ReCLEAN researchers from EPFL and WSL recently published a new study in Plant and Soil exploring how drought and warming affect nitrogen cycling in different grassland soils. The abstract below summarizes their key findings and highlights why land‑use history plays a crucial role in grassland resilience under climate change. The full article can be found here. 

Abstract

Background and aims

Climate change is expected to intensify drought and heatwaves, with major consequences for nutrient cycling in grasslands. Plant-soil-microbe interactions regulate nitrogen (N) dynamics, yet their responses to simultaneous warming and drought remain unclear, especially across plant species and land management histories.

Methods

We conducted a factorial warming and drought manipulation on six temperate grassland species belonging to three functional groups (grasses, forbs, legumes) grown in soils from intensively (Int) and extensively (Ext) managed grasslands. We quantified N content and biomass production across soil, microbes, roots, and shoots. We inferred fungi:bacteria by microbial C:N, not by direct soil community determination. Results Under control and warming conditions, Int soils supported up to 50% higher plant biomass than Ext soils, but this advantage disappeared under drought, reducing plant biomass by ~ 40%. Warming consistently reduced microbial biomass by up to 30% in both soil types. In contrast, drought decreased microbial biomass in Int soils but increased it by ~ 20% in Ext soils, likely reflecting their more drought-resistant fungal communities. These changes altered N flows: extractable soil N was up to three times higher in Int soils under warming and drought, indicating greater vulnerability to N losses, whereas Ext soils maintained low extractable soil N except under combined stress.

Conclusions

Intensive management boosts plant biomass under mild and warm conditions but increases susceptibility to N loss during climate extremes. Extensive management supports more stable biomass and N cycling. Integrating microbial dynamics and land-use history is essential for predicting grassland resilience and improving N cycling models under global change.

This research is part of the ReCLEAN Joint Initiative co-financed by the ETH Board.