机载激光雷达数据辅助的县级森林平均蓄积量抽样估计方法

A Forest Mean Stock Volume Estimation Method in County Scale via Airborne LiDAR Data Assisted Sampling

  • 摘要: 机载激光雷达(ALS)数据的省级全覆盖为森林资源高精度监测提供了重要数据支撑。然而,在县级尺度上,如何有效整合ALS数据与县级加密样地调查数据,提升森林平均蓄积量的高精度抽样估计,目前研究仍较少。以山东省蒙阴县为研究区,利用ALS数据与森林资源加密样地数据,拟合非线性逻辑回归森林蓄积量估测模型,提出了采用ALS数据辅助县级森林平均蓄积量抽样估计的方法,比较了传统设计推断法、多种分层方法(包括基于ALS估测值进行分层)及基于ALS变量的模型辅助法在县域尺度森林平均蓄积量估计精度提升及不确定性量化中的潜力。研究结果表明,基于ALS变量的模型辅助法估测结果的标准误最低,分别为1.35 m3·hm-2(未引入坡度因子)和1.33m3·hm-2(引入坡度因子);其中引入坡度因子的蓄积量估测抽样精度最优(93.90%),相比传统设计推断法(90.28%、)精度提升约3%。多种分层方法中,基于ALS估测值的后分层法和引入坡度因子的双因子后分层法也取得了较低的标准误(1.39 m3·hm-2和1.37 m3·hm-2)和较高的抽样精度(93.77%和93.87%)。研究发现,采用ALS数据辅助抽样方法,可以有效地提高县域森林蓄积量的抽样估计精度;在地形复杂区域,加入坡度等地形因子进行分层设计,可以兼顾地形异质性,进而提高地形复杂区域的县域森林蓄积量的抽样估计精度。本文提出方法可为“优化森林资源调查方法、实现年度调查出数”的自然资源调查监测目标提供可行的解决方案。

     

    Abstract: Objectives: Airborne laser scanning (ALS) data have achieved full provincial coverage in parts of China, providing important support for high-precision forest resource monitoring. However, at the county scale, effective integration of ALS data with dense forest plot inventory data to improve sampling estimation of mean forest stock volume has received limited attention. Methods: We selected Mengyin County in Shandong Province as the study area and Nonlinear logistic regression models were fitted using ALS-derived variables and dense plot data to estimate plot-level forest stock volume. Traditional design-based inference, various stratification methods (including post-stratification based on ALS predictions and dual-factor post-stratification with slope), and model-assisted estimation using ALS variables (with and without slope) were compared. Performance was evaluated through standard error and sampling precision. Results: Model-assisted estimation based on ALS variables yielded the lowest standard errors: 1.35 m3·hm-2 (without slope) and 1.33 m3·hm-2 (with slope). The version incorporating slope achieved the highest sampling precision of 93.90%, representing around 3% improvement over traditional design-based inference (90.28%). Post-stratification using ALS predictions and dual-factor post-stratification (ALS + slope) also performed well, with standard errors of 1.39 m3·hm-2 and 1.37 m3·hm-2, and sampling precisions of 93.77% and 93.87%, respectively. The results revealed that incorporating slope effectively addressed terrain heterogeneity in complex areas. Conclusions: ALS-assisted sampling methods, particularly model-assisted estimation and targeted post-stratification, can substantially improve the precision of county-level mean forest stock volume estimation. These approaches offer feasible solutions for optimizing forest resource inventory methods and achieving the goal of annual high-frequency forest monitoring and reporting, especially in regions with complex topography.

     

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