Long-Term Anthropogenic Disturbances Exacerbate Soil Organic Carbon Loss in Hyperarid Desert Ecosystems

Anthropogenic disturbance is an important driver factor of global change, greatly affects the soil organic carbon (SOC) storage. However, the long-term impacts of anthropogenic disturbance on SOC stability in hyperarid deserts remain poorly understood. Through a 16-year anthropogenic disturbance experiment, we evaluated SOC dynamics in hyper-arid desert ecosystems under five treatments: no-disturbance (CK), spring harvest, autumn harvest, fire, and irrigation (simulating artificial flooding). We analyzed SOC composition, sources, and drivers across six soil layers (0-5, 5-15, 15-30, 30-60, 60-100, and 100-150 cm). Results revealed that disturbance ways and particulate organic carbon (POC) dominated SOC variations in topsoil (0-15 cm), while microbial-derived C and plant-derived C controlled subsoil (100-150 cm) dynamics. With the increase of soil depth, the concentrations of SOC, POC, microbial-derived C, and plant-derived C continuously decreased. All disturbance treatments significantly reduced SOC pools compared to CK, with average decreases of 13.2% (SOC), 16.3% (POC), 41.1% (mineral-associated organic carbon, MAOC), 4.2% (plant-derived C), and 16.2% (microbial-derived C). Rises in POC/MAOC (+46.2%), β-1,4-glucosidase/SOC (+21.6%), and cellobiohydrolase/SOC (+13.6%) signify disturbance-induced SOC stability reduction. Autumn harvest and irrigation disturbances caused the largest SOC losses, with SOC reductions of 20% and 21%, respectively, compared to CK. Mechanistically, plant-derived C depletion correlated with reduced plant C inputs, while microbial-derived C decline was linked to altered mineral properties (exchangeable Ca, noncrystalline oxides and free oxides) and microbial properties (enzymes, microbial biomass, fungi and bacteria). Overall, our findings demonstrate that 16 years of anthropogenic disturbance exacerbated SOC loss in hyper-arid deserts, particularly in topsoil. However, the subsoil organic C pool (> 100 cm) mediated by microbial- and plant-derived C also warrants further attention. This study provides the first empirical evidence quantifying depth-specific SOC vulnerability in hyperarid deserts under sustained human pressures, highlighting the critical need to integrate subsurface C dynamics into desert ecosystem management strategies.