Vegetation Information for the Lake Roosevelt National Recreation Area Vegetation Inventory Project

Lake Roosevelt National Recreation Area (LARO) encompasses a portion of Lake Roosevelt; a large reservoir formed by the Grand Coulee Dam and associated uplands in northeast Washington State. The reservoir, which inundates portions of the Columbia River, the Spokane River, and other rivers and streams encompasses about 100,585 acres (40,705 ha) stretching northwards from the dam to almost the Canadian border. The National Park Service (NPS) manages long, predominately linear strips of land along the north, east and southern portions of the reservoir. Contained in these lands are many significant cultural and recreational resources in addition to a unique mix of native and semi-native vegetation. Trending from north to south, LARO marks a transition zone between the desert-like Columbia Basin Plateau to the south and the slightly wetter Okanogan Highlands to the north. The vegetation follows this pattern with wetter conifer forest prevalent in the north gradually giving way to drier shrub-steppe vegetation in the south. Intermixed are distinctive riparian and shoreline shrub and woodlands and stands of non-native plant species. To better understand the plant community distribution at LARO, the NPS Vegetation Inventory Program (NVIP) funded an effort, beginning in 2006, to inventory and document (map) the vegetation. The Upper Columbia Basin Inventory and Monitoring Network (UCBN) coordinated the LARO vegetation inventory effort as part of a network-wide project. A four-year, four-phase program was initiated to complete the tasks of sampling, classifying, and mapping the vegetation types within LARO. Phase-one, directed by UCBN staff in conjunction with Northwest Management Incorporated (NMI) and the Idaho Conservation Data Center (ICDC) resulted in the plant association and alliance classification using the National Vegetation Classification System (NVCS). Classification was based on new, 2007 sampling efforts resulting in 431 representative classification plots and 47 observation points located within LARO. Analysis of the classification plot data by ICDC ecologists occurred in late 2008. Through this process 81 distinct plant associations were identified. Vegetation descriptions and a field key for each association are included as appendices to this report. Phase-two, directed by NMI and Cogan Technology, Inc. (CTI) resulted in the digital vegetation map and geodatabase. Mapping was conducted primarily on 2009 National Aerial Imagery Program (NAIP) products supplemented by 2002 imagery obtained from the Bureau of Reclamation (BOR). Interpreting the vegetation-specific signatures from the new imagery, CTI reliably discerned 33 vegetation, 18 land use/land cover, and five geology/sparse vegetation map units. The mapping process used primarily manual digitizing of the homogenous photo-signatures supported by on-site verification. All interpreted data were converted to Geographic Information System (GIS) databases using ArcGIS© software. The final map layer contains vegetation, land-use, and geologic exposure polygons with corresponding map class, NVC, and modifier attributes.