大兴安岭北部林区林火干扰强度对兴安落叶松群落影响研究

研究大兴安岭北部林区不同强度林火干扰对兴安落叶松群落的影响。通过对兴安落叶松群落乔木层、下木层和草本层植被的调查与分析发现：乔木层的多样性几乎没有变化．林火干扰对兴安落叶松林的平均胸径、平均树高和平均枝下高均有明显的影响，并且随着干扰强度的增强呈增长趋势．按照干扰强度由轻到重（即轻度、中轻度、中重度、重度）．平均胸径分别增加了5％（差异不显著）、24％、56％、87％；平均树高分别增加了8％、25％、56％、87％；平均枝下高分别增加了28％、48％、60％、93％；林火干扰对下木层植物的多样性指数随着林火干扰强度的增加，呈先上升再下降的趋势。在中轻度干扰下．达到最大值。之后随着林火干扰强度的增加缓慢下降．但均大于未干扰时的多样性干扰强度对该层植物的丰富度指数和均匀度指数的影响也是呈先上升，在中轻度时达到最大值，之后下降的趋势．中轻度干扰下的植物种类较未干扰时增加40％．重度干扰减少40％。草本层植物多样性指数随林火于扰强度的变化与下木层植物刚好相反：在中轻度时下降到最小值，之后随干扰强度的增加而上升。对于丰富度指数，中轻度于扰和重度干扰对其影响明显：中轻度干扰时植物种类增加了42％．重度干扰时减少了42％。均匀度指数只在中轻度干扰时显著降低．总之．一定间隔期的中轻度火干扰有益于兴安落叶松群落。

The Effect of Fire Severity on the Larix gmelini Community in North Great Xing'an Mountains

The effect of the different fire severity on the Larix gmelinii community is studied. Based on the analysis of the vegetation in the layers of trees, under-canopy and herb in the Larix gmelinii community under the different fire severity, the result indicated that the diversity index of the tree layer hardly changed. The average diameter at breast height, the average height and its lowest branches rised apparently after the fire:the average diameter at breast height increased 5%,24%,56%,87%; the average height 8%,25%,56%, 87%; the average height of the lowest branches 28%,48%,60%,93% respectively from low to intensive severity; the diversity, richness and evenness indexes of the herb under-canopy showed a rise-fall pattern. In this layer the diversity index of the vegetation arrived at the peak value under low-medium severity and then fell slowly but all of them were higher than that in undisturbed areas. Under low-medium severity the species of vegetation increased 40%. And under intensive severity decreased 40%. The trend of three indexes observed in the herb layer was just reverse to those in the under-canopy layer; under low-medium severity the species of herb layer vegetation increased 42% which decrease 42% under intensive severity. In a word the fire of low-medium severity with certain interval will be beneficial to the Larix gmelinii community.