea, may hamper the recovery of the A. filiformis adult population.
    Soil fauna and soil function in the fabric of the food web
    Brussaard, L. ; Pulleman, M.M. ; Ouédraogo, E. ; Mando, A. ; Six, J. - \ 2007
    Pedobiologia 50 (2007)6. - ISSN 0031-4056 - p. 447 - 462.
    organic-matter dynamics - semi-permanent cultivation - sudano-sahelian conditions - habitable pore-space - crusted soil - phosphorus allocation - earthworm activity - microaggregate formation - nitrogen mineralization - ecosystem engineers
    Over the last four decades, spanning David Coleman's career, and in no small measure thanks to him, soil ecologists have made tremendous progress in describing and understanding the overwhelming complexity of biological, biophysical and biochemical interactions in soil. These interactions shape the soil as a habitat for the soil food web and the vegetation and, thereby, regulate the two main life-supporting processes on Planet Earth: production and decomposition. Changes in decomposition and production processes are governed by (human-induced) changes in vegetation composition/cover, the amounts and quality of organic residues and (in)organic fertilizers entering the soil. Such modifications alter the physical environment and the soil biota. Hence, decomposition and production processes cannot be understood and/or manipulated without explicitly addressing the composition and activity of the soil food web. Using a conceptual model, we argue that quantitative understanding of biophysical interactions, in particular those between soil fauna and soil structure, are paramount to understanding biological and biochemical processes in soil and the availability of water and nutrients to plants. The need to increase the efficiency of crop production worldwide, to reverse soil degradation and to increase soil resilience will set the agenda for soil ecologists in the near future
    The use of earthworms in ecological soil classification and assessment concepts
    Rombke, J. ; Jansch, S. ; Didden, W.A.M. - \ 2005
    Ecotoxicology and Environmental Safety 62 (2005)2 sp. iss.. - ISSN 0147-6513 - p. 249 - 265.
    ecosystem engineers - southern sweden - heavy-metals - forest soil - populations - lumbricidae - oligochaeta - organisms - profiles - invertebrates
    Without doubt, earthworms are the most important soil invertebrates in most soils worldwide, in terms of both biomass and activity. Several species are even considered to be ecosystem engineers. Earthworms are also known to influence soil structure, soil chemistry, and, in particular, processes like organic matter decomposition. In addition, standardized sampling methods are available and their taxonomy is well known (even the first PC-aided keys have been developed). For these reasons, earthworms were recognized as a part of ecological classification and assessment schemes early on. However, due to the relatively small number at many sites, they have to be part of a battery approach. By use of examples from The Netherlands (biological indicator of soil quality) and Germany (soil biological site classification), the practicability of the use of earthworms is demonstrated in determining the influence of different anthropogenic land use forms. In these cases, the structure of the earthworm community, as well as their abundance and biomass, were used as endpoints.
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