The effects of degradation on alpine grassland resilience: A study based on meta-analysis data

Alpine grasslands on the Qinghai-Tibet Plateau (QTP) provide irreplaceable ecosystem services to local and global communities. However, intensive human activities have caused severe grassland degradation during recent decades. Due to the harsh environment, these degraded grasslands recover slowly or may be irrecoverable after they degenerate to a certain stage. To understand the changes in the resilience of alpine grassland on the QTP after degradation, we evaluated the resilience indexes of the plant, soil and plant-soil systems of grasslands at different degradation stages based on an integrated assessment system and data extracted from 53 published studies in this region. The results showed that,with grassland degradation, most plant indicators including plant height, aboveground biomass, belowground biomass, Cyperaceae, Gramineae, and soil indicators including silt, clay, soil organic carbon, soil total nitrogen, available nitrogen, available phosphorus, available potassium, and soil water content gradually decreased; soil variables including sand, bulk density, and soil temperature showed an increasing trend; and Margalef richness index, Shannon-Wiener index, Pielou evenness index, and forbs first increased and then decreased. The resilience indexes of the plant, soil and plant-soil systems all displayed an obvious downward trend with the increase of degradation degree, which indicates that reduction of grassland resilience is the coordinated degeneration of vegetation and soil. To restore degraded grassland, we should focus on improving both soil and vegetation status to enhance the resilience of grassland ecosystems.