Phosphorus fertilization affects litter quality and enzyme activity in a semiarid grassland

Aims Litter decomposition affects soil organic carbon storage, and nutrient addition alters exogenous nutrient availability in soil, thereby affecting the endogenous nutrient concentration and extracellular enzyme activity in litter. However, how above- and belowground litter decomposition responds to nutrient addition is not fully understood. Methods We conducted a 7-yr field experiment with 5 levels (0, 1, 2.5, 5, and 12.5 g P m -2 yr -1 ) of phosphorus fertilization (P). Starting in the 6th year, we determine litter decomposition, nutrient elements, and enzyme activity to explore the response mechanisms of above- and belowground litter decomposition to P addition. Results All levels of P addition increased the rate of aboveground litter decomposition, but only 2.5 g P m −2 yr −1 increased that of belowground litter. P addition increased the litter initial P and Mn contents, while decreased the C/P and N/P ratios of aboveground litter, which stimulated the activities of β-1,4-glucosidase and β-1,4-N-acetylglucosaminidase, thereby increasing the aboveground litter decomposition rate. The belowground litter decomposition was mainly inhibited by lignin content, and 2.5 g P m −2 yr −1 addition significantly decreased lignin content and increased the phenol oxidase activity, thereby accelerating the decomposition. P addition promoted the accumulation of P and the release of cellulose in aboveground litter and promoted the accumulation of calcium and the release of carbon in belowground litter. Conclusions The different mechanisms of above- and belowground litter decomposition under P addition were driven by litter quality and enzyme activity, facilitating the understanding of the soil and plant interaction mechanisms in grassland ecosystems.