Each polygon in this feature class has been assigned a name that corresponds with the dominate geographic feature in that location. One exception to this are the relatively small Thermal Areas PCAs, which are named for the presence of hydro thermal features. Names can be found in the field PCA_nam, Priority Conservation Area Name. A description of the vegetation, reason for selection and the polygon boundary delineation methods used for each PCA follow:

Northern Range: The Northern Yellowstone Cooperative Wildlife Working Group was formed to cooperatively preserve and protect the long-term integrity of the northern Yellowstone winter range for wildlife species by increasing scientific knowledge of the species and their habitats, promoting prudent land management activities, and encouraging an interagency approach to answering questions and solving problems. Members are the Yellowstone National Park, Custer Gallatin National Forest, Montana Fish, Wildlife and Parks, and the Northern Rocky Mountain Science Center (U.S. Geological Survey). The Working Group conducts approximately annual counts and classifications (age, sex) of the northern Yellowstone elk population that spends winter on approximately 1,530 km2 of grasslands and shrub steppes along the northern boundary of Yellowstone National Park and nearby areas of southwest Montana. This area is often referred to as the ‘northern range.’ Most northern Yellowstone elk migrate seasonally, moving from higher-elevation summer ranges throughout the park to the winter range in the northern portion of the park and nearby areas of southwest Montana. The population expanded its winter range north of the Park and into Paradise Valley, Montana, during the 1970s and 1980s in response to increasing elk abundance, changes in structure and timing of hunter harvests, and protection of winter ranges outside the Park. The winter range for northern Yellowstone elk consists primarily of foothills and valley bottoms along the Gardner, Lamar, and Yellowstone river watersheds. The climate is characterized by short cool summers and long cold winters. Mean annual precipitation varies from about 25 to 35 centimeters as elevation increases from 1,500 meters in river drainages to 3,400 meters on mountains. Average snow-water equivalents (i.e., amounts of water in snow) range from 2 to 30 centimeters along this elevation gradient. Native vegetation is primarily steppe or shrub steppe (primarily Idaho fescue Festuca idahoensis, blue-bunch wheatgrass Pseudoroegneria spicata, and big sagebrush Artemsia tridentata) with stands of montane forest (primarily lodgepole pine Pinus contorta and Douglas fir Pseudotsuga menziesii) at higher elevations and woody riparian communities (primarily aspen Populus tremuloides and willow Salix sp.) in the valleys. Reference: White, P. J., K. M. Proffitt, and T. O. Lemke. 2012. Changes in elk distribution and group sizes after wolf restoration. American Midland Naturalist 167:174-187. PJ White Supervisory Wildlife Biologist pj_white@nps.gov

Gallatin Conservation Area: The Gallatin Range is known to be of high conservation value based on forests containing whitebark pine, rare alpine plants that occur primarily on calcareous substrates, and generally intact floral communities or flora with a high component of native plants species that have not been invaded by nonnative species (e.g., cheatgrass, alyssum, clover, etc.). The polygon for this conservation area was initially defined by vegetation above 8,000 feet. Thereafter, expert opinion by the park Botanist (Heidi Anderson) refined the southern end of the polygon edited to omit areas where rare plant populations no longer occur and/or lack of whitebark pine. Heidi Anderson Park Botanist Heidi_Anderson@nps.gov

Hayden Conservation Area: Hayden Valley is a physical valley dominated by sagebrush species Artemisia tridentata ssp vaseyana (mountain big sage) where the soils are drier and A. cana (silver sage) near the river and tributaries. The understory species in the big sage are Idaho fescue, oat grass, and upland sedges. Silver sage understory is hair grass, sticky geranium, and lupine. Other than the road corridor, Hayden Valley is largely free of exotic and invasive species. Because of the high value of intact, native flora, Hayden Valley has been selected as a location to concentrate management efforts directed at preserving these high-quality plant communities. Increasing visitation, off-trail travel, high-use pullouts and wildlife viewing locations have the potential to bring numerous invasive species to the Valley, establishing and spreading. Increased invasive species and novel plant communities are expected under all of the climate change scenarios, therefore we must collect spatial and temporal baseline community data to be used to direct management activities to preserve, protect, and understand the floristic resources. The initial polygon delineating the conservation area was drawn by using aerial imagery (ESRI World Imagery Service layer 2021). . While sagebrush is in the understory of the forest type, the conservation area was selected on the tree-free sagebrush areas which are easily detected on imagery; the north, west, and south boundaries follow the tree line and exclude the thermal areas. The east boundary is defined by the Yellowstone River as represented in All Rivers in Yellowstone National Park, Wyoming, Montana, Idaho unpublished dataset created by the Spatial Analysis Center, Yellowstone National Park 1998. While Hayden Valley technically exists on the eastern side the river, access to these areas is extremely difficult and has little anthropogenic disturbance. Stefanie Wacker, Vegetation Ecologist stefanie_wacker@nps.gov

Bechler Conservation Area: Heidi Anderson Park Botanist The Bechler area is the wettest area of the park, contains numerous waterfalls, and is characterized by a variety of vegetation and features that include thermal wetlands, thermal features, wetland meadows, spruce fir forest, lodgepole forest, and rare plants. Some of these rare plants do not occur anywhere else in the park and, in some cases, do not occur elsewhere in the state of Wyoming. The initial polygon delineating this conservation area was defined in the paper Climate Zone Delineation: Evaluating Approaches for Use in Natural Resource Management (Tercek et al. 2012, http://climateanalyzer.science/Tercek_et_al_climate_zonation.pdf ). The polygon boundary was further edited through expert opinion of the park Botanist (Heidi Anderson) to follow HUC 7 watershed boundaries (USGA NHD, Watershed Boundary Dataset, http://prd-wret.s3-us-west-2.amazonaws.com/assets/palladium/production/atoms/files/wy_hu12.txt), topographic features, and the boundaries of the habitat layer (sacgisdata.DBO.YELL_Habitat_Types, Yellowstone National Park, Wyoming, Montana, Idaho unpublished dataset created by the Spatial Analysis Center, Yellowstone National Park 1988) ) and to include locations of rare plants from Yellowstone’s rare plant database (unpublished data). Heidi Anderson Park Botanist Heidi_Anderson@nps.gov

