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林业科学 ›› 2023, Vol. 59 ›› Issue (4): 88-99.doi: 10.11707/j.1001-7488.LYKX20210712

• 研究论文 • 上一篇    下一篇

结合遥感林龄因子的亚热带森林蓄积量估算方法

周小成1(),黄婷婷1,李媛1,肖祥希2,朱洪如3,陈芸芝1,冯芝淸4   

  1. 1. 福州大学空间数据挖掘与信息共享教育部重点实验室 卫星空间信息技术综合应用国家地方联合工程研究中心 福州 350108
    2. 福建省林业科学研究院 福州 350012
    3. 福建省林业调查规划院 福州 350003
    4. 福建金森林业股份有限公司 将乐 353300
  • 收稿日期:2021-09-17 出版日期:2023-04-25 发布日期:2023-07-05
  • 基金资助:
    福建省科技厅对外合作项目(2022I0007);福建省科技厅高校产学合作项目(2022N5008);福建省林业科技攻关项目(2021FKJ01)。

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

摘要:

目的: 应用XGBoost算法建立包含林龄的遥感因子-蓄积量模型,评价遥感估算的林龄因子与遥感因子相结合提高森林蓄积量估算精度的有效性,为实现高效、快速、精准的大范围森林蓄积量估算提供一种新的思路和方法。方法: 以福建省将乐县为研究示范区,首先,基于1987—2016年时序Landsat影像,采用LandTrendr森林干扰与恢复监测算法监测年度林分更替干扰并估算干扰区林龄;然后,基于GF-1号影像光谱、纹理、地形等特征,采用递归特征消除的随机森林算法(RFE-RF)估算非干扰区林龄;在此基础上,结合GF-1影像光谱、纹理因子和森林资源二类调查小班实测蓄积量数据,采用极端梯度提升算法估算研究区森林蓄积量。对比有无林龄因子的森林蓄积量估算精度,进一步验证遥感林龄因子对提高森林蓄积量估算精度的重要性。结果: 采用LandTrendr森林干扰与恢复监测算法获得的干扰区林分林龄误差仅1~2年,林龄估算精度明显优于传统利用遥感因子估算的林龄精度(误差4~12年)。仅采用常规遥感因子估算森林蓄积量时,XGBoost模型决定系数(R2)为0.59,平均均方根误差(RMSE)为30.72 m3·hm?2,相对均方根误差(rRMSE)为16.46%;加入林龄因子后,模型R2提高至0.73,平均RMSE减少至23.73 m3·hm?2,rRMSE为13.26%,森林蓄积量估算平均总体精度约提高10.4%,达84.4%。结论: 相比仅采用常规遥感因子估算森林蓄积量,应用XGBoost算法建立包含林龄的遥感因子-蓄积量模型,其估算精度接近森林资源调查相关规定要求,可为大范围亚热带森林资源快速调查评估提供重要技术支持。

关键词: 森林蓄积量, 林龄, 时序遥感, 递归特征消除的随机森林, 极端梯度提升算法

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

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