Nutrient addition and warming alter the soil phosphorus cycle in grasslands: A global meta-analysis

Purpose Grasslands are the most extensive vegetation type in the terrestrial ecosystem and have an important role in the soil phosphorus (P) cycle. Many nutrient addition and warming experiments have been conducted in grasslands; however, the global pattern of nutrient addition and experimental warming impacts on soil P cycle is unclear. Methods We conducted a meta-analysis of 68 publications to synthesize the mechanisms underlying global grassland ecosystem responses to nutrient addition and experimental warming. Results Our analysis indicated that nitrogen (N) addition reduced microbial biomass P (− 11.2%) but increased litter P concentration (+ 15.5%) and available P (+ 14.2%). Experimental warming reduced microbial biomass P (− 10.5%) and available P (− 6.7%) but increased litter P concentration (+ 46.2%). P addition increased available P (+ 222.3%) and microbial biomass P (+ 98.1%). The available P response to nutrient addition and experimental warming was more sensitive in temperate grasslands than in alpine grasslands. The responses of soil total and available P to nutrient addition depended on environmental conditions such as air temperature and soil pH. Conclusion Our results suggest that N addition may promote P mineralization and possibly stimulate the transformation of refractory or resistant forms of soil inorganic P, whereas experimental warming accelerates the P cycle by regulating plant acquisition and enzyme activity. Environmental factors (e.g., temperature, precipitation, pH) affect the soil P response to nutrient addition by altering microbial and enzymatic activities. It is crucial to understand the dynamic changes in soil microbial and enzyme activities to predict the P cycle in grassland soils in the future.