基于第一着枝角度的罗田垂枝杉树冠表面积预估模型研究

Estimation of crown surface area of Cunninghamia lanceolata var.luotian based on the first branch angle

以湖北省咸宁市贺胜桥镇罗田垂枝杉试验林为研究对象,随机设置30块标准样地,共调查71株标准木的解析数据;分别使用传统几何体法、基于第一着枝角度的几何体法以及分层切割法计算罗田垂枝杉树冠表面积,并将3种方法得到的数据进行对比;将71株标准木的解析数据分为建模组数据与模型检验组数据,选用异速生长方程为拟合方程,构建垂枝杉树冠表面积预估模型并检验。结果表明:使用3种方法计算得到的树冠表面积的大小为分层切割法的>基于第一着枝角度的几何体法的>传统几何体法的;以分层切割法作为参照,相比于传统几何体法,基于第一着枝角度的几何体法计算得到的树冠表面积更加准确。罗田垂枝杉的树冠表面积与胸径、冠长、冠幅均呈显著正相关。增加变量可提高模型的拟合精度;以胸径、冠长、冠幅为变量的模型CSA=1.97D^(0.07)CW^(0.94)CL^(0.87)为最优模型,其拟合精度高达96.89%,说明该模型能较好地预估罗田垂枝杉的树冠表面积。

Taking the Cunninghamia lanceolata var.luotian experimental forest in Heshengqiao Town,Xianning City,Hubei Province as the research object,a total of 30 standard plots were set up to investigate the analytical data of 71 standard trees;the traditional geometric method,the geometric method based on the first branch angle and the geometric method based on the first branch angle were used in this study,respectively.The layered cutting method was used to calculate the crown surface area of C.lanceolata var.luotian,and the data obtained by the three methods were compared;the analytical data of 71 standard trees were divided into modeling group data and model testing group data,and the allometric growth equation was used to fit the equation.Therefore,a model for estimating the crown surface area of weeping fir was constructed and tested.The results show that the crown surface area calculated by the three methods was shown as the following order:layered cutting method>geometry method based on the first branch angle>traditional geometry method.Taking the layered cutting method as a reference,compared with the traditional geometry method,based on the crown surface area calculated by the geometric method of the first branch angle is more accurate;there was a significant positive correlation among the crown surface area of the C.lanceolata var.luotian and the diameter at breast height,crown length and crown width.Adding variables can improve the fitting accuracy of the model.Based on the diameter at breast height,crown width,The model with crown length and crown width as variables CSA=1.97D^(0.07)CW^(0.94)CL^(0.87)was the optimal model,and its fitting accuracy was as high as 96.89%,indicating that this model could better predict the Cunninghamia lanceolata var.Luotian canopy surface area.