Mineral-associated organic carbon (MAOC) constitutes a major fraction of global soil carbon and is assumed less sensitive to climate than particulate organic carbon (POC) due to protection by minerals. Despite its importance for long-term carbon storage, the response of MAOC to changing climates in drylands, which cover more than 40% of the global land area, remains unexplored. Here we assess topsoil organic carbon fractions across global drylands using a standardized field survey in 326 plots from 25 countries and 6 continents. We find that soil biogeochemistry explained the majority of variation in both MAOC and POC. Both carbon fractions decreased with increases in mean annual temperature and reductions in precipitation, with MAOC responding similarly to POC. Therefore, our results suggest that ongoing climate warming and aridification may result in unforeseen carbon losses across global drylands, and that the protective role of minerals may not dampen these effects.

矿物相关有机碳 (MAOC) 构成全球土壤碳的主要部分，由于受到矿物的保护，人们认为其对气候的敏感度低于颗粒有机碳 (POC)。尽管MAOC对于长期碳储存很重要，但其对占全球陆地面积40%以上的旱地气候变化的反应仍有待探索。在此，我们通过标准化实地调查，对来自 25 个国家和 6 大洲的 326 个地块进行了标准化实地调查，评估了全球旱地的表土有机碳成分。我们发现土壤生物地球化学解释了 MAOC 和 POC 的大部分变化。两种碳含量均随着年平均气温的升高和降水量的减少而减少，MAOC 的响应与 POC 类似。因此，我们的研究结果表明，持续的气候变暖和干旱化可能会导致全球旱地出现不可预见的碳损失，而矿物质的保护作用可能不会减弱这些影响。