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Habitat heterogeneity is an important driver of aboveground species diversity but few studies have investigated effects on soil communities. Trees shape their surrounding by both leaf litter and roots generating small scale heterogeneity and potentially governing community patterns of soil organisms. To assess the role of vegetation for the soil fauna, we studied whether tree species (Fagus sylvatica L., Acer pseudoplatanus L., Fraxinus excelsior L., Tilia cordata Mill.), markedly differing in leaf litter quality and root associated mycorrhizal symbionts, affect oribatid mite communities by shaping below- and aboveground resources and habitat complexity and availability. Oribatid mite abundance, species richness, community structure and the proportion of litter living and parthenogenetic individuals were analyzed and related to microbial biomass and the amount of remaining litter mass. Although leaf litter species with higher nutritional values decomposed considerably faster, microbial biomass only slightly differed between leaf litter species. Neither root species nor leaf litter species affected abundance, species richness or community structure of oribatid mites. However, root species had an effect on the proportion of parthenogenetic individuals with increased proportions in the presence of beech roots. Overall, the results suggest that identity and diversity of vegetation via leaf litter or roots are of minor importance for structuring oribatid mite communities of a temperate forest ecosystem., Competing Interests: The authors have declared that no competing interests exist.

Soil food webs are driven by plant-derived carbon (C) entering the soil belowground as rhizodeposits or aboveground via leaf litter, with recent research pointing to a higher importance of the former for driving forest soil food webs. Using natural abundance stable isotopes of wheat (C3 plant) and maize (C4 plant), we followed and quantified the incorporation of shoot residue- and root-derived maize C into the soil animal food web of an arable field for 1 year, thereby disentangling the importance of shoot residue- versus root-derived resources for arable soil food webs. On average, shoot residue-derived resources only contributed less than 12% to soil arthropod body C, while incorporation of root-derived resources averaged 26% after 2 months of maize crop and increased to 32% after 1 year. However, incorporation of root-derived maize C did not consistently increase with time: rather, it increased, decreased or remained constant depending on species. Further, preference of shoot residue- or root-derived resources was also species-specific with about half the species incorporating mainly root-derived C, while only a few species preferentially incorporated shoot residue-derived C, and about 40% incorporated both shoot residue- as well as root-derived C. The results highlight the predominant importance of root-derived resources for arable soil food webs and suggest that shoot residues only form an additional resource of minor importance. Variation in the use of plant-derived C between soil arthropod species suggests that the flux of C through soil food webs of arable systems can only be disentangled by adopting a species-specific approach.

The complexity of soil food webs and the cryptic habitat hamper the analyses of pools, fluxes and turnover rates of carbon (C) in organisms and the insight into their interactions. Stable isotope analysis has been increasingly used to disentangle soil food web structure, yet it has not been applied to quantitatively characterize C dynamics at the level of the entire soil food web., The present study employed 13CO2 pulse labelling to investigate the incorporation of maize root-derived C into major soil compartments and food web players in an arable field for 25 days. Bulk tissue and compound-specific (lipids) C isotope ratios were used to quantify pool sizes and 13C incorporation in bacteria and fungi as primary decomposers, nematodes as key drivers of the microfood web and decomposers and predators among the meso- and macrofauna., About 20% of the C assimilated by maize was transferred to below-ground pools. 13C was predominantly incorporated into rhizosphere micro-organisms rather than in those of the bulk soil. 13C in phospholipid fatty acid biomarkers revealed that root-derived C was incorporated into the soil food web mainly via saprotrophic fungi rather than via bacteria. Only small amounts of 13C were transferred to higher trophic levels, predominantly into fungal-feeding nematodes and macrofauna decomposers., Most importantly, C pool size and 13C incorporation did not match closely. Although the fungal C stock was less than half that of bacteria, C transfers from fungi into higher trophic levels of the fungal energy pathway, that is fungal-feeding nematodes and meso- and macrofauna decomposers, by far exceed that of bacterial C. This challenges previous views on the dominance of bacteria in root C dynamics and suggests saprotrophic fungi to function as major agents channelling recent photoassimilates into the soil food web. [ABSTRACT FROM AUTHOR]

Abstract: The origin and quantity of plant inputs to soil are primary factors controlling the size and structure of the soil microbial community. The present study aimed to elucidate and quantify the carbon (C) flow from both root and shoot litter residues into soil organic, extractable, microbial and fungal C pools. Using the shift in C stable isotope values associated with replacing C3 by C4 plants we followed root- vs. shoot litter-derived C resources into different soil C pools. We established the following treatments: Corn Maize (CM), Fodder Maize (FM), Wheat+maize Litter (WL) and Wheat (W) as reference. The Corn Maize treatment provided root- as well as shoot litter-derived C (without corn cobs) whereas Fodder Maize (FM) provided only root-derived C (aboveground shoot material was removed). Maize shoot litter was applied on the Wheat+maize Litter (WL) plots to trace the incorporation of C4 litter C into soil microorganisms. Soil samples were taken three times per year (summer, autumn, winter) over two growing seasons. Maize-derived C signal was detectable after three to six months in the following pools: soil organic C (Corg), extractable organic C (EOC), microbial biomass (Cmic) and fungal biomass (ergosterol). In spite of the lower amounts of root- than of shoot litter-derived C inputs, similar amounts were incorporated into each of the C pools in the FM and WL treatments, indicating greater importance of the root- than shoot litter-derived resources for the soil microorganisms as a basis for the belowground food web. In the CM plots twice as much maize-derived C was incorporated into the pools. After two years, maize-derived C in the CM treatment contributed 14.1, 24.7, 46.6 and 76.2% to Corg, EOC, Cmic and ergosterol pools, respectively. Fungi incorporated maize-derived C to a greater extent than did total soil microbial biomass. [Copyright &y& Elsevier]