Soil food web properties explain ecosystem services across European land use systems

Abstract

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.

Keywords: modeling; nitrogen; soil fauna; soil microbes.

Fig. 1.

Fitted relationships between ecosystem services and soil food web properties. Variables that were included in the models but not shown in the graphs (Tables 1 and 2) were kept constant at their mean value in the dataset. (A) Potential N mineralization explained by standardized biomass of the bacterial energy channel. (B) Total N leached explained by AMF biomass and biomass of bacterivorous nematodes. (C) N₂O production explained by biomass of flagellates. (D) CO₂ production explained by F/B channel ratio and earthworm biomass. (E) CH₄ production explained by F/B ratio and bacterial biomass (relationship shown is for intensive wheat rotation and permanent grassland) (extensive rotation CH₄ production increases with 0.17 mg m⁻² d⁻¹ are shown in Table 2). (F) DOC leached from soil explained by fungivorous collembolans and bacterivorous nematodes (relationship shown is for intensive wheat rotation and extensive rotation) (permanent grassland DOC leaching increases with 1,317 mg m⁻² as shown in Table 2).