Application Of Uav In Inversion Of Aboveground Biomass And Carbon Storage Of Dense Low Shrub Mangrove

The investigation of mangrove biomass and carbon storage is the key to evaluate the carbon sink potential of mangrove ecosystem.Because of its convenience,wide coverage and high spatial resolution,UAV has been applied in the large-scale stand biomass in mangroves dominated by tree species(Sonneratia caseolaris)and sparsely distributed through single tree segmentation technology,and has good accuracy.However,for dense low shrub mangroves with Limited crown height difference,it is unable to achieve high-precision single tree identification,so it is difficult to estimate their aboveground biomass and carbon storage.In order to solve this problem,this study takes Xiao Guan Sha in Beihai City,Guangxi Zhuang Autonomous Region as the research area,and takes the dense low shrub dominant tree species(Avicennia mariana and Kandelic candel)in the study area as the study object.Based on UAV aerial survey,the Canopy Height Model is obtained through pretreatment operations such as aerial belt splicing,image synthesis,The diagram of Aerial triangulation analysis,point cloud classification and revision(revision to solve the problem of mixing low mangrove and beach background),spatial interpolation and so on;On this basis,on the one hand,364 single tree samples of Avicennia mariana and103 single tree samples of Kandelic candel in the study area were randomly selected,and the ecological characteristic indexes such as tree height,crown diameter and base diameter of single tree samples were measured,which were substituted into the specific allometric growth equation to obtain the aboveground biomass of single tree samples.The single tree samples that are close to some single trees and can be recognized by naked eyes but difficult to be recognized by UAV were combined to form the crown patch of combined wood samples,The aboveground biomass of 81 single tree Avicennia mariana sample crown patches,63 single tree and Kandelic candel sample crown patches,24combined wood and Avicennia mariana sample crown patches and 10combined wood Kandelic candel sample crown patches were obtained;On the other hand,according to the Canopy Height Model extracted by UAV,the canopy projection area and surface volume corresponding to the canopy patches of single wood samples and combined wood samples are obtained,which can be used as the inversion factor of aboveground biomass of mangrove;80%of the samples are used for modeling and20%for validation.Innovatively use single factor(only canopy projection area or surface volume)and multi factor(comprehensive use of canopy projection area and surface volume)to carry out fitting regression and accuracy evaluation,and finally build a UAV inversion model suitable for the aboveground biomass of dense low shrub mangrove vegetation.Finally,the carbon conversion coefficients(carbon content per unit aboveground biomass of mangrove)of the two mangrove vegetation were measured,and the carbon stock of aboveground biomass of Mangrove in the study area were further estimated.The results show that:(1)On the basis of UAV image preprocessing,the mangrove canopy height model obtained by Kriging interpolation and TIN interpolation has the highest accuracy.The goodness of fit R~2 between the single tree height(extracted tree height)obtained by this method and the single tree height(measured tree height)measured in the field is 0.95,and the average relative error is 5.6%,which meets the requirements of forestry investigation.(2)The precision of the multi factor biomass inversion model is the highest in the two mangroves of Avicennia mariana and Kandelic candel.Among them,the optimal biomass inversion model of Avicennia mariana is a binary first-order function model,and the model R~2 is 0.97.The overall average relative errors of modeling and verification results are16.47%and 18.50%respectively;The optimal biomass inversion model of Kandelic candel is a binary power function model,and its model R~2 is0.92.The overall average relative errors of modeling and verification results are 13.68%and 16.28%respectively.(3)Based on the modeling results of this study,the total aboveground biomass of Avicennia mariana and Kandelic candel in the study area are about 1686.90 t and 81.27 t respectively;The carbon conversion coefficients of the two mangrove vegetation are 0.4303 and0.4548 respectively.When the biomass and carbon conversion coefficient are multiplied,the total aboveground carbon stoge of Avicennia mariana and Kandelic candel in the study area are about 725.87 t and 36.96 t respectively.