Field survey for three sensitive plant species in the upper Big Creek area, Payette National Forest, Idaho

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In 2015, the Payette National Forest (NF) and Mancuso Botanical Services partnered on a Challenge Cost-share project to conduct a field survey for three plant species of conservation concern in the Elk Summit area, located approximately 13 miles (21 km) north of Yellow Pine on the Krassel Ranger District. Target species included Sacajawea’s bitterroot (Lewisia sacajaweana), bent-flower milkvetch (Astragalus vexilliflexus var. vexilliflexus), and whitebark pine (Pinus albicaulis), all Payette NF sensitive plant species. Planning the field survey focused on Sacajawea’s bitterroot because it was the project’s primary target species. The field survey included searches in the Mt. Eldridge - Dixie Mountain, Wolf Fang Peak, Rattlesnake Peak, and Willson Peak areas. One new occurrence of Sacajawea’s bitterroot was discovered approximately 0.4 mile (0.6 km) southwest of Mt. Eldridge along the main ridge leading southward to Dixie Mountain. This new occurrence consisted of two small patches of Sacajawea’s bitterroot located approximately 165 ft. (50 m) apart. Together, the two patches contained a total approximately 100 Sacajawea’s bitterroot plants. Both patches occupied sparsely vegetated ridgecrest/upper slope openings surrounded by whitebark pine - subalpine fir (Abies lasiocarpa) woodland vegetation. The plants were restricted to inclusions of gravelly granitic substrate in an area otherwise dominated by volcanic or other non-granite geology. Human-related threats or disturbances were absent. Sacajawea’s bitterroot was not found at any of the other survey areas, including numerous locations that had open, often extensive exposures of gray - light pink, gravelly rhyolitic substrate. The survey failed to find any new populations of bent-flower milkvetch, and only a few small patches of marginal potential habitat were seen, all in the vicinity of Wolf Fang Peak. Whitebark pine was found to be common in most areas. Overall, the survey found whitebark pine affected by relatively low incidence of white pine blister rust (Cronartium ribicola), variable mortality related to mountain pine beetle (Dendroctonus ponderosae) infestation, and evidence of seedlings and small saplings suggesting ongoing recruitment in most places.

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Reference Code: U16MAN01IDUS <br>

Full Citation: Mancuso, M. 2016. Field survey for three sensitive plant species in the upper Big Creek area, Payette National Forest, Idaho. Report prepared by Mancuso Botanical Services for the Payette National Forest, McCall, ID. 12 pp. plus appendices. <br>

Location: ELECTRONIC FILE - BOTANY: MULTIPLE SPECIES <br>

Keywords: Sacajawea’s bitterroot, Lewisia sacajaweana, bent-flower milkvetch, Astragalus vexilliflexus var. vexilliflexus, whitebark pine, Pinus albicaulis, Payette National Forest, Idaho <br>