Responses of soil nutrients to vegetation restoration in China

Although vegetation restoration is known to improve soil quality and increase soil microbial activity, its effects on soil nutrients remain largely uncertain because of the complex relationship between plant growth and nutrient cycling. In order to evaluate the responses of soil nutrients to vegetation restoration, we used a standardized procedure to collect 586 and 395 observations for soil total nitrogen (TN) and total phosphorus (TP) in the top 30 cm of soil from 101 published field studies to conduct a meta-analysis in China. Our results revealed that soil TN and TP increased by 47% and 25% following vegetation restoration. Restoration actions made a larger contribution to recovery soil nutrients, and the recovery effects depended on land use history more than restoration approach and age. Vegetation restoration, especially on farmland with broadleaf species, could provide substantial opportunities for TN and TP sequestrations in the top 30 cm of soil. Passive approach (restoration by natural succession) performed better than active approach (restoration with human intervention) for enhancing soil TP content, but the recovery levels of soil TN were insignificantly different between two restoration approaches. Meanwhile, soil TN significantly increased with time after restoration. Soil nutrient dynamics were largely controlled by soil properties and were closely coupled with SOC stock dynamics. The magnitude and direction of the dynamics of soil TN and TP differed among four ecological regions, indicating geographical and climatic heterogeneities had significant impacts on soil nutrient recovery. Dynamics of soil nutrients were significantly influenced by soil properties, geographical locations, and climatic characteristics of the study sites, and these findings could facilitate priority setting and selection of treatment methods for vegetation restoration to enhance soil nutrients.