Nitrogen‐Fixing Woody Plants Sequester More Soil Mineral‐Associated Carbon and Lose Less Particulate Carbon Than Herbs Post Vegetation Restoration

Dividing soil organic carbon (SOC) into particulate (POC) and mineral‐associated organic carbon (MAOC) is crucial for understanding the formation, persistence, and functions of soil carbon. However, current understanding of the dynamics of new and old carbon in POC and MAOC following vegetation restoration remains unclear. Here, we investigated the dynamics of new and old carbon in POC and MAOC using stable 13 C isotope techniques, and analyzed their regulatory mechanisms. Forests, shrublands and grasslands all showed higher POC than croplands ( p < 0.05), while MAOC increased significantly only in forests and shrublands, both dominated by nitrogen‐fixing woody plants. There was no significant difference in the accumulation rate of new POC among restored land uses, but more loss of old POC in grasslands resulted in the lowest net accumulation rate (0.14 Mg ha −1 year −1 ). The accumulation rate (0.12 Mg ha −1 year −1 ) and net accumulation rate (0.06 Mg ha −1 year −1 ) of new MAOC in grasslands were lower than those in forests (0.25 and 0.16 Mg ha −1 year −1 ) and shrublands (0.29 and 0.21 Mg ha −1 year −1 ). The accumulation of new carbon increased with carbon input quantity and quality. Improvements in soil structure and the shift of microbial communities from K‐strategists to r‐strategists favored soil carbon stabilization. Collectively, in terms of soil carbon sequestration, nitrogen‐fixing woody plants are more suitable than herbs for vegetation restoration, as they sequester more MAOC and lose less POC. These findings will help deepen our understanding of soil carbon sequestration following vegetation restoration.