Effects of snow pack reduction and drought on litter decomposition in subalpine grassland communities

Abstract

In subalpine grasslands, litter decomposition controls soil nutrient availability and is highly sensitive to increasing intensity and frequency of extreme climate events, potentially impacting grasslands diversity and functioning. Here, we assessed the effects of early snowmelt and summer drought on decomposition, and how these were modulated by agricultural management. In a common garden, conservative and exploitative assembled communities were submitted for two years to combined snow removal and drought, and to cutting and fertilization. We measured decomposition rates of standard and native leaf material from each plant communities on their respective soils. We observed relatively weak climatic stress effects on decomposition rates. Management increased decomposition rates and remaining litter N contents through leaf quality improvement rather than changed soil biotic activity. Climate events impacted the decomposer community and limited litter N immobilization in conservative communities. Less recalcitrant litter of exploitative species facilitated decomposition and counterbalanced the negative effects of climate stress. Our results suggest that drought and earlier snowmelt could decrease N availability in subalpine grasslands due to reduced litter biomass and decomposition. In the long-term climate change may shift subalpine grasslands towards more conservative plant composition and lower soil fertility.