Storm Point Conservation Area: Storm Point and adjacent areas are home to the last remaining population of the Yellowstone Sand Verbena (Abronia ammophila), a Yellowstone endemic, that occurs nowhere else in the world. The polygon for the Storm Point conservation area was delineated to include the area where the plants occur (as identified in Yellowstone’s rare plant layer, unpublished data) as well as habitat where it was known to occur and from which it has been extirpated. The polygon also includes vegetation that is not habitat for sand verbena (i.e., sagebrush steppe, forest), but is important for informing management actions (e.g., the use of Storm Point Trail). The southern boundary of the polygon is defined by Yellowstone Lake, the eastern boundary is defined by the existing population and the area that could affect the population, the western boundary is defined by the mouth of Yellowstone River, and the northern boundary is the Grand Loop Road (yell_roads Yellowstone National Park, Wyoming, Montana, Idaho unpublished dataset created by the Spatial Analysis Center, Yellowstone National Park Date Unknown) . Heidi Anderson Park Botanist Heidi_Anderson@nps.gov

Thermal Vegetation Conservation Areas: The thermal areas in Yellowstone are often habitat for rare plants, including all three of the park’s endemic species and a bryophyte that has its next-closest population in South America. Thermal areas are often highly impacted by weeds. The polygon for this conservation area was developed based on expert knowledge of the thermal areas by park Botanist Heidi Anderson and researcher Mike Tercek. They conducted a GIS analysis to identify the intersection of the rare plant layer, which is a data layer of rare plants known to occur in the park, and the parks thermal layer (sacgisdata.DBO.YELL_inventoried_thermal_features, Yellowstone National Park, Wyoming, Montana, Idaho unpublished dataset created by the YCR Geology Program, Yellowstone National Park 2018) ) to identify the locations of high plant conservation value. Some of the plant records in the rare plant layer were identified through formal surveys and others were digitized from herbarium records. Anderson and Tercek then looked the resulting layer and included other locations ones that likely have undocumented rare plants or they believed to have high conservation value. The plant species mapped in the geothermal areas range from the highly vulnerable and endemic (i.e., occurs only in Yellowstone) Agrostis rossiae (Ross’ Bentgrass) to other species that are not rare from a global perspective, but that occur only in thermal habitats at this latitude (e.g., Eleocharis flavescens var. thermalis). The species included for consideration when defining this polygon include: Eriophorum chamissonis, Lonactis alpina, Elodea nuttallii, Agrostis rossiae var. rossiae, Agrostis rossiae var. pauzhetica, Eleocharis flavescens var. thermalis, Juncus tweedyi, Antennaria flagellaris, Eriogonum umbellatum var. cladophorum, Juncus filiformis, Gaura parviflora, Cyperus squarrosus, Juncus tenuis, Castilleja exilis, Drosera anglica, Carex cusickii, Botrychium simplex, Botrychium simplex var. simplex, Carex echinata ssp. echinata, Carex livida, Cryptantha spiculifera, Carex parryana var. parryana, Eriophorum viridicarinatum, , Botrychium multifidum, Centaurium exaltatum, Juncus interior, Eleocharis elliptica, Castilleja gracillima, Carex buxbaumii, Agoseris lackschewitzii, Heterotheca depressa, Erigeron pumilus ssp. intermedius, Hierochloe odorata, Eleocharis rostellata, Epipactis gigantea, Guara parviflora, and Achnatherum xbloomer. Heidi Anderson Park Botanist Heidi_Anderson@nps.gov

Avalanche, Top Notch, Washburn and Trident Conservation Areas: These alpine conservation areas were created to support the Vegetation and Resource Management Operations Strategic Plan under development in 2020. Alpine vegetation and soils occur above tree line and are shaped by extreme conditions. Alpine plants are subject to and adapt to high winds, low temperatures, scouring and burial by snow and ice, solar radiation, and a short growing season. Plants are small, but flowering plants may have full-size blossoms. The plants grow slowly and often have leaves resistant to cold and desiccation, including hairs on stems and leaves that provide wind protection, and some plants have red-colored pigments that convert the sunshine into heat. Cushion plants hug the ground and may have long tap roots into the rocky soil and grasses and sedges may occur where soil is well-developed. Alpine communities are sensitive to changes in weather and climate, air quality that affects soil nutrients available to plants, and human and natural disturbance. These polygons were selected for biological value, including ecological significance (e.g., rare and/or vulnerable species and habitat) and integrity (e.g., level of naturally functioning ecosystem processes) as well as by current and future threats to these areas. Alpine areas chosen included the Trident, Mount Washburn, Avalanche Peak, and Top Notch Peak, and the polygons for these areas were extracted from the non-forested, alpine class of the Yellowstone National Park Habitat Types GIS layer (sacgisdata.DBO.YELL_Habitat_Types, Yellowstone National Park, Wyoming, Montana, Idaho unpublished dataset created by the Spatial Analysis Center, Yellowstone National Park 1988). These areas have high integrity with a large relatively intact vegetative community, some visitor disturbances, and in the case of the Trident, there are 3 rare plants that are known only at this location in the park. Hillary Robison, Deputy Chief of Yellowstone Center for Resources hillary_robison@nps.gov