Vegetation - Yosemite [ds200]

The United States Geological Survey (USGS) and National Park Service (NPS) formed the USGS-NPS Vegetation Mapping Program in 1994 to map the vegetation of National Park System units in accordance with the updated U.S. National Vegetation Classification (USNVC). In 1996, the Vegetation Inventory and Type Mapping Project of Yosemite National Park was initiated as a pilot project to assess how well existing data could be integrated in the classification. Aerial Information Systems, Inc. (AIS) was subcontracted by the primary contractor, Environmental Research Institute (ESRI), to form a team that would perform photinterpretation, data integration, preliminary classificaiton, field data collection, and accuracy assessment. Nature Serve and Yosemite National Park staff established study area boundaries. The mapping study area, consists of approximately 1,387,451 acres of Yosemite National Park and Devils Postpile National Monument as identified by Yosemite staff. Work was performed on the project between 1997 and 2003. In 1997, a preliminary vegetation classification was developed by Nature Serve/California State Heritage Program and USGS staff using existing datasets and a gradsect analysis was made to allocate field sampling points within the study area. These pre-existing data included the Weislander Data of 1935-1937, Natural Resources Inventory (NRI) Data of 1988-1993, and U.S Forest Service Upland and Riparian Classification Plots analysis by Don Potter in 1994 and 1998. The grandsect analysis entailed establishing the environmental variables most influential on Yosemite's vegetative diversity and then producing a spatial model of predicted vegetative diversity based on the environmental variables. A grid of plots known as Biophysical Units (BPUs) was then created. Unsampled BPUs were selected for field data collection with a focus on those which needed sampling for Yosemite's overall classification scheme and those which presented undefined signatures to photointerpreters. In Spring 1998, NatureServe ecologists developed a releve-based standardized field data collection protocol. Between the 1998 and 199 field seasons, Nature Serve staff sampled a total of 604 plots at the times when each plot's flowering phenology reached optimal sampling conditions and the most species would be identifiable. AIS photointerpreters jointly conducted field reconnaissance with USGS and NatureServe ecologists during the 199 field season and provided photo delineations of unsampled BPUs. Photointerpretation for the finalized map was completed by AIS between 2000 and 2002. CNPS under separate contract and in collaboration with CDFW VegCAMP developed the floristic vegetation classification used for the project. The floristic classification follows protocols compliant with the Federal Geographic Data Committee (FGDC) and National Vegetation Classification Standards (NVCS). Aerial imagery was collected in 1997 at a scale of 1: 5,860 to be interpreted for vegetation cover and serve as the base for attribute coding, both of which tasks were done by AIS. Each aerial photo was prepared with 23 cm x 23 cm frosted mylar overlay. Digital orthophoto quarter quadrangles (DOQQs) from 1987-1999 (black-and-white and infra-red) were used in combination with aerial imagery to identify control points. Mono Digitizing Stereo Digitizing (MDSD, Carto Instruments Incorporated, Seattle, WA) software used the control points and NatureServe's vegetation linework for data automation, automatically georeferencing each photo to the DOQQ with real-world coordinates. Digitized linework was then converted from MDSD outfile format to a coverage using ARC/INFO (Environmental Systems Research Institute, Inc., Redlands, CA).美国地质调查局（United States Geological Survey, USGS）与国家公园管理局（National Park Service, NPS）于1994年联合发起USGS-NPS植被制图项目，旨在依据更新后的《美国国家植被分类系统》（U.S. National Vegetation Classification, USNVC），对美国国家公园系统内的各园区开展植被制图工作。1996年，约塞米蒂国家公园植被清查与类型制图项目作为试点项目启动，以评估现有数据在该分类系统中的整合适配效果。主要承包商环境科学研究所（Environmental Research Institute, ESRI）将项目分包给Aerial Information Systems, Inc.（AIS），组建专项团队负责影像解译、数据整合、初步分类、野外数据采集与精度评估。Nature Serve和约塞米蒂国家公园工作人员共同划定研究区域范围：该制图研究区包含约塞米蒂国家公园与魔鬼柱国家纪念区共计约1387451英亩的土地，由约塞米蒂工作人员确认划定。项目整体执行周期为1997年至2003年。1997年，Nature Serve/加州州遗产项目与USGS工作人员依托现有数据集完成初步植被分类，并通过梯度样带（gradsect）分析划定研究区内的野外采样点位。本次依托的现有数据包括：1935-1937年的Weislander数据集、1988-1993年的自然资源清查（Natural Resources Inventory, NRI）数据，以及1994年与1998年由Don Potter完成的美国林务局高地与河岸分类样地分析。梯度样带分析首先筛选出影响约塞米蒂植被多样性的核心环境变量，随后基于这些变量构建植被多样性预测空间模型，并生成了被称为生物物理单元（Biophysical Units, BPUs）的样地网格。后续团队选取未采样的生物物理单元开展野外数据采集，重点覆盖约塞米蒂整体分类体系所需的采样单元，以及影像解译人员无法明确判别的单元。1998年春季，Nature Serve生态学家制定了基于样方记录（releve）的标准化野外数据采集规程。在1998年与1999年野外调查季期间，Nature Serve工作人员共计完成604个样地的采样，采样时机均选择在各该样地的开花物候达到最佳采样条件、多数物种均可被识别的时段。1999年野外调查季期间，AIS影像解译人员与USGS及Nature Serve生态学家共同开展野外踏勘，并完成了未采样生物物理单元的影像勾绘工作。最终制图所需的影像解译工作由AIS于2000年至2002年间完成。加州本土植物学会（California Native Plant Society, CNPS）通过独立合同，并与加州鱼类与野生动物部植被分类与制图项目（CDFW VegCAMP）合作，为本项目制定了植物区系植被分类方案。该分类方案严格遵循联邦地理数据委员会（Federal Geographic Data Committee, FGDC）与《国家植被分类标准》（National Vegetation Classification Standards, NVCS）的相关规程。项目采用1997年获取的1:5860比例尺航空影像开展植被盖度解译，并以此作为属性编码的基础，上述两项工作均由AIS完成。每张航空影像均配有23cm×23cm的磨砂聚酯薄膜覆盖片。1987-1999年获取的数字正射影像四分幅（Digital Orthophoto Quarter Quadrangles, DOQQs，包含黑白与红外波段）与航空影像结合使用，用于识别控制点。单视立体数字化（Mono Digitizing Stereo Digitizing, MDSD，华盛顿州西雅图Carto仪器公司）软件依托控制点与Nature Serve的植被线要素开展数据自动化处理，将每张影像自动地理配准至具备真实世界坐标的数字正射影像四分幅。最终，数字化后的线要素通过ARC/INFO软件（环境系统研究所，加利福尼亚州雷德兰兹）从MDSD输出格式转换为覆盖数据格式。