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International audience; Conventional, intensively managed coffee plantations are currently facing environmental challenges. The use of shade trees and the organic management of coffee crops are welcome alternatives, aiming to reduce synthetic inputs and restore soil biological balance. However, little is known about the impacts of the different types of shade tree species on soil functioning and fauna. In this paper, we assess soil nutrient availability and food web structure on a 17-year old experimental coffee plantation in Turrialba in Costa Rica. Three shade types (unshaded coffee, shaded with Terminalia amazonia, and shaded with Erythrina poepiggiana) combined with two management practices (organic and conventional) were evaluated. Total C and N, inorganic N and Olsen P content, soil pH, global soil fertility, and nematode and microarthropod communities were measured in the top 10 cm soil layer, with the objective of determining how shade tree species impact the soil food web and soil C, N and P cycling under different types of management. We noted a decrease in soil inorganic N content and nematode density under conventional management (respectively -47% and -91% compared to organic management), which suggested an important biological imbalance, possibly caused by the lack of organic amendment. Under conventional management, soil nutrient availability and fauna densities were higher under shade, regardless of the shade tree species. Under organic management, only soils under E. poeppigiana, a heavily pruned. N-2 -fixing species, had increased nutrient availability and fauna density, while T amazonia shade had a null or negative impact. The effects of coffee management and shade type on soil nutrient availability were mirrored by changes in soil food web structure. Higher fertility was recorded in soil with balanced food webs. These results emphasize the importance of the choice of shade tree species for soil functions in low input systems, more so than in fertilized systems

International audience; Plant litter is the main carbon (C) source of belowground communities, influencing the functioning of terrestrial ecosystems. In cultivated systems, litter varies quantitatively (restitution or exportation of aerial plant parts) and qualitatively (crop rotation) throughout the year. The effects of litter quantity and quality on the soil biota structure and their relative contributions at different trophic levels have rarely been simultaneously assessed in agricultural soils. To evaluate the role of litter quality and quantity on soil food webs, we incorporated two litter types (labile or recalcitrant) and two litter quantities (low or high) in a long-term experimental site studying the impact of different cultural practices in Northern France. After 7 months, we measured the litter mass loss, enzymatic activities (hydrolytic and oxidative), nitrogen (N) content and biomass of the soil biota: microorganisms, nematodes, Acari, Collembola, earthworms and macro-arthropods. Litter quantity and quality had distinct effects on the structure and functions of soil communities. Doubling the quantity of added litter caused deep changes in the composition of detritivorous fauna by promoting the largest-sized group of detritivores (anecic earthworms) to the detriment of the smaller-sized groups (Collembola), which in turn led to higher litter consumption for a similar amount of soil biota biomass and hydrolytic enzyme activities after seven months of decomposition. In contrast, low litter quality stimulated the fungal energy channel, with an increase in the relative proportion of fungi, fungal feeding nematodes and euedaphic and hemiedaphic collembolans. This food web was characterized by a shift towards nitrogen acquisition that decreased the C:N ratio of enzymatic activities. Litter management is a central factor to consider for influencing ecosystem services such as soil fertility and nutrient cycling through the promotion of specific functional groups in soil.