为了提高传统样地法森林资源调查的效率,本实验设计研究一种基于七株木法的森林资源扰动监测方法。在Voronoi图与Delaunay三角网基础上,运用高精度的免棱镜全站仪获取样地林木特征参数等数据,结合南方测绘CASS软件,提出建立空间结构单元的最优方法;在北京百花山选取有代表性实验样地5块,通过森林资源调查来分析基于七株木法的森林资源扰动监测方法的优劣性。结果表明:每个七株木法样地的面积在0.005~0.015hm2之间;七株木法解决了因传统测高仪器精度低不能获取树高生长量的难题;单独七株木在混交林、天然林获取林木特征参数中的精度稳定性低于人工林和单层林,但样地数量增加能大幅度提高其精度;通过以标准样地法林分特征数据作为真值检验七株木法,数据表明,林分平均高中误差为±0.005mm,树高生长量相对误差为1%,林分密度抽样精度区间为83%~98%,林分蓄积量抽样精度在92%以上。七株木法具有高效、精准、数字化等优点,利用该方法对林地持续观测,通过数据对比分析可以对森林资源扰动进行监测。
In order to improve the efficiency of the investigation of forest resources,a design for monitoring forest resources disturbance based on 7-tree is developed,which proceeds from the Voronoi diagram and Delaunay triangulation by constructing spatial structure units that is achieved by some characteristic parameters on sample tress acquired by high-precision prism total station with the aid of south CASS software.In this study,on analysis of forest resource inventory data sampled from five representative plots in Baihua Mountain of Beijing,the proposed technique is compared with other traditional methods.The optimal plot covers between 0.005 and 0.015 ha,which can resolve the problem that the tree height growth could not be measured due to the low precision in conventional altimeters.The results show that there has less steadiness in precision of the data collected in mingled forests and wildwoods than those from plantation and single-layered forest.Fortunately,the precision can be improved with the more plots.From these data,it can be indicated that in the mean stand height,the error is ±0.005mm and in the tree height growth,the relative error is 1%,and the Sampling accuracy can remain 83%~98% in the stand density and over 92% in the stand stock.This method is advantageous in many aspects over those available,such as efficiency,precision and digitization,which is essentially easy to operate in monitoring forest resources disturbance.
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