5. Conclusion
Our result showed that N, P and NP addition could significantly affect the decomposition of litter matter, and P addition could alleviate the inhibitory effect of litter decomposition by high N concentration. N and P had an interactive effect on the decomposition of litter matter. The lignin remaining rate of litter was slightly enriched in the late stage of decomposition, which was most obvious in high N treatment, while the cellulose remaining rate decreased continuously with decomposition time. Litter C, N and P basically showed a continuous release pattern, with the strongest promoting effect in NP treatment. All additive treatments significantly increased soil invertase, cellulase, polyphenol oxidase, urease, and phosphatase activities, which were generally higher in the NP treatment than the other treatments. The rate of litter decomposition was significantly influenced by nutrient content as well as soil enzyme activity, where cellulose content and invertase activity may be a key factor controlling the rate of litter decomposition.