Influence of Site Conditions, Shelter Objects, and Ectomycorrhizal Inoculation on the Early Survival of Whitebark Pine Seedlings Planted in Waterton Lakes National Park

Whitebark pine (Pinus albicaulis) is an endangered five-needle pine limited to high elevations in western North America. Populations are being decimated by white pine blister rust, mountain pine beetles, and fire suppression. Over 200,000 rust-resistant seedlings have been planted for restoration in the western United States, but survival rates are low. Several treatment combinations (planting on burns, in beargrass, near shelter objects, and with mycorrhizal inoculation) intended to enhance the survival of planted nursery seedlings were evaluated. Each of 21 plots contained four site condition combinations (burned/not, beargrass/not). Half of 983 seedlings were inoculated with the native ectomycorrhizal fungus Suillus sibiricus in the nursery. Seedlings were planted with/without a shelter object (stumps, logs, rocks). After 2 years, some of the highest seedling survival rates (82%) were in burned areas (prescribed torching) where beargrass mats were absent. In unburned areas with beargrass, mycorrhizal treatment increased survival 17-24% and when combined with shelter objects was 68-84%. Shelter objects increased survival 10 -12.5% on burns and 31% on unburned areas without beargrass, where survival was low (42%). Overall, early seedling survival was higher than for other whitebark pine restoration attempts at 95% and 69% for years one and two, likely due to particular treatment combinations possibly helped by favorable spring moisture conditions.