机载LiDAR数据估算样地和单木尺度森林地上生物量  

Forest above-ground biomass estimation at plot and tree levels using airborne Li DAR data

作　　者：李旺[1,2] 牛铮[1] 王成[3] 高帅[1] 冯琦[4] 陈瀚阅[5] 

机构地区：[1]中国科学院遥感与数字地球研究所遥感科学国家重点实验室,北京100101 [2]中国科学院大学,北京100049 [3]中国科学院遥感与数字地球研究所数字地球重点实验室,北京100094 [4]中国林业科学研究院资源信息研究所,北京100091 [5]福建农林大学资源与环境学院,福建福州350007

出　　处：《遥感学报》2015年第4期669-679,共11页NATIONAL REMOTE SENSING BULLETIN

基　　金：国家重点基础研究发展计划(973计划)(编号:2013CB733405;2010CB950603);国家自然科学基金(编号:41201345)

摘　　要：利用机载激光雷达点云数据,结合大量实测单木结构信息,分别从样地和单木尺度估算了森林地上生物量AGB。首先,利用局部最大值单木提取算法提取了每个样地内的单木结构参数,并针对样地和单木尺度分别计算了一组激光雷达变量。然后,利用激光雷达变量和地上生物量及其两者的对数形式,从样地和单木尺度分别构建了估算模型。最后,针对两种尺度估算过程中存在的不确定性进行了详细讨论。结果表明:(1)样地和单木尺度模型估算的森林地上生物量与地面实测值都具有明显的相关性,且对数模型估算效果要优于非对数模型;(2)样地尺度模型估算效果(R2=0.84,rRMSE=0.23)明显优于单木尺度模型(R2=0.61,rRMSE=0.46);(3)按树木类型分别进行估算可以提高单木地上生物量的估算精度;(4)不论是样地还是单木尺度地上生物量估算都存在一定的不确定性,与样地尺度相比,单木尺度估算过程的不确定性更大,这种不确定性主要来自单木识别过程。Forest Above-Ground Biomass（ AGB） is a critical indicator of carbon cycle in the ecosystem. In this study,we estimated AGB at tree and plot levels using airborne Li DAR point clouds,together with numerous field-measured structure information of tree. We compared methodologies and analyzed uncertainties in the estimation of AGB at different spatial levels,to provide supportive suggestions for the management and monitoring of forest resources. First,Li DAR metrics were calculated at plot and tree levels. Tree-level Li DAR metrics were calculated on the basis of the results from individual tree delineation using local maxima algorithm. Second,stepwise regression models were established between Li DAR metrics and AGB and their logarithm-transformed data. Apart from regression models established by combining different tree species,regression models were also developed for two dominant tree species in our study area. Finally,uncertainty analyses were conducted on AGB estimation at plot and tree levels.Li DAR points with different point densities were generated using thinning strategy to analyze the effects of point density variation on Canopy Height Model（ CHM）,the basic data source for individual tree delineation. The number of plots with specific point density was counted. Results were as follows.（ 1） Li DAR-estimated AGB was highly correlated with the field-estimated ones at plot and individual tree levels. The logarithm-transformed models obtained higher estimation accuracy than the non-logarithm-transformed models.（ 2） Regression model developed at the plot level（ R2= 0. 84,rRMSE = 0. 23） showed better performance than that at the tree level（ R2= 0. 61,rRMSE = 0. 46）.（ 3） Regression models built for the two dominant tree species improved the estimation accuracy of individual tree AGB; they obtained higher R2（ 0. 67 and 0. 69） and lower rRMSE（ 0. 29 and 0. 21） than the combined models.（ 4） AGB estimation at plot and tree levels suffered from uncertainty problems. Not all the

关 键 词：机载激光雷达 样地和单木尺度 森林地上生物量 不确定性分析 

分 类 号：S771.8[农业科学—森林工程] TN958.98[农业科学—林学]