Abstract
We investigated the impact of regional conditions and land-use intensity on eight selected arthropod taxa of Mesostigmata (Parasitidae), Oribatida (3 species), Collembola (1 species), Chilopoda (2 species) and Diplopoda (1 species) sampled in differently managed permanent grasslands of three German study regions. By jointly analyzing changes in abundance and trophic behavior (measured as natural variation in 15N/14N and 13C/12C ratios) we intended to develop a framework for evaluating the impact of local and regional conditions on the ecosystem services delivered by soil animals (mainly decomposition- and predation-related services). The investigated taxa could be assorted to three major groups: (1) numerical response only, (2) numerical and trophic response and (3) trophic response only. Since the combination of taxa assembled in the individual groups does not correspond to any of the conventional soil ecological classification systems, this grouping offers a new approach for analyzing soil communities. The complementing consideration of both the direction of the numerical response and the type of the trophic response (change of the basal food source vs. trophic level shift vs. variations in isotopic niches) provided a differential insight into the effect of management and geographic differences on soil arthropods. It could be shown that the effect of land-use on the abundance of detritivorous microarthropods varies among regions, but does not induce any changes in feeding behavior. Our findings on Parasitidae indicate that carnivorous microarthropods exert substantial predation pressure on soil mesofauna and may be quite resistant to environmental changes due to high trophic flexibility. If conditions are favorable, centipedes may reach comparatively high densities in permanent grasslands and could be very important for controlling belowground pests. Concerning millipedes, isotopic signatures suggest that some species could exert a substantial disservice by feeding on roots over a wide range of land-use intensities and regional conditions. We conclude that the many consistent and significant effects found in our study support our contention that the combined analysis of numerical and trophic responses provides a promising framework for designing spatially explicit models that quantify the impact of human interventions on the delivery of ecosystem services by the soil fauna.
Highlights
Edaphic animals affect a wide range of ecological processes and soil-related ecosystem services (Brussaard, 1997; Heemsbergen et al, 2004; de Vries et al, 2013) with detritivores inter alia contributing to plant nutrition, carbon turnover, detoxification, and soil quality (Wardle et al, 2004; Nielsen et al, 2011)
The abundance of three out of four detritivorous mesofauna species (Eupelops occultus, Tectocepheus velatus, and Isotoma viridis) was significantly related to land-use intensity, but the strength and direction of this relationship depended on the study region (Table 2)
The abundance of the collembolan species I. viridis increased with land-use intensity (Figure 1C), while that of the oribatid mite E. occultus decreased with an increase of land-use intensity (Figure 1A)
Summary
Edaphic animals affect a wide range of ecological processes and soil-related ecosystem services (Brussaard, 1997; Heemsbergen et al, 2004; de Vries et al, 2013) with detritivores inter alia contributing to plant nutrition, carbon turnover, detoxification, and soil quality (Wardle et al, 2004; Nielsen et al, 2011). Spatially explicit predictions of such services and their magnitude are difficult, since the contribution of soil animals to ecosystem processes may considerably differ among sites due to local or regional differences in the abundance, the functional role or both of the species involved. The interplay between regional conditions and local land-use is likely to modify the contribution of edaphic animals to ecosystem services. It remains unknown, to what extent such changes manifest themselves through numerical and/or functional responses of the soil fauna to large- and small-scale differences in environmental conditions (Barrios, 2007; Crotty et al, 2014)
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