Mineral-associated carbon stability weakens the soil organic carbon positive feedback to warming

Soil organic carbon (SOC) pool is the largest terrestrial carbon pool, playing a pivotal role in carbon-climate feedback. However, the response of different SOC fractions to warming remains unclear. Here, categorizing SOC into particulate and mineral-associated organic carbon (POC and MAOC) with physical fractionation, we investigated the responses of POC and MAOC content and temperature sensitivity (Q₁₀) to warming, and explored the underlying mechanisms through a 3-year <i>in situ</i> warming experiment (open-top chambers, +1.6°C) in abandoned croplands across China (latitude: 22.33-46.58°N). Our results indicated that on average, POC content remained unchanged while MAOC content significantly increased under warming. Belowground biomass and microbial necromass carbon were the important influencing factors for POC and MAOC content, respectively. POC Q₁₀slightly increased while MAOC Q₁₀ remained unchanged under warming. The Q₁₀ of POC and MAOC was influenced by POC carbon quality and mineral protection, respectively. Due to the low Q₁₀, the increase in MAOC content in abandoned croplands would weaken the positive feedback of SOC to climate warming.