LAUSR

Abstract Soil carbon plays a key role in agriculture and ecosystem. Semi-arid regions cover many parts of China, holding a carbon pool that should not be ignored. Thus, systematic studies of the carbon distribution and variation in semi-arid regions are necessary. In this study, we comprehensively analyzed the factors that influence the distribution and variation in soil carbon covering area over 0.92 × 106 km2. Results indicated that the average values of soil organic carbon density (at the soil sampling depth of 0–20 cm) in the study area were 0.58–4.50 kg/m2. Soil organic carbon density (SOCD) was clearly related with climate conditions (e.g., temperature and precipitation), soil properties (e.g., pH and soil texture) and human activities. The results revealed a significant negative relationship between SOCD and temperature. Meanwhile, SOCD showed positive relationship with precipitation. Correlation analysis also demonstrated a negative correlation between SOCD and soil pH, but positively associated with soil Al:Si ratio. Land utilization and fertilization would also affect SOCD in the regions. Upon comparing the current data with that of the 1980s, soil organic carbon storage presented a remarkable increasing trend with 2.55 Tg in these studied regions due to land use change. These findings would provide evidences and insights for the future land managements of semi-arid regions of China in the context of global climate change.