关键词: 根桩, 密度, 损失率, 分解, 萌芽期, 苹果, 氮水平, 氮去向, 新梢旺长期, 土壤氮库盈亏

Abstract: With space as a substitute for time,the changes of the density of stump sapwoods and heartwoods,and the releasing process of major nutrients during the decomposition of Chinese fir stump roots were investigated.The yearly loss rate of the densities of sapwoods and heartwoods was 2.767×10^-2 and 2.255×10^-2 respectively during decomposition.The contents of N and P in sapwoods and roots decreased continually, while those in heartwoods increased during the first stage of decomposition,and then decreased.The K concentration in stump roots decreased remarkably during first two years, and the content of organic substances decreased during the whole decomposition process.The N,P and K concentrations in roots were higher than those in stump sapwoods and heartwoods at the beginning of decomposition,but bet content of organic substance was opposite.

Key words: Stump roots, Density, Loss rate, Decomposition, nitrogen fate, new shoot growing stage, apple tree, soil nitrogen budget, nitrogen level, germination stage