Abstract:

Purpose: Understanding the rate of litter decomposition and the pattern of nutrient element release will help to detect the ecosystem function of nutrient cycling under different models of selective cutting and provide scientific basis for sustainable management for ecological public welfare forests. Methods: In the Three Gorges Reservoir area, one no-cutting treatment (retaining the forest state without any cutting) and three selective cutting treatments including shrubs cutting (removed the shrub and hard wood saplings except the regenerated Pinus massoniana saplings), non-P. massoniana cutting (removal of all DBH ≥ 4 cm trees except P. massoniana, with a selective cutting intensity of 15%) and dominant P. massoniana cutting (removal of P. massoniana trees with the DBH bigger than the mean level, with a selective cutting intensity of 70%) were conducted in P. massoniana dominated forests. Decomposition in-situ method was used to study litter decomposition rate and nutrient release rate of P. massoniana leaves under four treatments and detect the dominant factors affecting the litter decomposition. Results: The litter decomposition rate of P. massoniana was 0.304, 0.397, 0.311 and 0.315 g·g^-1a^-1 in no-cutting, shrubs cutting, non-P. massoniana cutting and dominant P. massoniana cutting stands respectively. Compared to the control of no-cutting, litter decomposition rate increased 30.59% under shrubs cutting, 2.30% under non-P. massoniana cutting and 3.62% dominant P. massoniana cutting treatment. During the decomposition of leaf litter, a similar trend of nutrients release was observed under four selective cutting models. C concentration decreased significantly in the first 6 months and then slightly fluctuated, N concentration decreased at the initial decomposition stage and then continuously increased, while P concentration was constant and stable. Interaction of selective cutting measures and decomposition time had significant effect on the release rate of C and N, while had no significant effect on P concentration. The decomposition rates were positively correlated to the initial N concentration and N/P of the fallen leaves but not related to soil temperature or soil humidity. Conclusion: In the short term, the decomposition rate of P. massoniana leaves was increased by all three selective cutting treatments compared to the no-cutting treatment. That means of selective cutting method can avoid nutrients to excessively accumulate in litter layer and promote them return into soil. In the future, selective cutting in slight or moderate degree will be a good way to build reasonable stand structure and facilitate nutrient cycling in coniferous plantation.

Key words: selective cutting, litter, decomposition rate, nutrient release, Pinus massoniana