Energy Fluxes and Functions of Soil Food Webs Depend on Land-Use Choices in North-Patagonia Andean Landscapes

Abstract

The consequences of land-use change for soil fauna communities and soil functionality are hard to quantify and poorly understood. Energy fluxes present a quantitative framework to link soil food webs to ecosystem functions. Here, we examined topsoil fauna in a forest-agriculture matrix in North Patagonia, Argentina, to assess the variation of soil food webs functioning across a gradient of land-use intensification. The sampled plots included native forests, grazed ecosystems (cattle and sheep), and crops (perennial and seasonal). In each plot, we assessed soil fauna communities to model soil animal food webs and estimate energy fluxes and associated trophic functions to assess multifunctionality. Our findings revealed up to three times higher total fauna biomass and energy flux in most land-use systems compared to native forests, while the number of interactions and the energetic inequality (unevenness in resource consumption) did not follow a linear trend. Soil organic matter (SOM) consumption increased up to four times with sheep grazing and horticulture, litter transformation decreased around 60% with horticulture, and microbivory doubled in most land uses. Carbon sequestration, as a ratio between SOM consumption and faeces production, was around 70% higher under sheep grazing and horticulture. Herbivory and predation showed different patterns between seasons, but a 67% reduced top-down herbivore control potential was found under sheep grazing. Overall, the responses did not follow a linear intensification gradient. Native and cattle-grazed forests showed lower energy fluxes but more balanced ecosystem functions. Perennial crops hosted more interactions and a similar potential for carbon storage and herbivore control than forests. Under sheep grazing and horticulture, increases in soil fauna biomass and energy flux mainly reflected in higher SOM consumption. Our research emphasises the relevance of land-use decisions for soil food-web structure and related functions, contributing to identifying land uses associated with high ecosystem functionality and livelihoods sustainability.

Keywords: Land-use change, food webs, energy fluxes, ecosystem functions, macrofauna, mesofauna