为探索基于哨兵2号(Sentinel-2)数据构建主要林分因子预估模型,估计乔木林小班因子的现实可行性,利用北京市1 500个乔木林样地的地面实测数据和光谱特征参数,采用误差变量联立方程组方法,构建针叶林、硬阔林、软阔林3种主要森林类型的8项林分因子预估模型,包括平均胸径(D)、平均树高(H)、平均优势高(H_d),以及每公顷株数(N)、断面积(G)、蓄积量(V)、生物量(B)和碳储量(C);将全市乔木林小班按25 m×25 m网格单元提取光谱特征参数,利用所构建8项林分因子预估模型,完成对所有乔木林小班因子的估计。结果表明:1)对估计主要林分因子贡献最大的光谱特征参数是短波红外波段1反射率(B11)和短波红外波段2反射率(B12),其次是红边波段1反射率(B5)和比值植被指数(RVI);2)所构建的3种主要森林类型8项林分因子预估模型,自检和交叉检验的平均预估误差(E_MP)均在10%以内;3)根据模型反演得出的乔木林小班蓄积量累计值,与全市综合监测得到的森林蓄积量相比仅差-1.74%,在抽样调查允许误差范围内。所建北京市3种主要森林类型的8项林分因子预估模型,可用于对全市乔木林小班主要林分因子的估计;基于哨兵2号光谱特征参数构建的主要林分因子预估模型,其预估精度基本能满足森林资源调查监测的技术要求,可在生产实践中应用。

In order to explore the feasibility of establishing main stand characteristics models based on Sentinel-2 data to estimate the factors of forest patches,the ground plot measured data and spectral characteristic metrics of 1 500 forest plots in Beijing were used to develop prediction models of three major forest types through the error-in-variable simultaneous equations.The models involve eight main stand characteristics,including mean DBH,mean height,dominant height,stem number,basal area,stock volume,biomass and carbon storage.Additionally,based on the spectral characteristic parameters extracted by 25 m×25 m grid cells within the forest patches in Beijing,the eight prediction models were used to estimate main stand characteristics of all forest patches.The results showed:1)The spectral characteristic metrics of Sentinel-2 that contributed the most to the estimation of main stand characteristics were B11 and B12(short wave infrared 1 and 2 band reflectance),followed by B5(red-edge 1 band reflectance)and RVI(Ratio Vegetation Index);2)The mean prediction errors(MPEs)of eight main stand characteristics models of three major forest types were less than 10%,either self-validation or cross-validation;3)The cumulative value of stock volume in all forest patches estimated by the volume models is only -1.74% lower than that obtained by the integrated monitoring of the municipality,which was within the allowable error range of sampling survey.The eight prediction models of three major forest types can be used to estimate the main stand characteristics of forest patches in Beijing;and the prediction accuracy of the main stand characteristics models based on spectral characteristic parameters of Sentinel-2 can almost meet the technical requirements of forest resource inventory and monitoring,then can be applied in practice.