两种采伐方式对马尾松人工林林分空间结构的影响

Initial impacts of two thinning methods on the spatial structure of Pinus massoniana plantations

【目的】探讨不同采伐方式和采伐强度对马尾松(Pinus massoniana)人工林空间结构的影响,为马尾松人工林林分结构优化和质量提升提供科学依据。【方法】以四川大茅坪国有林场马尾松人工林为研究对象,设置两种采伐方式:目标树经营(目标树数量0、100、167、233、300株/hm^(2))和基于目标树采伐蓄积强度设置相对应的传统抚育间伐(折算为0%、8.6%、16.1%、24.0%、29.2%),将目标树经营和传统抚育间伐中采伐强度为0株/hm^(2)合并记为CK。采用基于Voronoi图的林分结构参数(混交度、角尺度、大小比数、开敞度和竞争指数)和空间结构评价指数对林分空间结构进行评价。【结果】两种采伐方式对林分混交度的影响有差别,具体为:目标树经营下,林分混交度呈上升趋势,而传统抚育间伐无显著变化。两种采伐实施后,林分角尺度表现为显著增加的趋势,但林分仍处于均匀分布格局,目标树经营相较于传统抚育经营,林分随机分布比例提升相对较高,林分大小比数无显著变化。两种采伐方式均能提高林分开敞度,且随采伐强度增加呈现出上升趋势,在同一采伐强度下,开敞度值表现出目标树经营大于传统抚育间伐。林分竞争指数呈现显著下降的趋势,且在同一采伐强度下,竞争压力表现为目标树经营小于传统抚育间伐;两种采伐方式均显著提高了林分空间结构评价指数,增长率分别为28.8%-65.6%(目标树经营)和14.2%-44.5%(传统抚育间伐)。【结论】基于研究区内马尾松人工林现状,目标树经营较传统抚育经营下林分空间结构更趋于合理,马尾松近熟林合理的目标树保留木数量为233株/hm^(2)左右。

【Objective】This research aims to explore the effects of two tree thinning methods and intensities on the spatial structure of Pinus massoniana plantations,to provide a scientific basis for optimizing their structure and quality.【Method】Two thinning methods-crop tree management and traditional tending management-with five thinning intensities(0,100,167,233 and 300 trees/hm^(2))were established,at Damaoping State-Owned Forest Farm,an intensity of 0 trees/hm^(2) was used as a cotrol.Next we surveyed tree species(measuring tree height,diameter at breast height and distance between neighboring trees),drew Voronoi diagrams,and calculated spatial structure parameters for each stand:mingling index(M),neighborhood comparison(U),uniform angle index(W),opening degree(K),competition index(CI)and comprehensive evaluation index(Z).【Result】After thinning,the M parameters for crop tree and traditional tending management were heterogeneous:the former increased,while the latter did not significantly change.The W parameter increased,but the forest stands remained uniformly distributed.The forest was more randomly distributed with crop tree management than traditional tending management,while U parameters did not significantly change.Both thinning methods increased at the K parameter,which was larger for crop tree management than for traditional management.Both thinning methods saw a decrease in the CI parameter,likewise more so for traditional tending management.Finally,both crop tree and traditional management significantly improved the comprehensive evaluation indexes,which ranged from 28.8%to 65.6%and from 14.2%to 44.5%,respectively.【Conclusion】The crop tree management was more reasonable than that of the traditional tending,with the number of target trees approximately 233 trees/hm^(2) in the near-mature Masson pine forest.