利用手持式超站测树仪测量林分空间结构参数

    Forest stand spatial structure measurement method using handheld tree measurement smart station

    • 摘要: 针对传统测量方法准确度不高和外业投入大,该文提出了一种基于手持式超站测树仪测量空间结构参数的原理与技术方法。其原理是通过测量参照树和4株邻近木的坐标,解算夹角并计算角尺度;混交度和大小比值测量数据由仪器自动记录并计算、显示结果。在北京市奥林匹克森林公园内选择1块样地开展试验,结果表明:角尺度测量与传统直接判读法相比,测量结果相对误差在2%以内。混交度测量结果与传统方法完全一致,测量效率是直接判读法的3倍左右;大小比数测量结果均值与直接判读法测量均值相对误差小于4%。该文方法测量林分空间结构参数具有角尺度、大小比数和混交度值可以由单人测量、现场获得,由仪器电子化存储的特点,克服了传统角尺度测量中无法测量参照树和临近木胸高树心坐标导致角尺度计算错误问题;且在测量角尺度时参照树和临近木分布图可以根据测量数据由内业绘制、直观显示。该研究为林分空间结构参数测量提供参考。

       

      Abstract: Abstract: Spatial structure is an important characteristic of forest and spatial distribution pattern is one part of researches on population spatial behavior.Based on the relationship of neighborhood trees, three kinds of stand spatial structure parameters including uniform angle index,mingling and dominance was proposed by Professor Gangying Hui. In the past decade, stand spatial structure parameters are widely used to analyze stand spatial structure, calculate trees dominance, judge competition among trees, measure species diversity and recover or reconstruct stand structure at domestic and international study.. Measurement accuracy of spatial structural parameters (uniform angle index, mingling degree, and dominance) has a significant role in studying stand spatial structure. In the traditional direct interpretation method(DIM), it is difficult to measure the angle between reference tree and 4 nearest neighbor trees. For this method, the error derived from tree diameters at breast height is not considered in the process of measurement, so uniform angle index value is inaccurate. Moreover, based on DIM, other two parameters of mingle degree and dominance measurement required at least two operators, one person completed measurement and the other recorded field data, thus it is impossible to calculate the observing results immediately In this paper, a new measuring method named as HSSM was proposed using handheld smart station to measure stand spatial structure parameters in order to enhance measurement precision and accuracy, decrease field investigation workload. For measuring uniform angle index , the angle between reference tree and four nearest neighbor trees is not measured directly. Firstly, X-Y coordinates of reference tree and four nearest neighbor trees are measured using handheld smart station. Secondly, the diameters at breast height of five trees are measured corresponding with each tree, specifically, diameters at breast height measurement is to obtain center coordinates of five selected trees so as to increase angle calculation accuracy. Finally, reference tree as central point, intersection angles between four nearest neighbor trees are resolved according to the law of cosines. According to the above-mentioned measurement method, experiment was carried out in one stand forest plot (100 m×100 m) which located at Beijing Olympic Forest Park by three operators. The relative error of uniform angle index average value of HSSM was 2% less than that of DIM, average time-consuming (single person) of HSSM was 90.1s more than that of DIM (double person, 40.7 s), and measurement efficiency of HSSM was 8% lower than that of DIM. The mingle measurement result of HSSM were as the same as that of DIM, but the average time-consuming (single person) of HSSM was 21.5s less than that of DIM (double person, 32.2 s), measurement efficiency of HSSM was about 3 times that of DIM. The results of dominance relative error was 4% between HSSM and DIM, but the average time-consuming (single person) of HSSM was 74.8s more than that of DIM (31.05 s for double person), measurement efficiency of HSSM was 20% lower that of DIM. HSSM had the advantages of single person operation, display and storage directly by the equipment. Moreover, compared with the DIM, HSSM resolved the problem that DIM could not measure the tree center coordinate at breast height of reference tree and nearest neighbor tree , and for HSSM, the distribution of reference tree and nearest neighbor tree could draw conveniently and visually display according to measuring data in the process of interior work . This research can provide references for measuring forest spatial structure measurement accurately and efficiently.

       

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