Forest Health Protection Tree Species Metrics Stand Density Index

These data are a product of a multi-year effort by the FHTET (Forest Health Technology Enterprise Team) Remote Sensing Program to develop raster datasets of forest parameters for each of the tree species measured in the Forest Service’s Forest Inventory and Analysis (FIA) program. This dataset was created to support the 2013–2027 National Insect and Disease Risk Map (NIDRM) assessment. The statistical modeling approach used data-mining software and an archive of geospatial information to find the complex relationships between GIS layers and the presence/abundance of tree species as measured in over 300,000 FIA plot locations. Unique statistical models were developed from predictor layers consisting of climate, terrain, soils, and satellite imagery. Modeled basal area (BA) and stand density index (SDI) datasets for individual tree species were further post-processed to 1) match BA and SDI histograms of FIA data, 2) ensure that the sum of individual species BA and SDI on a pixel did not exceed separately modeled total for all species BA and SDI raster datasets, 3) derive additional tree parameters like quadratic mean diameter and trees per acre. With Landsat image collection dates ranging from 1985 to 2005, and a mean collection date for treed areas of 2002, and FIA plot data generally ranging from 1999 to 2005, the vintage of the base parameter datasets varies based on location, but can be roughly considered as 2002本数据集是FHTET（森林健康技术企业团队，Forest Health Technology Enterprise Team）遥感项目历经多年研发的成果，旨在为美国林务局森林资源清查与分析（FIA，Forest Inventory and Analysis）项目中调查的每个树种生成森林参数栅格数据集。本数据集的构建旨在支撑2013—2027年国家病虫害风险地图（NIDRM，National Insect and Disease Risk Map）评估工作。其统计建模方案采用数据挖掘软件与地理空间信息档案，探寻GIS图层与超过30万个FIA样地实测的树种存在度、丰度之间的复杂关联。研究团队基于气候、地形、土壤与卫星影像组成的预测因子图层，开发了专属统计模型。针对单一树种的模拟断面积（BA，basal area）与林分密度指数（SDI，stand density index）数据集还开展了三项后处理工作：1）匹配FIA数据的BA与SDI直方图分布；2）确保单个像元内各树种BA与SDI的总和，不超过所有树种合并后单独建模的总BA与总SDI栅格数据集的对应数值；3）推导二次平均直径、每英亩株数等额外森林参数。本数据集所用的Landsat（陆地卫星）影像采集时间跨度为1985年至2005年，其中林区影像的平均采集时间为2002年；而FIA样地数据的采集时段普遍集中于1999年至2005年。因此，基准参数数据集的基准年份因区域而异，但整体大致可视为2002年。