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Scientia Silvae Sinicae ›› 2025, Vol. 61 ›› Issue (8): 129-141.doi: 10.11707/j.1001-7488.LYKX20240390

• Research papers • Previous Articles     Next Articles

Inversion Model of Aboveground Biomass at Individual Tree Scale Based on the Multiple Features of UAV Remote Sensing

Yujiao Zhang1,Hengqian Zhao1,2,*(),Hancong Fu1,Ge Liu1,Xiadan Huangfu1,Xuanqi Liu1   

  1. 1. College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing) Beijing 100083
    2. Inner Mongolia Research Institute, China University of Minning and Technology (Beijing) Erdos 017010
  • Received:2024-06-24 Online:2025-08-25 Published:2025-09-02
  • Contact: Hengqian Zhao E-mail:zhaohq@cumtb.edu.cn

Abstract:

Objective: The aim of this study is to estimate aboveground biomass (AGB) at individual tree scale in northern forests by synergistically utilizing UAV-LiDAR and UAV-RGB data. Pinus sylvestris var. mongolica and Populus. in Zhangwu County were used as the research object to investigate the influence of using combined data versus single data on AGB estimation in coniferous and broadleaf forests. The findings are to provide technical references for precise prediction of AGB at individual tree scale in windbreak and sand fixation plantations in Zhangwu County. Method: Multiple features at individual tree scale, including height, intensity, density, crown structure, spectrum, texture and vegetation index, were extracted from LiDAR point clouds and digital orthophoto map (DOM) derived from RGB optical imagery. Permutation importance (PI) and Boruta methods were used to select feature subsets. Combining these features with the aboveground biomass (AGB) data of individual trees calculated from field-measured tree height and diameter at breast height, three typical machine learning methods, including random forest (RF), extreme gradient boosting (XGBoost), and categorical features gradient boosting (CatBoost), were adopted to construct biomass estimation models for the two tree species, P. sylvestris var. mongolica and Populus. The modeling results using only LiDAR data, only DOM data, and a combination of both methods were compared. Result: 1) Point cloud height and crown structure were identified as key features for AGB estimation at individual tree scale for both species, whereas texture features only positively influenced the estimation of AGB for P. sylvestris var. mongolica. 2) For P. sylvestris var. mongolica, the estimation accuracy of AGB at individual tree scale based on combined data was highest, outperforming models based on single LiDAR and RGB imagery. The optimal models for the three datasets were ALL-PI-XGBoost, LiDAR-PI-XGBoost, and DOM-PI-RF, with R2 of 0.77, 0.69, and 0.67, and RMSE of 10.94, 12.75, and 13.16 kg·plant?1, respectively. For Populus, the estimation accuracy of AGB at individual tree scale was comparable when using combined and single LiDAR data, and both outperformed the model based on single RGB imagery. The optimal models for the three datasets were ALL-PI-XGBoost, LiDAR-Boruta-XGBoost, and DOM-Boruta-CatBoost, with R2 of 0.85, 0.85, and 0.59, and RMSE of 17.63, 17.11, and 28.99 kg·plant?1, respectively. Conclusion: The high-density point clouds and high-resolution images obtained from two types of low-cost UAV remote sensing technology can achieve high-precision, fast, and non-destructive estimation of individual tree aboveground biomass in the windbreak and sand fixation plantations in Zhangwu County. The use of combined data versus single data has different impacts on AGB estimation at individual tree scale in coniferous and broadleaf forests, with combined data significantly improving the accuracy of AGB estimation for P. sylvestris var. mongolica.

Key words: UAV-LiDAR, UAV optical imagery, individual tree scale, aboveground biomass (AGB), machine learning

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