Effects of N and P additions on leaf litter decomposition in Michelia macclurei woodland

Objective  The effects of external nitrogen and phosphorus on leaf litter decomposition rate and changes in N, P, K contents during the decomposition process were studied in a Michelia macclurei woodland to provide a basis for scientific and rational management of M. macclurei plantations.

Method  Four 5 m×5 m sample plots were set in a M. macclurei woodland of Yunyong forest farm, Guangdong Province. Leaf litters were placed in nylon bags and were sprayed with N, P or N+P respectively. The leaf litter decomposition rate and N, P and K contents were determined every three months.

Result  The decomposition rate of leaf litter was significantly accelerated by N, P and N+P additions. After 24 months of deconposition, the leaf litter decomposition rates of the control, N, P and N+P additions reached 52%, 66%, 78% and 73% respectively. N content of leaf litters of the control, N, P and N+P additions increased by 23%, 33%, 23% and 31% respectively, and was significantly higher than their initial N content, among which N contents of leaf litters treated with N and N+P additions were significantly greater than the control. P content of leaf litters of the control, N, P and N+P additions increased by 7%, 18%, 59% and 46% respectively, and was significantly higher than their initial P content, among which P content of leaf litters treated with P or N+P additions was significantly greater than the control. K content of leaf litters changed irregularly, and that treated with N or N+P additions was significantly smaller than the control, while that treated with P addition was significantly greater than the control. Remaining amounts of N and K of leaf litter in the control were significantly greater than the other treatments, and remaining amount of P treated with N addition was significantly less than the control.

Conclusion  N, P and N+P additions can accelerate leaf litter decomposition in M. macclurei woodland, P addition had the best effect. It is suggested that P fertilizer might be added appropriately in M. macclurei woodlands to promote nutrient cycling.