关键词: 北方针叶林, 人为火, 逻辑斯蒂回归, 空间分析

Abstract: As a vital carbon sink in forest ecosystems, fine roots (≤2 mm in diameter) with short life span and high metabolic activity are sensitive to environmental changes. It is important to understand the mechanisms of fine root decomposition and nutrient release in response to forest management practices. To examine the effects of forest management on fine root decomposition, we employed three selective cutting managements, including shrub cutting (SC), nonPinus massoniana cutting (NPMC) and dominant P. massoniana cutting (DPMC), and a control with no cutting (NC) in P. massonianaplantation in the Three Gorges Reservoir area in 2013. After three years of forest management, litterbags filled with P. massoniana fine roots were buried in soil under different treatments. Mass losses and nutrient concentrations of fine roots were measured every three months. After one year decomposition, forest managements had significant effects on soil temperature and humidity, soil nutrients and soil microbial biomass carbon and nitrogen, but had no significant effect on the fine root decomposition rate. There were no significant correlations between fine root decomposition rate and environmental factors. During decomposition, C residual rates gradually decreased, showing a pattern of DPMC>SC>NC>NPMC. Nitrogen was immobilized first and then released, while P followed a mode of release immobilizationrelease. The release rate of P was significantly reduced by selective cutting management. In all, the changes of environmental factors caused by forest management practices are not the dominant factors driving fine root decomposition of P. massoniana.The quality of fine root initialmatrix is the decisive factor. Selective cutting management can increase C release but decrease N and P release rate.

Key words: boreal forest, human-caused fire, Logistic regression, spatial analysis.