小陇山锐齿栎天然林结构动态分析

目的]为了解锐齿栎天然林群落动态变化过程。方法]采用每木定位监测样地重复观测的方法,对甘肃小陇山林区百花林场王安沟营林区内的锐齿栎天然林进行研究,从树种组成及多样性结构、径级结构、空间结构等几方面分析了锐齿栎天然林群落的结构动态特征。结果]表明:2次调查群落树种组成和优势树种的重要值排序变化不大,有2个稀少种退出群落,死亡林木40株,死亡率8.3%;群落乔木层的物种丰富度和树种空间多样性下降,优势树种的集中性变大,物种个体数目分配的均匀程度下降。林分径级结构由典型的反"J"型分布变化为左偏的单峰状曲线;群落的空间结构没有发生显著变化,林木分布格局仍为随机分布,中林层和上林层林木个体增加,垂直结构更趋复杂;树种隔离程度下降,建群种锐齿栎的优势度增强,膀胱果、白桦和青榨槭种群的优势度下降。结论]锐齿栎天然林群落组成和结构变化是一个复杂和缓慢的过程,6年间仅发生了一些微小的波动。

Structure Dynamic of Quercus aliena var. acuteserrata Natural Forest on Xiaolongshan

Xiaolongshan forest area of the West Qinling Mountains, China, is an important natural forest system in northwest China. The zonal vegetation type of the area is pine-oak mixed forest. The structure of a Quercus aliena var. acuteserrata natural forest established in 2007 in the Wangangou forest range, Baihua Forest Farm, Xiaolongshan forest area, Gansu Province, was reexamined in 2013 via fixed sampling of individual trees and their positions. The dynamic characteristics of the community were analyzed in terms of species composition, diversity, and stand structure. No significant changes were observed in either community species composition or the order of importance values of dominant tree species. However, two rare species had exited the community, and 40 trees had died, resulting in a mortality rate of 8.3%. The species richness of overstory layer, tree species spatial diversity, and the number of individual species in the community all decreased from 2007 to 2013, whereas the concentration of dominant tree species increased. The spatial structure of the stand did not change significantly, the distribution pattern of trees in the community remained random, and the abundance of individuals in the intermediate and upper layers increased. The vertical structure of the community a typical reverse J-shaped distribution to a single peak curve skewed to the left. The spatial structure of became more complex, and the segregation of tree species decreased. The dominance of the constructive species, Q. var. acuteserrata, and its main associated tree species increased, whereas the dominance of pioneer tree species decreased.