Lemhi Penstemon Inventory

Background

Lemhi penstemon (Penstemon lemhiensis) is a short-lived perennial forb that is endemic to Lemhi County in eastern Idaho and 4 counties in southwest Montana, including Beaverhead County where Big Hole National Battlefield (BIHO) is located. The species is known from only 191 occurrences, 102 of which are in Idaho, and 89 are in Montana. Over 50% of these populations are made up of 30 plants or less. There are only three large populations with over 300 plants. One of these occurs in BIHO and it may be the largest known population of the species. Lemhi penstemon is listed as a sensitive species by the US Forest Service and the Bureau of Land Management, and is ranked G3 and S3 (rare but not imperiled with 21-100 occurrences in the state) by the Montana Natural Heritage Program. The species has reportedly been in decline throughout its range, and is facing threats from altered fire regimes and invasion by spotted knapweed. The species requires bare soil microsites to become established and prescribed burning has been demonstrated to be effective in stimulating germination and population growth. Given the large, globally significant population size at BIHO, and the potential declines reported elsewhere in the species' range, documenting the distribution and abundance of Lemhi penstemon at BIHO is important, and will support more informed management decision-making.

Objectives

• Estimate the distribution and abundance (population size) of Lemhi penstemon in BIHO.

Results/Future Plans

Inventory efforts in 2007 recorded 520 mature flowering plants, and the 2009 inventory resulted in a population estimate of 1385 mature plants. The precision of this estimate was low (approximate 95% confidence interval 495-2275 plants) because of the sparse distribution of plants, but the results confirm that the population remains well above 300 plants, and therefore represents a globally significant Lemhi penstemon population.

Future inventory efforts will further expand park management knowledge of the Lemhi penstemon population, including information on population size, impending threats, and potential management options (such as prescribed fire). This knowledge will inform park resource planning and land health reporting.

Contact Information

Tom Rodhouse
Upper Columbia Basin Network Ecologist
National Park Service
2600 NW College Way - Ponderosa Bldg.
Bend, OR 97701
Email

Document Links

• Resource Brief (link to Reports & Pubs page)
• Penstemon Inventory Report (link to Inventory Reports page)