Tropical land use alters functional diversity of soil food webs and leads to monopolization of the detrital energy channel

Agricultural expansion is among the main threats to biodiversity and functions of tropical ecosystems. Conversion of rainforest into plantations erodes biodiversity with little-explored consequences for food-web structure and energetics of belowground communities, and associated ecosystem functions and services. We used a unique combination of approaches in stable isotope analysis and food web energetics to analyze in a comprehensive way consequences of the conversion of rainforest into plantations on the structure of and channeling of energy through soil animal food webs in Sumatra, Indonesia. Across the 23 animal groups studied, the channeling of energy shifted towards freshly-fixed plant carbon in plantations, indicating fast energy channeling as opposed to slow energy channeling in rainforests. Earthworms as major detritivores stayed unchanged in their trophic niche and monopolized the detrital pathway in plantations. Functional diversity metrics of soil food webs reflected the reduced amount of litter, tree density and species richness in plantations, providing guidelines how to improve the complexity of the structure of and channeling of energy through soil food webs. Our results highlight the strong restructuring of soil food webs with the conversion of rainforest into plantations threatening soil functioning and ecosystem stability in the long term.