落叶松人工林三维绿量测算

The estimation of the tridimensional green biomass of Larix gmelinii plantation

【目的】探究地基激光雷达获取单木因子的精度以及采用“体元模拟法”计算三维绿量的误差,探索基于TLS数据利用“体元模拟法”计算三维绿量可行性,构建三维绿量模型。【方法】以黑龙江省佳木斯市孟家岗林场42块样地的落叶松人工林为对象,样地面积为0.06~0.12 hm^(2),样木3366株。选取其中4块落叶松样地(样木208株),采用TLS扫描LiDAR360软件处理可得到单木因子参数,采用“体元模拟法”和Matlab编程实现4块样地(208株)内单木三维绿量计算,与“冠形公式法”计算的三维绿量进行精度分析;以地基提取树冠因子与通过Matlab计算的三维绿量构建单木三维绿量模型;单木三维绿量模型结合42块样地中的每木检尺数据计算每木三维绿量,通过样地中的每木三维绿量累加可得到样地三维绿量值,根据样地面积大小转化为对应的林分三维绿量,结合42块样地林分因子数据构建林分三维绿量模型。【结果】TLS获取的树冠因子数据满足精度要求,其中,胸径的提取效果最好P=97.14%,树高P=90.96%,冠幅P=89.25%,冠长P=77.92%;“体元模拟法”在步长k=0.1 m时在Matlab中计算三维绿量值最稳定;三因子单木三维绿量模型拟合与检验效果最好(R2=0.846,RMSE=0.250,MAE=0.210,MAPE=0.099,P=97.314%);双因子林分三维绿量模型拟合与检验效果最好(R2=0.706,RMSE=0.138,MAE=0.120,MAPE=0.013,P=99.142%)。【结论】TLS获取的树冠因子数据精度较高,采用“体元模拟法”计算三维绿量计算值较精确;通过TLS数据构建单木三维绿量模型和林分三维绿量模型可为探索大尺度区域三维绿量的估算提供新思路。

【Objective】This study aimed to investigate the accuracy of crown factor extraction from point cloud data by Terrestrial laser scanning(TLS),and the error of tridimensional green biomass calculated by the voxel simulation method,to verify the feasibility of using ground-based lidar data combined with the voxel simulation method to calculate tridimensional green biomass,and construct Larix gmelinii tridimensional green biomass models.【Methods】In this paper,42 Larix gmelinii in the sample plots in Mengjiagang in Jiamusi City,Heilongjiang Province were studied,and the sample plot area was 0.06-0.12 hm^(2),with 3366 trees.Four Larix gmelinii sample plots(208 trees)were selected,and the single tree factor parameters could be obtained by TLS scanning and LiDAR360 software processing.The“Voxel-based simulation method”was used to realize the calculation of the tridimensional green biomass of individual trees in the four Larix gmelinii sample plots(208 trees)by Matlab programming,and then the precision of tridimensional green biomass calculated by the“voxel simulation method”and“crown formula method”was analyzed.The tridimensional green biomass model of individual Larix gmelinii was constructed based on the crown factors extracted from the TLS and the tridimensional green biomass calculated by Matlab.The tridimensional green biomass model of single wood was combined with the data of each wood survey in 42 sample plots to calculate the tridimensional green biomass of each wood.The tridimensional green biomass of each wood in the sample plots could be accumulated to obtain the tridimensional green biomass of the sample plots,which was converted into the corresponding tridimensional green biomass of the stand according to the area of the sample plots.The tridimensional green biomass model of stands was constructed by combining stand factor data of the 42 plots.【Result】The crown factors obtained by TLS met the accuracy requirements,among which the extraction accuracy of diameter at breast height was the best(P=97.14%),followed by tree height(P=90.96%),crown width(P=89.25%)and crown length(P=77.92%).The“voxel simulation method”was the most stable to calculate the tridimensional green biomass value using Matlab with the step size k=0.1 m.The fitting and testing effect of the three-factor tridimensional green biomass model of individual trees was the best(R2=0.846,RMSE=0.250,MAE=0.210,MAPE=0.099,P=97.314%).The result of the two-factor tridimensional green biomass model of stands was the best(R2=0.706,RMSE=0.138,MAE=0.120,MAPE=0.013,P=99.142%).【Conclusion】The accuracy of crown factors obtained by TLS has high accuracy,and the“voxel simulation method”is more accurate to calculate the three-dimensional green value.The individual-tree model and stand model constructed by TLS data improve the accuracy of tridimensional green biomass estimation in large-scale areas,providing a new method for the tridimensional green biomass estimation in large-scale areas.