| 摘要: |
| 【目的】探讨择伐强度对云冷杉天然次生林空间结构的影响，为天然林空间结构优化提供依据。【方法】在吉林省汪清县金沟岭林场，选择不同择伐强度（0%，20%，30%，40%）的典型云冷杉天然次生林各设置3块样地，根据样地中林木坐标点图构建林分的Voronoi图，同时建立TIN三角网，结合Voronoi图结点距离判定对样地进行边缘校正，利用角尺度、混交度、竞争指数、林木点密度、林层指数和开阔比数6个空间结构参数，对比分析不同择伐强度下云冷杉天然次生林林分及林分中云杉、冷杉、红松、紫椴、枫桦等5个主要树种的空间结构变化。【结果】择伐对云冷杉林分空间分布格局影响不大，择伐后10年各林分处于均匀分布状态，5个主要树种亦呈均匀分布。不同择伐强度云冷杉林分的平均混交度为0.630~0.716，林分处于强度混交状态，其中40%择伐强度下林分的混交度最高，20%择伐强度次之，5个主要树种均属强度或极强度混交。采用竞争指数和林木点密度分析不同择伐强度下云冷杉林分的林木竞争压力，得到相似的排序结果，均为0%>30%>40%>20%，可知择伐强度20%林分的竞争指数和林木点密度皆小于其他样地，林分所受竞争压力最小，有较大的生长活力，其中冷杉作为优势种所受竞争压力较大。各林分中林木大部分位于中上层，林分整体垂直分层较单一，择伐强度30%林分的林层指数为0.398，林层丰富度高于其他林分，冷杉、红松、云杉多占据林分上层。不同择伐强度云冷杉林的平均开阔比数为0.712~0.743，林分整体处于开阔状态，其中择伐强度20%林分的开阔比数高于其他林分，说明择伐强度20%林分内光照条件和透光性优于其他林分；各林分中红松、冷杉、云杉开阔比数均较高，紫椴、枫桦开阔比数均较低。【结论】择伐强度20%云冷杉林分的状态整体优于其他林分，择伐强度30%林分的垂直层次丰富度较高，因此云冷杉天然次生林采伐强度在20%~30%较合理；另外需结合实际情况对林分进行补植，补植选择中心木附近且将角尺度调整为0.5左右，建议补植云杉、红松。 |
| 关键词: 择伐强度 云冷杉天然林 林分空间结构 Voronoi图 |
| DOI： |
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| 基金项目:国家重点研发计划项目“云冷杉针叶林抚育更新技术”（2017YFC050410101） |
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| Structure of spruce-fir forest under different selected cutting intensities based on Voronoi diagram |
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YU Yitong,WANG Xinjie,LIU Li,et al
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| Abstract: |
| 【Objective】The impacts of selective cutting intensity on spatial structure of natural secondary forests of spruce-fir were discussed to provide basis for spatial structure optimization of natural forests.【Method】In Jingouling forest farm of Wangqing County,plots of the typical spruce-fir natural secondary forests with 4 different selective cutting intensities of 0%,20%,30%,and 40% were selected.Spatial structure changes were calculated with spatial structure parameters including uniform angle index,mingling,competition index,point density,layer indices and open radio using the method of Voronoi diagram and the TIN triangulation according to the coordinate point map of forest in sample plots and combined with a novel edge correction method called distance determinant of Voronoi nodal.The changes of five main tree species (Picea jezoensis Carr.,Abies nephoriepis (Trantv.) Maxin,Pinus koraiensis Sieb.et Zucc.,Tilia amurensis Rupr.,and Betula costata Trautv.) (3 plots each) were compared and analyzed.【Result】Selective cutting had less effect on spatial distribution of forest stands.Ten years after selective cutting,the stands were distributed uniformly,and the five main tree species were also uniformly distributed.The average mingling of sample plots with different selective cutting intensities was 0.630-0.716,and the stands were in mixed state of strength.The mingling of stand was the highest under 40% selective cutting intensity,followed by 20%,and the mixed states of five main tree species were intensive or extremely intensive.Forest competition pressure was analyzed by using competition index and forest point density index and similar competition sequences were 0%>30%>40%>20%.The competition index and point density of 20% selective cutting plots were lower than other plots,and the stands suffered the least from competitive pressure and had greatest growth vitality.A.nephoriepis was more competitive as a dominant species.Most trees were located in the upper middle layer,the overall vertical layering of forest stands was relatively simple,and the layer index of the 30% selective cutting plots was 0.398,indicating the space utilization rate was higher than other plots.P.jezoensis,A. nephoriepis and P.koraiensis mostly occupied the upper layer.The average open ratio of sample plots with different selective cutting intensities was 0.712-0.743,and the stands were in an open state.The open ratio of the 20% selective cutting plots was higher than that of other plots, indicating that the lighting conditions and light transmission in the 20% selective cutting plots were better than those in other plots.The open ratios of P. jezoensis,A. nephoriepis and P. koraiensis were higher,and the open ratios of T.amurensis Rupr.and B. costata Trautv.were lower.【Conclusion】The stand state of 20% selective cutting intensity sample plots was better than others, and the vertical layer richness of 30% selective cutting intensity sample plots was higher.It is suggested that the reasonable cutting intensity of natural secondary forests of spruce-fir is 20%-30%.P. jezoensis and P. koraiensis should be replanted near the center wood and the uniform angle index should be around 0.5. |
| Key words: selective cutting intensity natural mixed spruce fir forest stand spatial structure Voronoi diagram |
