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

AimsLitter 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.MethodsWe 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.ResultsAll 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 & beta;-1,4-glucosidase and & beta;-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 from aboveground litter and promoted the accumulation of calcium and the release of carbon from belowground litter.ConclusionsDifferent mechanisms of above- and belowground litter decomposition under P addition were driven by litter quality and enzyme activity, but moderate P addition increased semiarid grassland litter decomposition, which may contribute to low soil C sequestration.

Automated summary

The study found that the addition of phosphorus fertilizer has different effects on the decomposition of aboveground and belowground litter. Moderate phosphorus addition can promote the decomposition of aboveground litter in semi-arid grasslands, but it inhibits the decomposition of belowground litter. These differences are driven by litter quality and enzyme activity, and moderate phosphorus addition can increase litter decomposition in semi-arid grasslands, but may be detrimental to soil carbon sequestration.