Abstract:

The litter bag method was used to investigate the differences in dynamic weight loss rate, leaf litter decomposition rate and substrate quality of a Larix principis-rupprechtii plantation under different mountain site conditions in Beijing. The results showed that elevation and slope were two main factors in determining the site difference (Site class Ⅲ, Ⅳ). There were two peaks for leaf weight loss rate under two site conditions during the one-year observation. T_0.5 in Ⅲ and Ⅳ was 2.57 and 2.67 years, and t_0.95 was 11.09 and 11.24 years, respectively. The average annual weight loss rate, the decomposition rate and initial inorganic nutrient content in Ⅲ were higher than in Ⅳ. Compared with Ⅳ, the average C/N value and lignin content in Ⅲ were more benefit to the decomposition of coniferous litter. The initial inorganic nutrient content of litter was not significantly different between two site conditions, while the initial content of C and lignin existed significant (P<0.05) difference. Correlation analysis showed that there were significantly negative correlations between litter decomposition rate and total carbon, C/N ratio and litter layer thickness, and the correlation coefficients were -0.735, -0.569 and -0.758, respectively. Substrate quality indexes indicated that the forest density of 1 675 tree·hm^-2 was most favorable to litter decomposition in Ⅲsite condition, while the density in 1 300 tree·hm^-2 was the most beneficial to decomposition of coniferous litter in the Ⅳ site condition.

Key words: Larix principis-rupprechtii, plantation, litteri, site conditions, decomposition rate