Research On The Method Of Estimating Above-ground Biomass Of Tamarix Shrubs Based On UAV Remote Sensing

Lop Nor is a typical representative of the extreme arid zone in China,where Tamarix plays an important ecological role in the sparsely vegetated Lop Nor.However,due to the sparsely populated area and harsh climatic conditions,no research has been conducted on the biomass of Tamarix shrubs.In this paper,we use UAV remote sensing results to extract relevant parameters based on field measurement data,and construct an above-ground biomass estimation model by object-oriented classification and canopy height model.The research is completed from the UAV remote sensing results to the estimation method of above-ground biomass,and a set of effective above-ground biomass estimation methods based on UAV remote sensing is constructed for Lop Nor Tamarix shrubs There are the following relevant conclusions in the research process.（1）Object-oriented area extractionThe results of this part extraction are:the overall classification accuracy is 91%,and the kappa coefficient is 0.82.The total number of Tamarix extracted from the images was 421,with a total vegetation coverage of 10114.96 m²,accounting for 6.32%of the total area of the study area covered by the images,and the average area was 24.03 m².The extraction results are consistent with the overall environmental characteristics of the study area,which is arid and with little vegetation distribution.Sandy land is the absolute main land type,accounting for93.68%of the total study area.（2）Height extraction based on UAV remote sensingThe height values extracted based on the canopy height model method were tested by paired t-test,0.01<p=0.028<0.05,with no difference at the significanceα=0.01 level,while differences were considered to exist at the significanceα=0.05 level.To achieve higher accuracy,a set of corrected values with correction factors was proposed using linear regression to remove systematic errors.The height values extracted by the modified canopy height model method passed the paired t-test with the measured data at the significance levelα=0.05 level,p=0.998>0.05,and improved the overall accuracy from 82.73%to 88.47%,which has some extension value.The height values extracted based on human-computer interaction interpretation passed the paired t-test at the significance levelα=0.05 level,p=0.244>0.05,and the overall accuracy of this method reached 94.93%,and the height extraction accuracy was higher than that of the modified canopy height model method.The disadvantages are that it is manually operated,time-consuming and the accuracy is related to the interpretation level of the interpreters,which makes it difficult to be used on a large scale.（3）Construction of above-ground biomass estimation model for TamarixThe above-ground biomass estimation model of Tamarix based on the canopy area S is:=0.691^1.221（R²=0.851,F=143.026）,and the average estimation accuracy is 79.9%.F-test for actual and estimated values,p=0.3218>0.05,no significant difference between actual and estimated values at the significance levelα=0.05.The model requires only one factor of canopy area and is suitable for above-ground biomass estimation of Tamarix in cases where only area is available.The above-ground biomass estimation model for Tamarix based on the derived factor SH was:=0.86（）^1.051（R²=0.892,F=205.699）,with an average estimation accuracy of82.26%,which is 2.36%better than the single canopy area estimation method.An F-test was performed on the actual and estimated values,p=0.2616>0.05,and there was no significant difference between the actual and estimated values at the significance levelα=0.05.The model requires the participation of two factors,scrub height and canopy area,and is suitable for estimating above-ground biomass of Tamarix when both height and area can be obtained.In this paper,the total above-ground biomass was estimated as 9925.10 kg and the biomass per unit area was 0.98 kg/m² based on the modified canopy height model method,and the total above-ground biomass was estimated as 10417.68 kg and the biomass per unit area was 1.03kg/m² by the human-machine interactive interpretation method,which can be used as a reference for rapid estimation of above-ground biomass of Tamarix.