Consequences of the multichannel structure of soil food webs on ecosystem functioning
2023
Quévreux, P. | Jabot, Franck | Unité Mixte de Recherche sur l'Ecosystème Prairial - UMR (UREP) ; VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Campus France through the PHC PROCOPE project number 49348UL | IDEX-ISITE initiative 16-IDEX-0001 (CAP 20-25) | ANR-20-CE32-0004,ASTEC,Un modèle stoechiométrique d'écosystème pour relier biodiversité et fonctionnement des écosystèmes dans les agro-écosystèmes(2020)
Soil fauna significantly contributes to litter decomposition and carbon cycle but it has been neglected in most soil ecosystem models in which biological activity is limited to microbial activity. Soil food webs have been empirically described as the addition of a micro-food web relying on microbial production and of a macro-food web relying on detritivorous invertebrates, which contrasts with the linear producer-consumer-top predator view of food webs usually considered in food web theory. To understand the consequences of such a structure on ecosystem functioning, we built two versions of a dynamic bioenergetic model harbouring either a multichannel structure, in which different resources and consumers generate distinct energy channels, or a purely size-dependent trophic structure seen here as null model. We parametrised these models based on published literature and compared their outputs to independent worldwide soil ecosystem data. We found that the multichannel structure successfully predicts the empirical relationship between body sizes and trophic levels in soils. It also correctly predicts the biomass distribution among the main invertebrate trophic groups, although it underestimates the microbial biomass. Both models predict similar carbon flows. They also predict a major contribution of microbivores (e.g. protists and nematodes) to the total ecosystem respiration contrary to previous model-based estimations. This underlines the potentially high impact of microfauna on the carbon cycle in spite of its low abundance. Our model represents a milestone to link the trophic dynamics of soil fauna to ecosystem functioning and biogeochemical cycles.
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