Effects Of Different Intensity Thinning On Litter Decomposition In Chinese Fir Plantations

Four kinds of plots, light intensity thinning(about 30%, the number of trees intensity, the same below), medium intensity thinning(about 50%), high intensity thinning(about 70%) and a control check, were set up in the 25-year-old Chinese fir plantations of Cunninghamia lanceolata(Lamb.)Hook. after 7 years thinning in Lishui District, Nanjing. Study the dynamic changes of litter decomposition rate, substrate quality, microbial communities and enzyme activities with litter bags. Seek for the most appropriate intensity of thinning, to accelerate litter decomposition rate, which can promote nutrient cycling in Chinese fir plantation, and provide a theoretical basis for the reasonable forest management. The results show that:1.Thinning has significant effects on litter decomposition rate in Chinese fir plantations. MIT and LIT can accelerate the decomposition rate, also slow down the litter excessive accumulation and improve soil nutrient input. HIT reduces litter decomposition rate, block the nutrient returning and usage.2.In this study, C/N ratio is the best factor to reflect the litter decomposition rate. Thinning caused litter substrate quality differences, such as carbon and nitrogen content, C/N ratio, lignin /N ratio in litter.3.Different thinning intensity has significant effects on urease, cellulose and sucrose activities in litter layer. MIT can significantly imcrease the enzyme activity in the process of litter decomposition, which promotes the decomposition and nutrient cycling and speeding up the flow of forest litter material.4.Thinning can change the composition and structure of microbial communities in litter of the Chinese fir plantations, It influenced by the interaction effect between of seasons and thinning. The change of carbon source used by microbial, lead to the differences in microbial communities’ functions and structure in different thinning intensities, most significantly in spring and winter.5.The main factors affecting litter decomposition rate are temperature, sucrase and cellulase activities. And the carbon content, nitrogen content and C/N ratio in litter control the microbial functional diversity during the litter decomposition. Through changing the temperature and enzyme activity, thinning changes litter decomposition rate in Chinese fir plantations, and then changes the forest nutrient cycling.