倒木干扰对红松针阔混交林空间结构的影响1）

以红松针阔混交林样地（200 m×140 m）为研究区,采用角尺度、混交度和大小比数3个指标对倒木出现前后的林分空间结构进行量化分析。结果表明：样地内倒木比例占7．15％,且中等径木居多,倒木数量与该树种立木多度呈极显著正相关（ r＝0．816,P＝0）;从倒木存在形式看,倒木数量为连根拔起＞根倒＞干折,倒木数量的差异与立地条件、树木生长特性密切相关;倒木使林分整体的混交度增大,角尺度和大小比数减小,但由非参数检验得知差异并不显著;倒木对不同树种空间结构的影响呈现出一定规律性,树种平均混交度的增量与其倒木比例呈极显著正相关（ r＝0．715,P＝0．002）,平均大小比数的增量与该树种倒木平均胸径呈显著正相关（r＝0．579,P＝00．24）,与倒木和立木的平均胸径之比呈极显著正相关（ r＝0．806,P＝0）。

Effects of Fallen Trees on Spatial Structure of Coniferous-broad Leaved Korean pine Mixed Forest

With a 200 m×140 m sample plot of coniferous-broad leaved Korean pine mixed forest, we measured three indexes in-cluding uniform angle index, mingling and neighborhood comparison to quantitatively analyze the change of spatial structure in the forest before and after tree falling down.There were 7.15%of standing trees falling in the plot, and the medium-thick ones were in the majority.There was a very significant positive correlation between the number of different specie fall-en trees and their relative abundance ( r=0.816, P=0) .The number of fallen trees in descending order was uprooting, root-break, and stem-break, and the difference mainly resulted from site condition and characteristics of tree growth.Fall-ing trees increased the mingling and reduced the uniform angle index and neighborhood comparison in the forest, but there was no significant variation statistically.There was a high significant positive correlation between different specie increment of mean mingling and the percentage of fallen trees ( r=0.715, P=0.002) .Different specie increment of mean neighbor-hood had a significant positive correlation with mean DBH ( r=0.579, P=0.024) of the fallen tree, and had a high signifi-cantly positive correlation with the fallen-to-stand ratio of mean DBH ( r=0.806, P=0) .