Intensive grassland management and drought amplify pathways of energy flux in soil food webs

Soil food webs contribute significantly to ecosystem energy (carbon) fluxes, but how energy flow through them is affected by both intensification of land management and extreme climatic events, such as drought, is poorly understood. Here, we quantified in situ the energetics and stability of soil food webs under experimental drought across a range grasslands in the United Kingdom with contrasting management intensity. Over the short term of a growing season and a wide range of environmental conditions, drought increased food web energy fluxes and respiration resulting in more unpredictable distribution of fluxes. Intensive grassland management similarly increased energy fluxes and total ecosystem respiration. Our statistical modelling confirmed that the changes observed in soil food web energy fluxes under drought and intensive management trigger an increase in ecosystem respiration mediated by decreased predictability in the distribution of the soil food web energy fluxes. The latter was also linked to reduced population level return time, likely caused by the recovery of metabolically faster components of the food webs such as bacteria. The study thus shed lights on how land use intensification combined with climate change alters pathways of below-ground energy flux and processes that may cause net emissions of C from soil