Lay summary
Soils in alpine regions are expected to store large amounts of soil carbon because of high carbon concentrations in the topsoil resulting form the temperature limitation of microbial degradation of plant residue inputs. Based on previous findings we suggest that labile carbon with a high sensitivity to temperature is of special importance for the carbon stock in alpine grassland soils, which makes these soils potential CO2 sources under future climate warming. However, site characteristics other than temperature, such as available soil volume or texture, can be limiting at high elevations for both primary productivity and the capacity of soils to store and protect C. The amount of labile C in alpine grassland soils, and the role of various mechanisms of stabilisation and destabilisation accounting for the high temperature sensitivity of soil organic matter decomposition are still poorly understood or even unknown. The aim of this project is to investigate systematically the amount and quality of labile SOM in alpine grasslands in relation to site-specific mean temperature, soil characteristics, and residue quality. This will be done by measuring the corresponding soil and residue quality attributes along four elevation gradients in the Alps differing in geology and texture. A combination of analytical techniques will be used, and calculation of labile SOM turnover times by means of 14C dating will be related to site characteristics and quality of input material to determine the role of the different potential drivers for the dynamics of labile C. We expect that the results of this study will be of great value for modelling the long-term dynamics of soil carbon at alpine sites to project the future behaviour alpine soil carbon stocks.