下载中心
优秀审稿专家
优秀论文
相关链接
首页 > , Vol. , Issue () : -
摘要

森林冠层高度作为森林垂直结构的关键参数,其精准估测在碳循环与森林地上生物量(Above-Ground Biomass,AGB)研究中发挥着不可或缺的作用。随着遥感技术的不断发展,多源遥感数据为大尺度森林监测中冠层高度估测提供了新的可能性。本研究以中国东北地区(Northeast China,NEC)为研究区域,提出了一种结合随机森林(Random Forests, RF)和经验贝叶斯克里金(Empirical Bayesian Kriging, EBK)方法的模型(RF-EBK),用于区域尺度森林冠层高度的估测。该模型基于星载激光雷达ICESat-2(Ice, Cloud, and Land Elevation Satellite-2)提供的离散冠层高度数据(ATL08)、Landsat 8 OLI影像、航天飞机雷达地形测绘任务(Shuttle Radar Topography Mission,SRTM)地形数据以及森林冠层覆盖数据(CATCD),首先采用基于交叉验证的递归特征消除方法(Recursive Feature Elimination-Cross Validation,RFE-CV)筛选多源遥感数据中提取的特征因子,通过RF模型进行森林冠层高度估测,并计算测试集的估测残差。基于估测残差的空间自相关性,利用EBK方法对估测残差进行建模,得到研究区域空间连续残差插值结果,并对RF估测结果进行残差校正,从而有效提高模型的估测精度,最终实现中国东北地区2023年30m森林冠层高度的高精度估测。结果表明,森林冠层覆盖在冠层高度估测中的重要性较高;在模型精度方面,RF-EBK模型相比单独使用RF模型具有更优的估测性能,验证集R2提高了59.5%,RMSE和rRMSE降低了27%。此外,使用在研究区域内6个采样点采集的无人机激光雷达(Unmanned Aerial Vehicle Laser Scanning, ULS)数据,对RF-EBK模型估测结果进行精度验证, R2为0.69,RMSE为1.65 m,rRMSE为7.81%。综上所述,RF-EBK模型能够实现区域尺度森林冠层高度的高精度估测,为中国东北地区的精准营林管理和可持续森林资源经营提供了有效的技术支持。
Forest canopy height, as a key parameter reflecting the vertical structure of forests, is essential for understanding the structure and function of forest ecosystems. Accurate estimation of canopy height is critically important for carbon cycle assessments, above-ground biomass (AGB) estimation, and ecosystem health monitoring. With the continuous advancement of remote sensing technologies—particularly the integration of LiDAR and optical remote sensing data—the potential for estimating forest canopy height at regional scales has become increasingly prominent, making it a current research hotspot in forest resource monitoring. This study focuses on Northeast China (NEC) and proposes a hybrid model that integrates Random Forest (RF) and Empirical Bayesian Kriging (EBK), referred to as the RF-EBK model, aiming to enhance the accuracy and robustness of regional-scale canopy height estimation. The model incorporates discrete canopy height data from the spaceborne LiDAR ICESat-2 (ATL08), Landsat 8 OLI imagery, Shuttle Radar Topography Mission (SRTM) elevation data, and forest canopy cover data (CATCD).Initially, a recursive feature elimination method with cross-validation was employed to select optimal variables, reduce redundancy, and improve the model"s generalization ability. The RF model was then used to produce initial canopy height estimates, and residuals were calculated using a test dataset. Given the spatial autocorrelation of the residuals, the EBK method was applied to spatially model and interpolate them, generating a continuous residual surface across the study area. This residual surface was used to correct the RF predictions, effectively improving estimation accuracy. Ultimately, a high-accurate forest canopy height map at a 30 m resolution for NEC in 2023 was produced. The results show that forest canopy cover was the most important variable in the model. Among topographic factors, slope, elevation, and aspect were also highly influential, reflecting the significant role of terrain in vegetation type and growth conditions. In terms of optical remote sensing features, the original Landsat 8 OLI bands B2, B4, and B7 exhibited high importance. Moreover, texture features derived from bands B3, B6, and B7 (i.e., B3_savg, B6_savg, and B7_savg) were more important than the original bands, underscoring the value of incorporating spatial texture features for canopy height estimation. The Tasseled Cap Greenness (TCG), indicative of canopy cover and vegetation health, also showed strong predictive power. In terms of model performance, the RF-EBK model significantly outperformed the standalone RF model by effectively mitigating the overestimation of low canopy heights and underestimation of high canopy heights. After residual correction, the coefficient of determination (R2) on the validation set increased by 59.52%, while the RMSE and rRMSE decreased by 27%. Furthermore, canopy height measurements extracted from unmanned aerial vehicle laser scanning (ULS) data collected from six sites were used as reference data for model validation. The results showed that the RF-EBK model achieved high accuracy, with an R2 of 0.69, RMSE of 1.65 m, and rRMSE of 7.81%. In conclusion, the RF-EBK model provides a reliable approach for high-accurate estimation of forest canopy height at the regional scale and offers robust technical support for precision silviculture and sustainable forest resource management in Northeast China.