Effects of vegetation restoration on soil organic carbon in the Loess Plateau: A meta-analysis

Vegetation restoration is one of the most effective ways to increase soil organic carbon (SOC). After the implementation of vegetation restoration policies such as the Grain-for-Green Program, which has increased regional vegetation coverage. However, the impact of land use, vegetation types, restoration time, and topographic and meteorological factors on SOC remains unclear. Therefore, this study examined the effect of vegetation restoration on SOC in the Loess Plateau through a meta-analysis of 520 sample data collected from 60 research papers. The results showed that vegetation restoration in the Loess Plateau significantly increased SOC by 29.40%. Restoration time was the most important factor affecting the SOC after revegetation. Land use type was an important factor that influenced SOC; the most significant impact on SOC was found when the previous land use type was abandoned land and the current land use type was woodland. Different vegetation types resulted in different SOC as follows: Fagaceae > Salicaceae > Pinaceae > Leguminosae. Broad-leaved forests had significantly higher SOC than that of coniferous forests. Non-nitrogen-fixing plants increased SOC significantly compared to nitrogen-fixing plants. SOC decreased in 0-5 years after vegetation restoration, and then increased with the increase of restoration years. Especially, the soil carbon sequestration effect of vegetation has been significantly improved after 10 years of restoration.