3.6.1.21 Limber Pine

Species Distribution and Habitat Requirements

Suitable Habitat in the Botanical Study Area

sites averages 5-10 percent (but can reach 25 percent in some areas). Regional endemic of the Wyoming Basins Ecoregion and historic records on the Yellowstone River in south-central Montana and western North Dakota. Flowers late May to August but can be extended into mid-October.

Rocky Mountain twinpod (Physaria saximontana var. saximontana) This species occurs on ridges and slopes on sandy, gravelly, and rocky soils of limestone, red sandstone, or clay. The vegetation is mainly sparsely vegetated cushion plant communities in sagebrush grasslands and open limber pine and Utah juniper woodlands. State endemic found in the southern Bighorn and Wind River Basins, and foothills of the Absaroka, Owl Creek and Wind River Ranges (Fremont, Hot Springs, and Park Counties). Specimens from Carbon and Natrona Counties are under review. Flowers bloom May through late June. No

Sources: WYNDD 2022, HDR 2022d. 3.6.1.21 Limber Pine

Limber pine is a primary constituent of Rocky Mountain Foothill Limber Pine-Juniper Woodland which is mapped in the Habitat Assessment and Rare, Threatened, and Endangered Species Evaluation Study Report (HDR 2022c). This habitat occupies approximately 622 acres in the botanical study area. The exact number of individual limber pine occurring within the Rocky Mountain Foothill Limber Pine-Juniper Woodland found within the upper reservoir area was not determined. Limber pine is a dominant species and therefore, according to the 2021 study plan, was mapped as a community. Limber pine in this vegetation community accounted for at least 30 percent of the tree cover in the area of the proposed upper reservoir and was observed as mature and saplings.

Fifty-six occurrences of limber pine were identified in the 2022 study area. These are considered isolated occurrences of limber pines and not part of a vegetation community due to the sporadic distribution and low percent cover observed. Several of these occurrences are documented within a shrub community of rabbitbrush, gooseberry, sagebrush, and bitterbrush. The 56 occurrences are located throughout the study area, with most occurring along the western portion, especially along the two-track road leading to the edge of Seminoe Reservoir. Occurrences range from an individual limber pine to up to 24 trees. In total, approximately 342 limber pine individuals were documented in these isolated occurrences. A map series depicting the limber pine occurrences as well the distribution of Rocky Mountain Foothill Limber Pine-Juniper Woodland in the study area is provided in Appendix E.