The use of native ectomycorrhizal fungi in the restoration of whitebark pine

Abstract

Whitebark pine (Pinus albicaulis) is an endangered keystone species in western North America. Populations are being decimated by white pine blister rust, mountain pine beetles and fire suppression. Large restoration efforts that include the planting of 200,000 rust-resistant seedlings are ongoing, but survival rates are low. Conifers are routinely inoculated with ectomycorrhizal fungi in the greenhouse to enhance out-planting success, but this has not been tried with whitebark pine. The goal of this project is to examine the use of native ectomycorrhizal fungi in restoration of whitebark pine with a greenhouse and field study. A main goal of the greenhouse study was to determine if low nitrogen fertilizer is conducive to ectomycorrhizal colonization by the native fungus, Suillus sibiricus. The effects of dried/fresh inoculum, short or long containers, and the drip/injection method were also tested. Results showed that mycorrhizal colonization was maintained with a low nitrogen fertilizer (4-25-15 NPK), although colonization declined at higher levels. Long containers were more conducive to mycorrhizal colonization, but differences were minimal for other variables. The field study conducted at Summit Lake in Waterton Lakes National Park is part of an effort to combat seriously declining pine populations. One thousand seedlings, half inoculated with Suillus sibiricus, were planted in clusters of three in four site condition combinations: burned/unburned areas, with and without beargrass. Survival was higher than for other studies one (95%) and two years (69%) after planting (2010). Results could be due to favorable spring conditions, conducive site conditions (terra-torching), and mycorrhizal inoculation on certain sites. Survival was 24% higher on burns in comparison to unburned sites; microsite increased survival across all sites. Effects of mycorrhizal inoculation were site dependent and survival was increased 17-23% on unburned sites with beargrass; inoculation did not impact seedling survival on burns. Survival was lowest (38%) on poor planting sites (unburned, no beargrass) but these sites benefited greatly from microsite presence. Data suggest site conditions strongly influence early seedling survival and that mycorrhizal inoculation may be beneficial when soil fungi are restricted. Longer term monitoring is necessary to determine how variables affect seedling survival in the future.