The response of degraded grasslands to different types of restoration measures in western China: A Meta-analysis

Grasslands are an important component of terrestrial ecosystems. Restoring degraded grasslands is critical for the stability of ecosystem structure and function. The effects of different types of restoration measures on degraded grasslands were examined by meta-analysis. Restoration measures included natural restoration, artificial supplementary, and ecological engineering. This study investigated the effects of various restoration measures on the Shannon-Wiener index, aboveground biomass, underground biomass, and soil organic carbon. The spatial and temporal variability of the effectiveness of restoration measures was determined. The results revealed that the effects of restoration measures on degraded grasslands varied. Natural restoration significantly increased aboveground and underground biomass; artificial supplementary restoration significantly increased above-ground and under-ground biomass but significantly decreased species diversity; and ecological engineering had no significant effect on any of the indices. The positive effects of natural restoration were more evident, and its suitability was higher. Additionally, the suitability of the restoration measures changed over time. Artificial supplementary measures were more effective within five years of restoration, whereas natural restoration was effective after more than five years. Moreover, ecological engineering, artificial supplementary, and natural restoration exhibited positive effects on heavily, moderately, and lightly degraded grasslands, respectively. The suitability of restoration measures was also influenced by spatial characteristics. The restoration measures suitable for semi-humid, semi-arid and arid areas were artificial supplementary, natural restoration, and ecological engineering, respectively. Therefore, grassland restoration measures should be selected according to spatio-temporal characteristics.