Long-term warming drives mineral-associated organic carbon accumulation on the Tibetan Plateau

Global warming affects both plant growth and soil microbial decomposition, creating uncertainty for the storage and persistence of soil organic carbon (SOC) stock. Limited decomposition rates often characterise cold alpine ecosystems. Yet, warming may increase their microbial activity, affecting SOC sequestration. Here, we present findings from a 14-year field warming study carried out in an alpine meadow on the Qinghai-Tibetan Plateau. Warming significantly increased mineral-associated organic carbon (MAOC) by 11% in topsoil and 6% in subsoil—primarily through an increase in iron/aluminium-bound organic carbon (Fe/Al-OC) in topsoil and calcium-bound organic carbon (Ca-OC) in subsoil. On the contrary, warming did not affect particulate organic carbon (POC). MAOC content was strongly positively correlated with soil fungal biomass and fungal necromass carbon, highlighting the role of fungal-derived carbon inputs. Our results reveal distinctly different responses of SOC pools to long-term warming and underscore the importance of organo-mineral interactions in shaping SOC dynamics in cold ecosystems under climate change. Read the free Plain Language Summary for this article on the Journal blog.