红花尔基沙地樟子松天然林枯立木特征分析

[目的]了解沙地樟子松天然纯林中枯立木的数量及空间结构特征,探究枯立木形成的原因,为樟子松林的保护和经营提供依据。[方法]在沙地樟子松天然纯林中设置2块1 hm~2的大样地,用全站仪对样地中所有胸径大于5 cm的立木进行定位并进行全面调查;对调查样地的基本特征,枯立木的数量特征及径级分布进行了分析,提出了用于表达林分中枯立木微环境的活立木比的概念,并采用林分空间结构参数一元分布和二元分布分析方法,对枯立木与其最近4株相邻木的关系进行分析。[结果]2块不同密度的樟子松天然纯林下更新幼苗和枯立木数量相差较大,密度较小(样地1)的样地更新幼苗和枯立木较少,而密度较大的样地(样地2)中枯立木达到200棵,林下更新幼苗数量达到15 280株·hm~(-2);樟子松天然纯林样地内枯立木主要以小径级木为主,胸径集中在11 cm以下;样地1枯立木径级连续分布,幅度较窄;样地2中的枯立木径级幅度较宽,但在20 22 cm缺刻,有2株大于23 cm的枯立木;2块样地中枯立木的分布格局均为随机分布,样地1中枯立木周围的4株相邻立木大多为活立木,且胸径较枯立木大;样地2中,只有一半的枯立木周围的最近4株立木为活立木,且有三分之一以上的枯立木胸径不是最小的,枯立木有连续分布的现象。2块样地中枯立木的角尺度-大小比数二元分布特征的差异不明显,而角尺度-活立木比二元分布特征和大小比数-活立木比二元分布特征差异明显,样地1中枯立木的最近4株随机分布于其周围的相邻木为活立木且胸径大于枯立木的比例明显高于样地2,而枯立木最近4株随机分布于其周围的相邻木有枯立木的比例明显小于样地2。[结论]樟子松天然纯林枯立木以小径级林木为主,枯立木的数量与林分密度相关,林木竞争是林木死亡的主要原因,密度过大也会产生病虫害,因此,对天然樟子松纯林要进行适度经营,保持合理密度。

Dead Standing Trees Characteristics Analysis of Pinus sylvestris var. mongolica Natural Forest in Honghuaerji

[Objective] To understand the characteristics and forming of dead standing trees of Pinus sylvestris var. mongolica natural pure forest and provide the basis for the protection and management of P. sylvestris var. mongolica natural pure forest.[Method] Two plots were set up with total station in different density P.sylvestris var. mongolica natural forest with a area of 1 hm² each. All the trees with diameter larger than 5 cm were located and surveyed. The basic characteristics of sample plots, the quantitative characters and class distribution of dead standing trees were analyzed and the concept of living tree ratio was proposed to express the micro environment around dead standing in stand, at the same time, the method of stand spatial structure parameter distribution and bivariate distribution was used to analyze the relationship of the dead standing trees with the nearest 4 adjacent trees.[Result] There was significant difference between amounts of seedlings and dead standing in the P. sylvestris var. mongolica natural forest with different density. The plot 1 was less in stand density, where the amounts of both seedlings and dead standing were less, while that of plot 2 were 15 280 stem·hm^-2 and 200 trees respectively. The dead standing trees of P.sylvestris var. mongolica natural pure forest were mainly small diameter and their diameter was below 11 cm. The diameter classes of plot 1 followed a continuous distribution and the range was narrow; the diameter class range of plot 2 was broad and it was discontinuous in 20~22 cm, there had 2 dead standing trees which diameter was larger than 23 cm. The distribution pattern of dead standing in P. sylvestris var. mongolica natural pure forest followed a random distribution; mostly the 4 adjacent trees around the dead standing trees were living trees and their diameter larger than that of the dead standing trees in plot 1. In half case, all the 4 adjacent trees around dead standing trees were living trees and more than one-third of dead standing trees which DBH were not minimal. The dead standing trees showed the continuous distribution phenomena in plot 2. The difference of dead standing trees bivariate distribution of the uniform angle index and neighbourhood comparison were not obviously and the difference of dead standing tree bivariate distribution of the uniform angle index and mingling, and neighbourhood comparison were obviously. The proportion of 4 adjacent trees randomly distributed around dead standing trees were all living trees and their DBH larger than that of the dead standing trees were significantly higher in plot 1 than in plot 2, however, the proportion of 4 adjacent trees randomly distributed around dead standing trees were dead standing trees were significantly lower in plot 1 than in plot 2.[Conclusion] Mostly, the dead standing trees in P. sylvestris var. mongolica natural pure forest are small diameter trees, the amount of dead standing trees is related to the stand density, and competition is the main reason causing the death of forest trees. When the density of P.sylvestris var. mongolica natural pure forest is too high, it is prone to suffer from pest. Therefore, P. sylvestris var. mongolica natural pure forest need to maintain a reasonable density.