Soils deliver a range of ecosystem services; they store carbon (C) and nitrogen (N), and provide nutrients for plant growth. With the burgeoning world population, pressures on land to produce food, fibre, and biofuel are increasing, alongside an urgent need for a more sustainable agricultural production. The expansion and intensification of agricultural land use has major implications for soils, the biota that live in them, and the ecosystem services that they deliver. Although the abundance and diversity of certain groups of soil organisms has been linked to the delivery of ecosystem services in field experiments, it is not clear whether such relationships also exist on larger scales. Here, we sampled three different agricultural land uses in each of four European countries: low intensity permanent grassland, medium intensity legume rotation, and intensive wheat rotation. We analysed soil properties, food web composition, and C and N losses through leaching and gaseous emissions, and fitted statistical models to these data to assess the importance of spatial distribution of the sites and soil food web properties for explaining ecosystem services.
We found that soil food web structure and biomass was strongly affected by the spatial distribution of sampling sites, and that diversity and biomass of functional groups was generally greater in low intensity grassland than in the other land use types. Specifically, the biomass of the root energy channel, which consists of arbuscular mycorrhizal (AM) fungi, root-associated nematodes, and fungal-feeding fauna, was consistently greater in permanent grassland. Similarly, both the fungal and bacterial energy channel biomass, which consist of fungi and bacteria, and the chain of soil fauna that feed on them, respectively, were greatest in permanent grassland. Importantly, in addition to a strong influence of spatial distribution of sites, we found that individual functional groups of the soil food web were strongly linked to C and N losses, but land use intensity was not. For instance, N leaching decreased with the abundance of AM fungi, and increased with increasing biomass of bacterial-feeding nematodes, whereas soil respiration increased with increasing importance of the fungal energy channel and with earthworm abundance. These findings show that land use impacts on soil food webs are consistent across Europe and that relationships between soil food webs and soil processes are consistent on this scale.