Search

We studied abundance, diversity, and composition of soil invertebrates along snowmelt gradients to generally understand how soil animal communities are responding to life conditions across snowbeds along a west–east transect of the European Alps and to create a reference inventory for future investigations of climate change effects on snowbed habitats. We extracted microarthropods (collembolans, oribatid mites) and macroinvertebrates (spiders, beetles, insect larvae) from soil cores taken from three sections along the snowmelt gradient: high (early snowmelt), middle, and low (late snowmelt) sections. Linear models showed no correlations between either soil conditions or time of snowmelt and densities of soil animals. A small, though statistically significant, variation in the generally high soil organic matter and sand contents and high porosity of snowbed soils seems to have no effect on soil invertebrates. Species found along the snowmelt gradient were in similar shares generalist and specialist species. Microarthropod community composition in general was driven by soil porosity and soil organic matter content; for macroinvertebrate community composition we found no specific driver. We conclude that invertebrate species assemblages in snowbeds are rather similar in the European Alps. [ABSTRACT FROM AUTHOR]

Soil macro-invertebrates play an important role in the formation and functioning of soils, which makes them indispensable for all terrestrial ecosystems, including high alpine soils. However, in the latter, knowledge on species identity, diversity, and functionality of macro-invertebrate soil communities is scarce. Here, we address this knowledge gap by investigating the structural and functional composition of soil macro-invertebrate communities in high alpine sites of the European Alps that differ in sheep grazing intensity (low, medium, and high). Abundance data were combined with the analysis of natural variations in stable isotope ratios ( 13 C/ 12 C, 15 N/ 14 N) of food sources and soil animals, allowing insight into the trophic structure of the decomposer community. The presence of sheep significantly increased the abundance of Nematocera, but reduced the abundance of most other taxa. Diplopoda were found exclusively at the low elevation site with almost no sheep grazing, while Diptera larvae increased in numbers at higher elevation sites. Lumbricidae species were abundant at all sites except the highest site, which was intensively grazed by sheep and also used as a resting place. In contrast, trophic relations were not affected by sheep grazing intensity, four trophic groups were clearly distinguished, pointing to a relatively simple food web structure: (1) primary decomposers, (2) secondary decomposers and dung feeders, (3) root and fungal feeders, and (4) predators. We suggest that the shallow soils with high organic matter do not allow the formation of more complex food webs. [ABSTRACT FROM AUTHOR]

Abstract: Faecal pellets of macro-decomposers form an important component of upper soil layers. It is, however, not yet specifically known which species’ faecal pellets are important in the process of humus and soil formation. Here we present a novel approach, based on the detection of short DNA fragments, to species-specifically assign faecal pellets to their detritivorous producers. Using diagnostic polymerase chain reaction (PCR), DNA of the two millipede species Cylindroiulus fulviceps and C. meinerti, abundant macro-decomposers on European alpine pastureland, could be detected in their faecal pellets. Although in both species detection was possible up to 5 days post-defecation (no longer intervals were tested), detection rates were significantly higher in C. fulviceps (81.3%) than in Cylindroiulus meinerti (60.9%) in repetitive PCRs. Employing a binomial mixture model, the probability that the producer’s DNA was present in a faecal sample which tested negative in five subsequent PCRs was estimated as 22.0% for C. fulviceps and 41.9% for C. meinerti, suggesting to adopt a flexible stopping rule for assaying this type of samples. This proof-of-concept study demonstrates that the molecular assignment of faecal pellets to their macro-invertebrate producers is possible, offering a new approach to examine the role of decomposer faecal pellets in soil formation and functioning as well as to complement molecular profiling of faunal communities. [Copyright &y& Elsevier]

Abstract: We tested whether experimental summer drought affects the transfer of recently photosynthesized carbon from plants to soil mesofauna in a subalpine meadow. From day one after 13CO2 pulse-labelling of the plant canopy, roots, collembolans and mites were enriched in δ13C in control, but not in drought plots. However, as the difference in δ13C between roots and soil animals was not affected by the drought treatment, we conclude that drought affects the tight linkage between photosynthesis and soil mesofauna primarily via functional responses of plants rather than via changes in the mesofauna. [Copyright &y& Elsevier]