Differential impacts of degradation on grassland ecosystems in the Tibetan Plateau and the Northern agro-pastoral ecotone: A meta-analysis

PurposeGrassland ecosystems in ecologically fragile areas have experienced severe degradation due to global climate change and intensified human activities. However, responses of grassland ecosystems to degradation in different ecologically fragile areas remain unclear.MethodsWe applied a meta-analysis approach to examine data about vegetation biomass, soil physicochemical properties, and soil microorganisms across different degradation stages in two ecologically fragile areas: Tibetan Plateau (QTP) and Northern Agro-pastoral Ecotone (NAPE).ResultsGrassland degradation leads to reduction in vegetation biomass, and loss of soil carbon (C), nitrogen (N), and phosphorus (P). However, the response of soil potassium (K) to degradation isn't significant in NAPE. Physicochemical properties of soil on QTP exhibit a higher sensitivity to grassland degradation than those in NAPE. Model analysis results suggest mean annual precipitation (MAP), ecosystem type, and soil depth are primary factors contributing to differences in soil physicochemical properties between QTP and NAPE. Within different ecologically fragile areas, changes in enzyme activities are more pronounced, with general decline in soil sucrase (SR) activity, greater sensitivity of urease (URE) to degradation on QTP, and higher sensitivity of polyphenol oxidase (PPO) in NAPE. Further analysis reveals that the main influencing factors of enzyme activity are different in the QTP and the NAPE.ConclusionsIn summary, grassland degradation is a result of the coordinated degradation of vegetation, soil, and microorganisms, displaying variations across different ecologically vulnerable regions and degradation stages. An in-depth investigation of these differences and their driving factors can facilitate the accurate assessment of grassland degradation and formulation of restoration strategies tailored to different regions.