Persistance de la matière organique dans les sols d'altitude : stabilisation et vulnérabilité climatiques : De puits de carbone à source de gaz à effet de serre : les sols alpins, bombe à retardement climatique

Soil organic matter plays a central role in biogeochemical processes within the critical zone, underpinning terrestrial fertility while storing large amounts of carbon and nitrogen. In high-elevation soils, organic matter stocks are typically high due to low temperatures that slow microbial mineralization, extending mean residence time of soil organic matter and enhancing its stabilization. However, mountain regions are warming at an accelerated pace, threatening the stability of these stocks and potentially triggering the release of greenhouse gases (GHGs) such as CO₂ and N₂O. This study investigates the mechanisms governing organic matter persistence in mountain soils through a multi-scale approach (in vitro, in situ, in natura, and in silico) to anticipate their response to key climate change drivers: rising temperatures, phenological shifts, and reduced snow cover duration. Findings confirm that organic matter in high-elevation soils is highly vulnerable to climate warming, primarily due to its strong dependence on climatic stabilization. Increased microbial activity under warmer conditions not only accelerates mineralization but also alters C and N cycling, with potential for increased greenhouse gases emissions. These results, relevant beyond the study region, offer critical insights for refining climate feedback models and forecasting ecological responses in high-elevation ecosystems but also at high latitudes. They also underscore the need to integrate soil processes more explicitly into global change scenarios and species distribution models.