Above ground biomass density (AGBD) and cover for private reserves in Greater Kruger National Park, South Africa

Above Ground Biomass Density (AGBD) was modelled from ALOS2 ScanSAR data using field plot biomass and airborne LiDAR data as reference data. The study area includes the private reserves within Greater Kruger National Park, South Africa. The AGBD modeling was conducted after calculating the mean backscatter of 4 x 4 25m ScanSAR pixels and assigning the mean to a new 100 x 100m (1ha) grid. The modeling workflow involved (i) estimating AGBD within 1 ha field plots (ii) estimating AGBD with airborne LiDAR (ALS) canopy height model metrics (canopy cover and mean canopy height) inside 1ha grid cell and (iii) developing a model (Power Law)that predict AGBD from ScanSAR backscatter based on the widespread ALS AGBD reference data. The Power Law model was used for predicting fractional woody cover (Cover, decimal fraction) from the ScanSAR backscatter data using the ALS canopy cover as reference. Within each 1 ha grid cell, the LiDAR canopy cover reference variable was calculated by dividing the number of the 1 m canopy height model (CHM) pixels with heights above 0.5 m by the total number of CHM pixels.地上生物量密度（Above Ground Biomass Density, AGBD）以野外样地生物量与机载激光雷达（Light Detection and Ranging, LiDAR）数据为参考基准，基于ALOS2 ScanSAR数据构建反演模型。研究区域涵盖南非大克鲁格国家公园内的私有禁猎区。 在开展地上生物量密度建模前，需先计算4×4个25米分辨率ScanSAR像元的平均后向散射系数，并将该平均值赋予新生成的100×100米（即1公顷）网格单元。本次建模流程包含三个环节：(i) 估算1公顷野外样地内的地上生物量密度；(ii) 基于1公顷网格单元内的机载激光扫描（Airborne Laser Scanning, ALS）冠层高度模型（Canopy Height Model, CHM）指标——冠层覆盖度与平均冠层高度——反演地上生物量密度；(iii) 基于已广泛应用的机载激光扫描地上生物量密度参考数据，构建由ScanSAR后向散射系数预测地上生物量密度的幂律（Power Law）模型。 本研究同时以机载激光扫描冠层覆盖度为参考基准，利用该幂律模型基于ScanSAR后向散射数据预测木质植被覆盖占比（Cover，十进制小数形式）。在每个1公顷网格单元内，机载激光雷达冠层覆盖度参考变量的计算方式为：将冠层高度模型中高度大于0.5米的像元数量，除以冠层高度模型的总像元数量。