Landscape Trends (1753–1993) of Whitebark Pine (Pinus albicaulis) Forests in the West Big Hole Range of Idaho/Montana, U.S.A.

Abstract

Pinus albicaulis (whitebark pine) is an important tree species in subalpine forests of the Northern Rocky Mountains. Populations have been declining at unprecedented rates due to the introduction of an exotic pathogen and fire suppression. We initiated this study to evaluate historical trends in Pinus albicaulis abundance along with associated subalpine conifers within a small biogeographically disjunct mountain range. The central objective was to estimate historic trends in subalpine forest composition and structure at the species and community scales. Reconstruction of forest stands reveals an 85% increase in tree volume among all species since the 1870s. Pinus albicaulis has historically dominated most stands associated with Abies bifolia (subalpine fir) and Picea engelmannii (Engelmann spruce) but dominance has shifted to these late-seral species for most of the study area since the early 1900s. We estimate, that since 1753, nearly 50% of the study area has shifted to later successional stages while only 3% has receded to earlier stages. We discuss the implications for Pinus albicaulis and suggest that careful reintroduction of fire can aid in the maintenance of ecological integrity at the community and landscape scales.