Abstract:

Seedlings of five hardwood tree species, Castanopsis lamontii, Cyclobalanopsis myrsinaefolia, Castanopsis fissa, Castanopsis kawakamii, and Castanopsis sclerophylla were separately planted under 25-year-old Masson Pine plantation. After sixteen years following planting, the amount, nutrient contents and turnover time of forest litter were investigated in the above five types of mixed uneven-aged stands and pure Masson Pine forest. Results revealed that annual litterfall in the five mixed stands were 6 149.1, 7 533.2, 6 741.1, 7 151.5 and 8 041.7 kg·hm^-2 respectively, but only 3 442.8 kg·hm^-2 in pure Masson Pine stand. Binomial patterns was found for seasonal dynamics of litter in the mixed stands. The first peak occurred from February to April, the second occurred in August or September. Leaves account for 50%～71% of the total litter, branches 6%～26%, barks 9%～19%, fruits about 1%, and other components 5%～17%. In the mixed stands, 50%～58% of the total litterfall came from Masson Pine trees, 42%～50% from the respective hardwood trees, with significant difference existing between their litter composition. Nutrient concentrations of litterfall were different, with N ranging from 3.25～12.98、0.37～6.55、0.24～0.97、12.77～35.40 and My to 2.35～6.10 g·kg^-1. Total return of the five nutrient elements via litterfall for the six stands consistently decreased in the order: Ca>N>Mg>K>P. From annual litterfall the total return of five nutrient elements were 238.05, 213.77, 223.93, 289.90 and 304.12 kg·hm^-2 respectively, for the five mixed communities, and 142.01 kg·hm^-2 for pure Masson Pine stand. Litter accumulation in the forest floor in the five mixed stands were up to (8 448.0,) (15 565.8,) (11 993.7,) 12 718.6, and 6 974.2 kg·hm^-2 respectively, and 5 020.0 kg·hm^-2 for pure Masson Pine forest, with layer L making up of 47.2%, 59.6%, 51.3%, 61.0%, 85.4%, and 86.3% of the total respectively, averaged 61.7%. Significant differences in nutrient concentrations existed between forest communities and litter components, but the elements consistently revealed the same trend, decreasing in the order: Ca>N>Mg or K>P. Based on comparative analysis on litter accumulation and annual litterfall, the turnover time of litter in the six stands was estimated to be 1.15, 0.76, 1.42, 0.97, 1.17, 0.84 and 1.52 years respectively. Branches had longer turnover time than leafves. The branches and leaf from Masson Pine generally exhibited greater turnover time than that from the corresponding hardwood species interplanted under the pine canopy.

Key words: mixed forest of Masson Pine and hardwood, forest litter, forest floor, nutrient content, litter turnover time