The Aridity Threshold of Soil Organic Carbon Density Along the Climate Aridity Gradient in the Alpine Ecosystem of the Qinghai‐Tibetan Plateau

Soil organic carbon density (SOCD) is a key indicator for evaluating the stability of soil carbon pools, especially in alpine ecosystems that are sensitive to climate change. However, research on the response of SOCD to different aridity gradients is still limited. Therefore, we conducted extensive sampling along different aridity gradients of the Qinghai‐Tibetan Plateau to study how SOCD varies with aridity gradients and how environmental factors drive changes in SOCD under different aridity gradients. The study has found that the SOCD at depths of 0–100 cm on the Qinghai‐Tibetan Plateau ranges from 0.39 to 78.12 kg C m −2 . Meanwhile, the SOCD is higher in the more humid southeastern region than in the more arid northwestern region. Topography, climate, and vegetation factors jointly regulate the distribution of SOCD. The SOCD shows a nonlinear variation trend and decreases with the increase of aridity; the key aridity threshold is 0.66. The altitude, aridity, mean annual temperature (MAT), and normalized vegetation index (NDVI) are the main drivers of SOCD below this threshold (low aridity gradient). Moreover, the SOCD is primarily affected by the NDVI and MAT above this threshold (high aridity gradient). The above research results emphasize the differences in SOCD across aridity gradients, suggesting that it may be possible to mitigate the negative impact of aridification on soil organic carbon by increasing vegetation coverage in areas with high and low aridity gradients.