Vulnerability of mineral-associated soil organic carbon to climate across global drylands

International audienceMineral-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

Vulnerability of mineral-associated soil organic carbon to climate across global drylands

DATA AVAILABILITY : The data associated with this study are publicly available via figshare (https://doi.org/10.6084/m9.figshare.24678891) (ref. 68).EXTENDED DATA : EXTENDED DATA FIG. 1. Locations of the 326 plots surveyed across global drylands. Locations are shown as red circles on a global aridity (1 – annual precipitation/potential evapotranspiration) map for drylands (areas with aridity > 0.35), on a less arid-to-more arid color scale. EXTENDED DATA FIG. 2. Effects of climate on particulate organic C (POC) and mineral-associated organic C (MAOC) in dryland soils with organic C contents below and above the median. EXTENDED DATA FIG. 3. Importance of climate, biotic factors, and soil biogeochemistry in random forest models of particulate organic carbon C (POC) and mineral-associated organic carbon C (MAOC) in global drylands. EXTENDED DATA FIG. 4. Effects of soil biogeochemistry on particulate organic C (POC) and mineral-associated organic C (MAOC) contents across global dryland soils. EXTENDED DATA TABLE 1. Summary statistics of the numeric predictors and covariates used to examine the response of particulate organic carbon (POC) and mineral-associated (MAOC) contents to climate across global drylands. EXTENDED DATA TABLE 2. Categorical covariates used to examine the response of particulate organic carbon (POC) and mineral-associated (MAOC) contents to climate in global drylands.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.The European Research Council, the Spanish Ministry of Science and Innovation, Generalitat Valenciana, the University of Alicante, the King Abdullah University of Science and Technology (KAUST), the KAUST Climate and Livability Initiative, the Hermon Slade Foundation, a María Zambrano fellowship funded by the Ministry of Universities and European Union-Next Generation plan, the US National Science Foundation, the Taylor Family–Asia Foundation Endowed Chair in Ecology and Conservation Biology, a Ramón y Cajal grant from the Spanish Ministry of Science, the German Research Foundation, German Federal Government for Science and Education, the Hans Merensky Foundation, FCT—Fundação para a Ciência e a Tecnologia, AdaptForGrazing project, LTsER Montado platform, and NASA.https://www.nature.com/nclimate/2025-01-30hj2024BiochemistryGeneticsMicrobiology and Plant PathologyPlant Production and Soil ScienceSDG-13:Climate actionSDG-15:Life on lan