Ecology of whitebark pine populations in relation to white pine blister rust infection in subalpine forests of the Lake Tahoe Basin, USA: Implications for restoration

For over a century, white pine blister rust (WPBR), caused by the introduced fungal pathogen, Cronartium ribicola J.C. Fisch., has affected white pine (Subgenus Strobus) individuals, populations, and associated forest communities in North America. We surveyed eight populations of whitebark pine (Pinus albicaulis Engelm.) across a range of environmental conditions in subalpine forests of the Lake Tahoe Basin, California and Nevada, to determine how WPBR is influencing host fecundity (i.e., female cone production and recruitment), survival, and current population trends. In this region and throughout its range whitebark pine is an important component of subalpine ecosystems. In high-elevation forests of the Lake Tahoe Basin, the primary negative effect of this rust pathogen on whitebark pine is infection and mortality of cone-bearing branches. Mean incidence of WPBR among whitebark pine populations was 35% and ranged from 1% to 65%. Given the high disease incidence, relationships were found between WPBR infection and reproductive output. Percent of individuals infected per population (R 2 = 0.78), average number of WPBR-infected