A Starting Point: An Ecosystem of Reference for Habitat Restoration of the Northern Idaho Ground Squirrel, Urocitellus brunneus brunneus

The Northern Idaho Ground Squirrel (NIDGS, Urocitellus brunneus brunneus) is threatened by habitat loss due to fire exclusion in west-central Idaho. Increases in Ponderosa Pine (Pinus ponderosa) density and extent have closed historically open meadows. Management practices for NIDGS recovery include thinning and burning to reduce tree encroachment. Baseline habitat data help create restoration goals and refine present management plans, but no pristine reference sites exist for the NIDGS, due to 100 y of land use and a lack of historical records. Therefore, we provided the first quantitative habitat descriptions of NIDGS habitat at 7 currently occupied sites that may be useful as an ecosystem of reference. We chose habitat attributes that are likely important to NIDGS, as well as attributes that are potentially altered by restoration treatments, which included overstory canopy cover, tree density, ground cover, litter depth, and soil texture. Habitat attributes were described with Bayesian 95% credibility intervals. Sites occupied by NIDGS had tree canopy cover of 10 to 15%, tree densities of 64 to 118 trees/ha, and understory height was 20 to 25 cm. Understory vegetation of occupied habitat consisted of 20 to 30 species, while across-site richness was 153 species. We also identified 15 understory species with the highest constancy and cover across the 7 sites. Litter depth was 0.7 to 0.9 cm, and the soil texture was clay loam. Our study provides valuable baseline information about NIDGS habitat. Managers may use our results to develop appropriate restoration targets when implementing habitat restoration. Information on occupied habitat may increase the efficacy of currently implemented restoration techniques and provide knowledge to be used in an adaptive management framework.