湖南次生栎林空间结构优化

Spatial structure optimization of Quercus in Hunan

以湖南省国家森林连续清查中栎类为优势树种的样地作为研究对象,通过空间结构指数结合生长量选取合适的间伐木,为湖南栎类次生林的结构调整提供优化方法。运用邻域分析方法对每一个样地创建Voronoi图,分析林分空间结构特征。根据全混交度、角尺度、大小比数、竞争指数4个主要空间结构指数并运用乘除法的思想构建综合空间结构模型。根据每一株林木的综合空间结构指数选取合适的间伐木进行优化。用相容性林分生长收获模型模拟最优断面积,用最优的断面积控制间伐量,使得林分被间伐后,其生长活力能得到提高,在样地结构优化的同时达到提质增量的目的。以2 277号样地为例,根据模型确定样地间伐木为21株,株数间伐强度为16.27%,且间伐后的林分树种个数与径阶个数都未减少;间伐后的林分全混交度提高3.70%,林分整体竞争强度降低31.74%,林分的角尺度降低0.46%,林木的分布格局趋于随机分布,林分空间结构指数增加160.12%,使得林分的空间结构得到大幅的改善。林分的结构越合理,稳定性就越高,发挥的功能作用就越多。本研究以湖南栎类次生林为研究对象,在提出林分空间结构优化目标的基础上,结合了生长量的优化,构建林分间伐空间结构优化模型和每个年龄段的最优断面积预测曲线,为栎类次生林空间结构优化调控和林分提质增量措施的制定奠定理论基础。

Taking the sample plots of Quercus species as dominant species in Hunan national forest continuous inventory as the research object, optimally cutting trees were selected through spatial structure index combined with growth, which provided an optimization method for structural adjustment of secondary forests of Quercus species in Hunan province.The Voronoi map was created for each sample plot by using the neighborhood analysis method, and the spatial structure characteristics of the stand were analyzed. According to the four main spatial structure indices of complete mingling, uniform angle index, neighborhood comparison and competition index,a comprehensive spatial structure model is constructed by using the idea of multiplication and division. According to the comprehensive spatial structure index of each tree, suitable thinning trees were selected for optimization. Simulating the Optimum Section Area with Compatible Stand Growth and Harvest Model, and the optimal cross-sectional area is used to control the thinning amount, so that the growth vigor of the stand can be improved after thinning, and the purpose of improving quality and increment can be achieved at the same time of optimizing the sample plot structure.Take 2277 sample plot as an example,According to the model, 21 trees were thinned in the sample plot, the thinning intensity was 16.27%, and the number of tree species and diameter rank did not decrease after thinning;the complete mingling degree of thinning increased by 3.70%, the overall competition intensity of stand decreased by 31.74%, the uniform angle index of stand decreased by 0.46%, the distribution pattern of trees tended to random distribution, and the spatial structure index of stand increased by 160.12%, which made the stand more competitive. The spatial structure has been greatly improved.The more reasonable the stand structure, the higher the stability and the more function it plays. Based on the objective of optimization of spatial structure of oak secondary forests in Hunan province and the optimization of growth, the optimal model of spatial structure of thinning and the prediction curve of optimal sectional area for each age group were constructed, which laid a theoretical foundation for the optimal regulation of spatial structure of oak secondary forests and the formulation of incremental measures for improving forest quality.