Tridimensional Green Biomass Converting Leaf Area In Forest Branches Based On The Light Detection And Ranging

Leaf area is an important parameter to evaluate the ecological benefit of forest,which significantly affects photosynthetic efficiency and efficiency for solar energy utilization,while tridimensional green biomass(TGB)better reflects the spatial structure characteristics.The quantification conversion relation of leaf area and TGB has important theoretical and practical significance.Taking Larix olgensis plantation and Quercus mongolica secondary forest at Qingyuan Experimental Station of Forest Ecology Chinese Academy of Sciences(CAS)for the research object,a new plant leaf area measurement method is proposed in this paper by using Digimizer digital image method based on the actual measurement of leaf area,of which a three-dimensional model is established by using LiDAR technique based on the unit of the primary branch.Secondly,a TGB measurement process and method is discussed by utilizing LiDAR and a quick estimation method of TGB based on point cloud data is proposed.The method is preliminarily proved to measure coniferous species and broad-leaf species simultaneously and is extremely practical.In addition,the quantitative conversion relation between TGB and leaf area is constructed by utilizing the stepwise regression method,which provides conversion parameter for forest leaf area inversion of TGB in large area.The main conclusions are as below:1.The filling method,a quick estimation method of filling type TGB based on the point cloud distribution is proposed in the paper.When the laser transmitting frequency is 300,000 points/second and the point cloud dilution is 70%,the point cloud is replaced by 6.075cm3 geometry by taking branch point cloud space distribution as the framework.The computation formula is TGB=6.075N,of which N is the number of point cloud.As tested in precision,the measuring precisions of L.olgensis and Q.mongolica at the levels of ?=0.05 and ?=0.01 are(92.416%,89.958%)and(92.066%,88.512%)respectively.The method doesn't need to distinguish the species and judge the tree form,but estimates TGB quickly.2.After comparison analysis the different measuring methods of TGB on a basis of acquiring point cloud data by using LiDAR technique,it is found that the measuring values by using filling method,3DMAX topology and TIN network are smaller than that using traditional method obviously and the result approximates to the fact more.The filling method and 3DMAX topology are more suitable for TGB determination than TIN network and traditional method.3.After comparing the measuring result of leaf area by using common method and Digimizer digital image method,Digimizer digital image method is proved to be suitable for the leaf area determination of both Q.mongolica and L.olgensis.The determination result is accurate,stable and reliable.The method is operated simply and processed by batch without being affected by resolution,image storage format and scanning mode.4.The branch leaf area of L.olgensis and Q.mongolica is significantly correlated to the branch characteristic.The correlation between L.olgensis branch leaf area and branch characteristics in sequence is TGB(0.856)>d2(0.812)>d2L(0.795)>d(0.769)>L(0.654);the correlation between Q.mongolica branch leaf area and branch characteristics in sequence is TGB(0.887)>d(0.707)>d2(0.671)>d2L(0.629)>L(0.487).5.The quantitative conversion relation between branch TGB and leaf area is established in the paper.For L.olgensis,BLA=3.726TGB+0.223,it's coefficient of determination(R2)was 0.733;for Q.mongolica,BLA=3.974TGB+0.963,it's coefficient of determination(R2)was 0.788.When a=0.05 and a=0.01,the precisions of them are(92.457%,88.540%)and(92.414%,89.690%)respectively.Thus,TGB can be considered as the optimal explanatory variable of branch leaf area.