2016 field survey for Sacajawea’s bitterroot (Lewisia sacajaweana) in the Sawtooth Mountains, Idaho

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Sacajawea’s bitterroot (Lewisia sacajaweana) is a small, ground-hugging perennial herb endemic to the mountains of central Idaho. It is a Forest Service Sensitive species and has a NatureServe conservation rank of G2/S2, indicating imperilment due to rarity or because other factors demonstrably make the species at high risk of extinction. Several areas with known or suspected habitat for Sacajawea’s bitterroot have received only a limited amount of targeted survey work in the past. One of these areas is the Sawtooth Mountain Range near Stanley, Idaho. In 2016, the Idaho Natural Heritage Program, U.S. Fish and Wildlife Service, and Mancuso Botanical Services collaborated on a project to survey for Sacajawea’s bitterroot in the Sawtooth Mountains. The Sawtooths were purposefully targeted because much of the range is designated as the Sawtooth Wilderness Area and/or the Sawtooth National Recreation Area (Sawtooth NRA). These special management designations confer added protection from most human-related disturbance activities. <br>

The field survey discovered new Sacajawea’s bitterroot occurrences in nine of 12 search areas. The survey also relocated one previously documented occurrence, but failed to relocate a second old occurrence having vague location information. All 10 occurrences found during the 2016 survey are located within the Sawtooth NRA, with eight of them also in the Sawtooth Wilderness Area. Most new occurrences had <100 Sacajawea’s bitterroot plants limited to one or a few small patches ≤810m2 (0.2 ac) in size. An exception was the large Observation Peak-Elk Creek Divide occurrence that accounted for approximately 90% of the area and 70% of the Sacajawea’s bitterroot plants documented in 2016. Overall, the field survey tallied approximately 3100 Sacajawea’s bitterroot plants extending over 4.2 ha (10.4 ac). Sacajawea’s bitterroot tended to be distributed as scattered, small, low-density patches at all occurrences. Some occurrences consisted of multiple subpopulations, each representing a single patch of Sacajawea’s bitterroot, or multiple patches located in close proximity to each other. Occurrences discovered in 2016 occupied habitat similar to conditions reported elsewhere for Sacajawea’s bitterroot. <br>

The 2016 survey was biased towards areas near and accessible by trail. Popular hiking/backpacking trails occurred close to the Baron Divide and Southwest of Edith Lake occurrences. Trails passed adjacent to the Cramer Divide occurrence and bisected the Imogene Pass occurrence and one of the subpopulations comprising the Observation Peak-Elk Creek Divide occurrence. Trail use did not seem to be adversely affecting Sacajawea’s bitterroot or its immediate habitat to any noticeable degree at these occurrences, but they all appeared vulnerable to random, recreation use-related disturbances such as trail-cutting or other activities accelerating erosion. In addition, trail maintenance could impact Sacajawea’s bitterroot occurrences located adjacent to a trail if crews were unaware of the plant’s presence. All other occurrences found in 2016 were located far enough away from any trail to limit or eliminate recreation-related disturbances. An exception may be flat, bench-like habitat sites at the Finger of Fate occurrence that looked suitable for campsites. <br>

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Reference Code: U18MAN01IDUS <br>

Full Citation: Mancuso, Michael. 2017. 2016 field survey for Sacajawea’s bitterroot (Lewisia sacajaweana) in the Sawtooth Mountains, Idaho. Report prepared by Mancuso Botanical Services for Idaho Natural Heritage Program, Boise, Idaho and U.S. Fish and Wildlife Service, Idaho Fish and Wildlife Office, Boise, Idaho. 12 pp plus appendices <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: {Lewisia sacajaweana} <br>

Keywords: Sacajawea’s bitterroot, Lewisia sacajaweana, Sawtooth Mountains, Idaho <br>