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Scientia Silvae Sinicae ›› 2023, Vol. 59 ›› Issue (8): 12-21.doi: 10.11707/j.1001-7488.LYKX20210955

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Estimation on Canopy Closure for Plantation Forests Based on UAV-LiDAR

Xiaohui Yang1,Jinzhuo Wu2,Haoran Liu1,Hao Zhong1,Wenshu Lin1,*   

  1. 1. College of Mechanical and Electrical Engineering, Northeast Forestry University Harbin 150040
    2. College of Civil Engineering and Transportation, Northeast Forestry University Harbin 150040
  • Received:2021-12-28 Online:2023-08-25 Published:2023-10-16
  • Contact: Wenshu Lin

Abstract:

Objective: This study aims to construct stand canopy closure estimation models based on the extracted feature variables from the UAV-LiDAR point cloud data and the measured data of the sample plots, which would provide basic data and technical reference for rapid and accurate estimation of artificial forest canopy closure. Method: Taking the Urban Forestry Demonstration Base of Northeast Forestry University as the study area, the inversion of the forest closure for the artificial coniferous forests and broad-leaved forests was carried out based on the point cloud data obtained by multi-rotor UAV LiDAR. The height, intensity and canopy characteristic variables were calculated according to the three-dimensional coordinates and energy values of the point cloud, and the principal component analysis method was used to reduce the data dimension. Then, a stepwise regression procedure was conducted on the canopy closure obtained by the plant canopy analyzer and the processed variables, and the canopy closure estimation models for artificial coniferous forests and broad-leaved forests were established, respectively. Finally, the estimation models and inverse distance weight interpolation method were applied on the ArcGIS platform to perfom canopy closure inversion mapping. Result: Canopy characteristic variables had the most significant effect on the canopy closure estimation accuracy of coniferous forests, while intensity characteristic variables had the most significant effect on the estimation accuracy of broad-leaved forests. The canopy closure estimation accuracy of artificial broad-leaved forests (Adj R2 = 0.725, RMSE = 0.005 ) was superior to that of artificial coniferous forests (Adj R2 = 0.722, RMSE = 0.007 ). The canopy closure of the entire plot estimated by the estimation models and inverse distance weighted interpolation method ranged between 0.81 and 0.87, and the canopy closure of 10 testing points showed a high correlation with the measured canopy closure (r = 0.859). Conclusion: Combining multiple sets of LiDAR feature variables to estimate forest canopy closure can fully exploit the canopy structure characteristics contained in LiDAR data and improve the estimation accuracy.

Key words: UAV-LiDAR, canopy closure, characteristic variables, principal component analysis, stepwise regression

CLC Number: