宁夏六盘山区辽东栎林的空间分布及林分特征

基于2005年森林资源一类清查数据,分析了六盘山区辽东栎林分结构和空间分布特征。结果表明:辽东栎林在六盘山主要分布于海拔1 900-2 300 m范围内,坡度为20-35°的半阴坡、半阳坡和阴坡上,与山杨林的分布生境相近。现有的辽东栎林多为幼龄林,平均林龄30 a,林分密度较大,平均1 046株·hm^-2,树木平均高度7.8 m,平均胸径12.4 cm。胸径5-10 cm的辽东栎株数占50％以上,平均木材蓄积量仅为 39.9 m³·hm^-2。随着海拔升高、坡位从坡上部到坡下部,坡向从半阴坡到半阳坡,林分密度增大,平均树高和胸径增加,这主要是因为沿此梯度林龄在增加,而且随着年龄的增加,辽东栎林的平均胸径以0.8 cm·a^-1的速度增大,作为主要先锋伴生树种的山杨在林内的比重则下降,说明六盘山区的现有辽东栎林正处于正向演替阶段,更趋稳定。建议对辽东栎林采取近自然林业的管理方式,减少不利的人工干预,加速培养近自然森林。

The Characteristics of Stand Structure and Spatial Distribution of Quercus liaotungensis Forests in Liupan Mts.

In this study, the characteristics of stand structure and spatial distribution of Quercus liaotungensis forest in Liupan Mts. were analyzed based on the forestry resources inventory data collected in 2005. It was showed that Quercus liaotungensis forest is mainly distributed in the sites with an elevation of 1 900-2 300 m, an aspect of semi-shady, semi-sunny and shady slope, and a slope gradient of 20-35°. The sites with Quercus liaotungensis forest were very close with those occupied by Populus davidiana forests. The existing stands of Quercus liaotungensis were young forests, with an age of 30 years in average. The stand density was large with the average of 1 046 trees·hm^-2. The mean tree height was 7.8 m, and the mean DBH was 12.4 cm. The trees with a DBH of 5-10 cm accounted for more than 50% of the total. With the increasing elevation, the change of aspect from semi-shady to shady and to semi-sunny slope, the variation of slope position from upper part to lower part, both the density and DBH and height of trees increased. These are mainly due to the forest age increase. As key accompanying pioneer tree species in the Quercus liaotungensis forest, the amount of Populus davidiana decreased when increasing forest age. This demonstrated that the existing Quercus liaotungensis forest is in the process of progressive succession. Thus, the close-to-nature management was suggested to promote the right development of current Quercus liaotungensis forests to the direction of close-to-nature forest stand.