3.6.1.20 Rare, Threatened, and Endangered Plant Species

Common Name Scientific Name Native to Wyoming State or Carbon County List

Russian olive Elaeagnus angustifolia No State of Wyoming

Halogeton

Perennial pepperweed Halogeton glomeratus No Carbon County

Lepidium latifolium No State of Wyoming

Wyeth lupine Lupinus wyethii Yes Carbon County Plains pricklypear Opuntia polyacantha Yes Carbon County Sources: Carbon County Weed and Pest 2020; HDR 2022d; Wyoming Weed and Pest Council 2020.

Of these 12 species, cheatgrass was the most prevalent, occurring throughout the botanical study area, especially in disturbed areas along roads and in livestock grazing plots. The two-track road to the proposed upper reservoir had the highest concentration of noxious weed species found during surveys including Wyeth lupine, Canada thistle, hoary cress, Russian knapweed, bull thistle, and diffuse knapweed. Plains pricklypear, a Carbon County noxious weed is prevalent throughout the study area. It was observed mostly along the transmission line corridor and throughout the eastern portion of the study area. The remaining noxious weed species were primarily found along Hanna Leo Draw Road (halogeton and perennial pepperweed) and in the vicinity of Difficulty Creek (another occurrence of hoary cress, plumeless thistle, and Russian olive). Wyeth lupine is native to Wyoming, and although designated as a noxious weed under the Wyoming Weed & Pest Control Act, it is not ecologically the same as the other non-native noxious weeds. The location of these populations is included in Appendix E.

3.6.1.20 Rare, Threatened, and Endangered Plant Species

A list of ESA-listed plant species potentially occurring in the botanical study area was prepared using the USFWS IPaC website (USFWS 2022a). This list returned records and/or potential habitat for three ESA-listed plant species: blowout penstemon (Penstemon haydenii), Ute ladies’-tresses (Spiranthes diluvialis), and western prairie fringed orchid (Platanthera praeclara). No critical habitat for any ESA-listed species occurs in the botanical study area (USFWS 2022a). Based on the results of the Special-Status Plants and Noxious Weeds Study, only Ute ladies’-tresses, an ESA-threatened species, was determined to have potential to occur based on suitable habitat (HDR 2022d).

A habitat assessment for Ute ladies’-tresses was conducted in May 2021, and further refined in August 2021 concurrent with the Aquatic Resources Inventory Study (HDR 2022a) and following the 1992 Interim Survey Requirements for Ute Ladies’-tresses Orchid (Spiranthes diluvialis) – Revised 2017 (USFWS 2017). The Ute ladies’-tresses habitat assessment for the 2022 updated study area was conducted August 3 and August 4, 2022, in concurrence with the wetland delineation effort for Aquatic Resources Inventory Study (HDR 2022a). This aspect of the botanical study required a unique survey area from the standard botanical study area. The Ute ladies’-tresses habitat assessment determined that 23.54 acres of habitat occurs in the Ute ladies’-tresses habitat survey area, 21.44 acres of

which occurs on private property with the remaining 2.34 acres on land managed by the BLM. This habitat almost exclusively occurs along perennially flowing stream banks and most of the habitat is disturbed to some extent from livestock grazing and trampling as well as hay production. In 2021, one individual of ladies’-tresses (Spiranthes sp.) was observed but it was desiccated and not in condition to enable identification to species. In 2022, the individual was examined again, and determined not to be Ute ladies’ -tresses.

Maps of potential Ute ladies’-tresses habitat within the botanical study area are included in Appendix E. Most of the suitable habitat occurs in irrigated hay pastures that were inundated during the August 2022 surveys.

The BLM maintains a list of sensitive plant species for Wyoming (BLM 2010), and four species were determined to have potential to occur in the botanical study area. These four species are Cedar rim thistle (Cirsium aridum), limber pine (Pinus flexilis), persistent sepal yellowcress (Rorippa calycina), and Rocky Mountain twinpod (Physaria saximontana ssp. saximontana). The results of the study found occurrences of limber pine and persistent sepal yellowcress in the botanical study area that are described below and are depicted in Appendix E. The study also determined that Cedar rim thistle and Rocky Mountain twinpod would not have potential to occur in the botanical study area based on a lack of suitable habitat (HDR 2022d). Please see Table 3.6-3 below for details.

Table 3.6-3. BLM Sensitive Plant Species in the Botanical Study Area

Species Distribution and Habitat Requirements

Suitable Habitat in the Botanical Study Area

Cedar rim thistle (Cirsium aridum) This species occurs on barren chalky hills, gravelly slopes, and fine-textured shaley draws and fans, often on mid to upper slopes. Soils are derived from whitishgray sandstone, chalk, tuffaceous colluvium, or clay substrates, often associated with the Split Rock and White River formations recorded in the upper Green River and Granite Mountains (Carbon and Sublette Counties). Flowers bloom late June through August. No

Limber pine (Pinus flexilis) This species occurs in montane forests. Wyoming populations are on a variety of wind-exposed settings on ridges, outcrops, breaks and slopes, from topographic breaks in basins, to foothills, and to timberline. It has the largest elevational range of any conifer in the Rocky Mountains. Yes

Persistent sepal yellowcress (Rorippa calycina) This species is found primarily along moist sandy to muddy banks of streams, stock ponds, and man-made reservoirs near the high-water line. It occurs mostly on semi-disturbed or recently flooded openings in small inlets or bays. Occasional populations can also be found in openings in grassy stream banks, and on the banks of small playa lakes. Total vegetative cover at all Yes