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Scientia Silvae Sinicae ›› 2023, Vol. 59 ›› Issue (4): 88-99.doi: 10.11707/j.1001-7488.LYKX20210712

• Research papers • Previous Articles     Next Articles

A Method for Estimating Subtropical Forest Stock by Combining Remotely Sensed Forest Age Factors

Xiaocheng Zhou1(),Tingting Huang1,Yuan Li1,Xiangxi Xiao2,Hongru Zhu3,Yunzhi Chen1,Zhiqing Feng4   

  1. 1. Local Joint Engineering Research Center of Satellite Geospatial Information Technology Key Laboratory of Spatial Data Mining and Information Sharing of Ministry of Education, Fuzhou University Fuzhou 350108
    2. Fujian Academy of Forestry Fuzhou 350012
    3. Fujian Forest Inventory and Planning Institute Fuzhou 350003
    4. Fujian Jinsen Forestry Co.Ltd. Jiangle 353300
  • Received:2021-09-17 Online:2023-04-25 Published:2023-07-05

Abstract:

Objective: The XGBoost algorithm was applied to establish a remote sensing factor-stock volume model containing forest age, to evaluate the effectiveness of combining the remote sensing estimated forest age factor with the remote sensing factor to improve the accuracy of forest volume estimation, and to provide a new idea and method to achieve efficient, fast and accurate forest volume estimation on a large scale. Method: Taking Jiangle County, Fujian Province as a case, firstly, based on the time-series Landsat images from 1987—2016, combined with the measured stock volume data of subcompartment of forest resource inventory and planning, the LandTrendr forest disturbance and restoration monitoring algorithm was used to monitor the annual stand turnover disturbance and estimate the forest age in the disturbance area; Second, based on the GF-1 image spectral, texture, and topography features, the recursive feature elimination random forest algorithm (RFE-RF) to estimate the forest age in the non-disturbed area; Finally, the GF-1 image spectral and texture factors were combined with the forest age factor by the extreme gradient boosting algorithm (XGBoost) to estimate the forest stock of the study area. The accuracy of forest stock estimation with and without the forest age factor was compared to further verify the importance of remote sensing forest age factor to improve the accuracy of forest stock estimation. Result: The error of forest age obtained by using LandTrendr algorithm in the forest disturbance area was only 1-2 years, and the accuracy of forest age estimation was significantly better than that of the traditional estimation of forest age using remote sensing factors (error of 4-12 years). When only conventional remote sensing factors were used to estimate the volume, the model R2 of XGBoost was 0.59 and the average RMSE was 30.72 m3·hm?2,the rRMSE was 16.46%; after adding the forest age factor, the model R2 increased to 0.73, the average RMSE decreased to 23.73 m3·hm?2, the rRMSE was 13.26%, and the average overall accuracy of the stock volume estimation improved by about 10.4% to 84.4%. Conclusion: The accuracy of the XGBoost algorithm combined with the forest age parameter for estimating the stock volume is close to the requirements of the relevant regulations of forest resources survey, which can provide important technical support for the rapid survey and assessment of forest resources on a large scale.

Key words: forest stock volume, forest age, time series remote sensing, RFE-RF, XGBoost

CLC Number: