Influence of the climate extreme events recorded in 2022 and 2023 on carbon and nitrogen forms in alpine tundra

Alpine tundra ecosystems are highly sensitive to climate change, particularly due to their dependence on the duration and timing of snow cover. This study investigated the effects of the climate extreme years 2022 and 2023 on carbon (C) and nitrogen (N) forms in two alpine tundra communities: snowbed (SB) and Carex curvula (CC), located at high elevation in the North-West (NW) Italian Alps. During these years, both sites experienced exceptionally low snow cover duration and elevated mean soil temperature during the snow-free season. Dissolved organic carbon (DOC) concentrations significantly increased by +65% in SB and +42% in CC compared to 2016–2021, likely reflecting enhanced microbial decomposition of organic matter. In contrast, soil ammonium and nitrate levels showed no significant changes, indicating differential responses between C and N processes. These findings suggest that DOC is a sensitive (early) indicator of climate-induced shifts in soil functioning. Given the critical role of alpine tundra in global C cycling, understanding DOC dynamics under climate extreme events is crucial to predict future ecosystem feedback to global change.