Mycorrhization, physiognomy, and first-year survivability of conifer seedlings following natural fire in Grand Teton National Park

Abstract

Ectomycorrhiza formation, survivability, and physiognomic characteristics were assessed for conifer seedlings encountered 1 and 2 years postfire in the Huck burn site near Grand Teton National Park. Pinus contorta Dougl. ex Loud. germinated and was abundant throughout the first growing season. Abies lasiocarpa (Hook.) Nutt. germinated during May and June but was rarely encountered by September. First-year survivorship of P. contorta seedlings was about 50% for east-facing burn and edge and west-facing burn treatments. Mortality was higher in the west-facing edge treatment at about 64%. Pinus contorta seedlings collected in July and August had allocated approximately 75% more biomass to epicotyl production than to hypocotyl production, whereas by September seedlings had allocated 30-50% of their biomass to hypocotyls, regardless of site or treatment. Few or no ectomycorrhizae were formed until September. By September 100% of surviving seedlings were ectomycorrhizal. The number of ectomycorrhizae was positively correlated with the number of primary needles and the root/shoot ratio. These results highlight the importance of mycorrhizae to conifer seedling survival during the initial growing season and point to alteration of carbon allocation as a primary mechanism affecting seedling survival.