Vegetation classification and mapping project report, Grant-Kohrs Ranch National Historic Site

Rice, P.; Schweiger, E.; Gustafson, W.; Lea, C.; Manier, D.; Shorrock, D.; Frakes, B.; O'Gan, L.

The vegetation mapping effort at Grant-Kohrs Ranch National Historic Site (GRKO) is part of the National Park Service Inventory and Monitoring program and provides core or ‘baseline’ information that park managers need to effectively manage and protect park resources. This vegetation inventory was conducted in accordance with specified protocols and quality assurance standards. Data obtained through this inventory are compatible with other efforts, allowing for synthesis and analysis at broader levels. These data comply with standards and protocols of the USGS-NPS Vegetation Mapping Program. To effectively classify and map the wide range of vegetation within the mapping boundary required a multi-year approach and consisted of several linked phases: (1) vegetation classification using the U.S. National Vegetation Classification applied to field data collected by this project, (2) digital vegetation map production, (3) map accuracy assessment, and (4) revision of vegetation map and production of final products. The project was a cooperative effort between researchers from the University of Montana and National Park Service staff. Constant communication and coordinated efforts between these parties allowed for consistency in both accuracy and classification. The Grant-Kohrs Ranch National Historic Site is a working ranch commemorating the western open-range cattle industry that peaked in the 1890’s. The Ranch is located in a broad Rocky Mountain valley in west central Montana. The terrain consists of dry upland benches and the floodplain of the Clark Fork River. There are corrals, barns, and other ranch operation structures, as well as the original ranch house. The Ranch administrative boundary includes approximately 1,618 acres. The Vegetation Mapping project focused on 1599 acres of ranch holdings. A preliminary list of potential vegetation types was developed from previous descriptive vegetation inventory work in the area. Spectral analysis of aerial imagery from the National Agricultural Imagery Program was used in combination with soils data to delineate the boundaries of map unit polygons with apparently similar vegetation. Because of the small total area of the park and limited number of polygons it was decided to census every polygon as to community type rather than sample a subset of polygons and conduct a supervised classification. Map unit polygons were censused by field crews in 2006; crew members assigned each polygon to a vegetation or landcover type from the preliminary list. Accuracy assessment field work in 2007 collected data at 283 sample points which were used to assess the validity of the initial map assignments. The initial vegetation mapping recognized 40 plant community types and an additional 4 landcover types, but was estimated to have an overall accuracy of less than 29%. This low initial rate was attributed to reduced repeatability from the fine scale of both the original community types as well as the very small map unit polygons enabled by the mapping methodology. Furthermore, the complexity and prevalence of cultural vegetation types at GRKO required that the revision of types consider park management requirements as more important in some cases than mapping program standards. Consequently, the original types were aggregated into 29 final map classes representing 22 USNVC plant associations, 3 park-specific vegetation types, and 4 landcover classes. This consolidation resulted in a 62.5% accuracy rate (90% confidence interval 57.6% to 67.5%), Map classes were also assigned to five Ecological Systems and one equivalent level group; this level of grouping represents the GRKO vegetation with an overall map accuracy of 84.1% (90% confidence interval 80.3% to 87.9%). The uplands within GRKO are primarily vegetated by bunchgrass types in the blue bunch wheat grass (Pseudoroegneria spicata) Herbaceous Alliance, with needle and thread – blue grama – threadleaf sedge (Hesperostipa comata - Bouteloua gracilis

Vegetation classification and mapping project report, Grant-Kohrs Ranch National Historic Site

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