Early spring snowmelt and summer droughts strongly impair the resilience of bacterial community and N cycling functions in a subalpine grassland ecosystem

Subalpine grasslands support biodiversity, agriculture, and tourism but their resilience to extreme climatic events is challenged accelerating vulnerability tipping points. Microbial communities, central in ecosystem functioning, are usually considered more resistant highly resilient albeit functional redundancy strong selection by local harsh conditions. This study explored the soil microbial responses upon recurrent spring-summer droughts associated with early snowmelt subalpine mesocosms set-up at Lautaret Pass (French Alps). Potential respiration, nitrification denitrification activities were monitored over a period of two growing seasons along quantification related gene abundances. Impacts simulated drought quantified assess resistance recovery. Results revealed that had low short-term adverse impact on bacterial total respiration supporting hypothesized high resilience, i.e. ability recover. Nitrification abundances corresponding guilds showed relatively summer declined response snowmelt. was paralleled recovery denitrifying communities from all extremes, except where nitrifiers collapsed. Denitrification respective groups faced applied stresses reduction abundance activity. Although, consequently lower denitrifiers' competition for nitrate may be positive plant biomass production, warnings exist when considering potential leaching as well risks greenhouses gases emission such N2O these ecosystems.