Intensive management disrupts belowground multi-trophic resources transfers in response to drought

Abstract

Modification of soil food webs by historical land management may alter the response of ecosystem processes to climate extremes, but empirical support for this is limited and the mechanisms involved remain unclear. Here, we quantified how historical grassland management modifies transfers of recent photosynthate and soil nitrogen through plants and soil food web in response to drought, using in situ 13C and 15N pulse-labelling in paired intensively and extensively managed fields. We show that intensive management decreased plant carbon capture, its transfer through key components of food webs and soil respiration compared to extensive management. Drought only affected carbon transfer pathways in intensively managed grasslands, by increasing plant C assimilation but decreasing its transfer to plant roots, bacteria and Collembola. However, drought lowered the reduction of added nitrate to nitrous oxide in extensively managed grassland only. Our findings indicate that intensive management disrupts fluxes of recent photosynthates belowground, which impaired resistance of this process in response to drought. By contrast, extensive grassland management provides a greater potential to buffer impacts to drought by promoting the transfer of recent photosynthate belowground. Our work highlights that capture and rapid transfer of photosynthate through multitrophic networks is a key process for maintaining grassland resilience to drought.