不同间伐强度对华北落叶松人工林竞争关系的影响

Analysis of characteristics of north China larch plantations' competitive relationship and its driving factors

通过在3种不同间伐强度的华北落叶松人工林作业区设置样地,利用Hegyi简单竞争指数模型对不同树种对象木以及经营核心目标树的竞争压力量化表达比较,并对抚育间伐对林分竞争特征的改变及驱动作用进行研究。结果表明:间伐能驱动林木竞争特征发生改变,不同间伐强度样地内竞争压力格局呈现不同程度的趋异化;各间伐强度对象木胸径及其所受的竞争压力指数均能被幂函数较好的拟合,其中拟合度排序为中度间伐(李山沟) R2=0.592)>弱度间伐(丁羊沟) R2=0.571)>重度间伐(五叶沟)(R2=0.500);随着间伐强度级别的升高,对象木和目标树受到的竞争压力均减小,间伐对于所受竞争压力偏大的目标树缓释压力的作用更好;不同间伐强度级别目标树所受到的竞争压力差异极显著。不同间伐强度目标树所受竞争压力随径阶升高均呈现下降趋势,小径阶目标树所受的竞争压力较其他径阶相对较大。

A sample plot was established in the Larix principis-rupprechtii plantation with three different levels thinning intensities.We used a Hegyi simple competition index to quantify competition between different tree species.Also,the changes in the competitive features of trees that were caused by intermediate cutting and driving role were studied.The findings indicated that intermediate cutting could accelerate changes in trees'competitive features.In the sample plot with the different thinning intensities,In our experimental plot,competitive responses varied between trees in the different the thinning intensity treatments.Diameter at breast height(DBH)and competitive pressure index of each thinning intensity could be greatly fitting by power function the degree fitting was ranked as:moderate thinning(Lishangou)(R2=0.592)>weak thinning(Dingyanggou)(R2=0.571)>severe thinning(Wuyegou)(R2=0.500).The competitive pressure of object trees and target trees were reduced with an increase in thinning intensity.Further,intermediate cutting relieved pressure from target trees that were experiencing high competitive pressures.The difference in competitive pressure between target trees under different thinning intensities was extremely statistically significant.The competitve pressures than target trees experienced under the various thinning intensities decreased with an increase in diameter class.The competitive pressure suffered by target trees in the small diameter class was higher than in the other diameter classes.