基于空间结构优化的长白落叶松人工林分间伐模型构建

Establishment of thinning models for Larix olgensis plantation based on spatial structure optimization

【目的】构建一整套林分空间结构优化的评价方法,以此为基础建立林分间伐模型,以期为森林抚育经营提供科学的间伐方案。【方法】以长白落叶松人工林为研究对象,将林木调查因子树高、胸径、冠幅标准化计算后,加权到Delaunays三角网中并确定林分空间竞争单元,计算样地角尺度、大小比数、密集度、开敞度、竞争指数、混交度这6个林分空间结构参数并使用熵权法赋予各参数权重,结合乘除法思想对其进行多目标规划,进而计算出林分空间评价指数(SEE)与林分空间评价等级(SET)。以SEE为基础构建林分均分间伐模型(该模型可以选定林分中空间结构较差的林木并让其较为均匀地分布在林分中)并将其应用到实际样地中。在露水河林业局东升林场设立了20块面积为0.06 hm^(2)的落叶松人天混林分的正方形样地,利用样地数据分析间伐前后6个林分空间结构参数、SEE、SET、林冠投影图的变化以验证模型的合理性。【结果】将SEE应用到调查林分中发现,20块样地SEE均值为0.138~0.216,SET分布在1级和2级,其中85%的样地属于1级,15%的样地属于2级,根据SET的定义可以判定该林分质量较差,需要进行优化。以评级指数最低的z17号样地为例,对均分间伐模型进行应用后发现,各林分空间结构参数均往优的方向发展,且样地SET从1级提升到2级。【结论】以加权Delaunays三角网为基础,结合乘除法与熵权法思想所构建的林分均分间伐模型,改善了同类模型所存在的缺陷,可以显著优化林分空间结构,对于林分生长与收获预估模型构建具有重要的参考意义。

【Objective】Taking Larix olgensis plantation as the research object,a set of evaluation methods of stand spatial structure optimization was constructed,and based on this,a stand thinning model was constructed to provide a scientific thinning scheme for forest tending management.【Method】After standardized calculation,the forest survey factors such as height,DBH and crown width were weighted to Delaunay triangulation network and the stand spatial competition unit was determined.The six forest spatial structure parameters of sample plot uniform angle index,dominance,crowding,stand open degree,competition index and mingling degree were calculated,and the entropy weight method was used to give the weight of each parameter.Combined with the idea of multiplication and division,the multi-objective programming was carried out,and then the stand spatial evaluation index(SEE)and stand spatial evaluation level(SET)were calculated.Based on SEE,a stand average thinning model was constructed(This model could select the trees with poor spatial structure in the stand and make them more evenly distributed in the stand)and applied to the actual plot.In Dongsheng Forest Farm of Lushuihe Forestry Bureau,20 square plots of Larix mixed forest with an area of 0.06 hm^(2) were established.The changes of spatial structure parameters,SEE,SET and the canopy projection map of 6 stands before and after thinning were analyzed to verify the rationality of the model.【Result】SEE was applied to the survey stand,and it was found that the mean SEE of the 20 plots was between 0.138 and 0.216,and SET was distributed at level 1 and level 2.Among them,85%of the plots belonged to level 1,and 15%of the plots belonged to level 2.According to the definition of SET,the stand quality could be judged to be poor,which needed to be optimized.Taking the sample plot z17 with the lowest rating index as an example,after the application of the average thinning model,it was found that the spatial structure parameters of each stand developed in the direction of optimization,and the SET of the sample plot was upgraded from level 1 to level 2.【Conclusion】Based on the weighted Delaunay triangulation,the stand average thinning model constructed by combining the multiplication and division method and the entropy weight method can improve the defects of similar models,optimize the spatial structure of the stand,and has important reference significance for the construction of stand growth and harvest prediction model.