PARENT SESSION
Poster Session 37: Forest Ecology.

Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

Evaluating natural selection as a management strategy for restoring whitebark pine.

McKinney, Shawn^*,1, Tomback, Diana², ¹ University of Montana, Missoula, MT² University of Colorado-Denver, Denver, CO

ABSTRACT- Whitebark pine (Pinus albicaulis), a keystone species of subalpine forests in northwestern United States and southwestern Canada, is in danger of regional extinction. Mortality from an introduced fungal disease, white pine blister rust (Cronartium ribicola), and successional replacement by shade-tolerant competitors following decades of fire suppression, have drastically reduced whitebark pine basal area and opportunities for regeneration. This study examined the likely effectiveness of the natural selection stand approach to whitebark pine restoration. This management strategy is based on Clark's nutcrackers (Nucifraga columbiana) dispersing seeds from rust-resistant trees located in heavily damaged stands and caching them in forest openings created by restoration burning or thinning. The model predicts that genetic resistance in dispersed seeds coupled with an absence of competing species will, in 50 years, lead to stands dominated by rust-resistant whitebark pine. To determine whether increased rust damage influences seed dispersal potential and the likelihood of restoration through natural regeneration we measured structural and compositional characteristics of five one-hectare stands in Montana and Idaho and observed cone survival of 183 whitebark pine trees (2,436 cones) found in the stands. Comparable stands varied in degree of blister rust damage but otherwise did not differ considerably in structure and composition. Slopes of the regression lines of cone survival for the five stands differed significantly. Stands with higher levels of rust damage had significantly lower cone densities, cone survival, and probabilities of seed dispersal than ecologically similar stands with lower rust damage. Results demonstrate that increasing blister rust levels reduce seed dispersal potential at the stand level. To increase chances of dispersal into prepared sites, restoration projects should be chosen based on cone density and spatial configuration of the proximate seed source stand.

Key words: white pine blister rust, dispersal potential, whitebark pine, restoration