Dynamics and drivers of primary productivity along a 40‐year grazing exclusion chronosequence in a typical steppe of Inner Mongolia

Grazing exclusion has emerged as an effective measure to restore forage production and soil carbon sequestration of degraded grasslands. However, the appropriate duration of grazing exclusion for restoring these ecosystem functions remains largely unclear. To fill this knowledge gap, we monitored aboveground net primary productivity (ANPP), belowground net primary productivity (BNPP), belowground biomass (BGB), soil carbon content, and other relevant soil properties along a grazing exclusion chronosequence spanning 0, 7, 15, 20, and 40 years in a typical steppe of Inner Mongolia, China. Our findings reveal that both ANPP and BNPP reached their maximum after 7 years of grazing exclusion and maintained a high level from 7 to 20 years, but significantly declined after 40 years of grazing exclusion. In contrast, BGB and soil carbon content reached their maximum after 20 years of grazing exclusion. Furthermore, the increase of grazing exclusion duration and the decrease of soil pH increased the density and individual biomass of grasses, rather than forbs, thereby increased community ANPP and BNPP. These findings emphasizes that the restoration of different ecosystem functions may require varying durations of grazing exclusion. Our study provides new information for institutional stakeholders to improve grazing exclusion policy in degraded typical steppe.