Nitrogen and mycorrhization in Pinus ponderosa and Pinus contorta germinants the first growing season after wildfire or clearcutting

Although ectomycorrhizal associations have been studied in great detail in mature stands, lab settings, and greenhouse studies, very little research has been conducted examining the early stages of the symbiosis in the field. With a changing climate, fire regimes, and harvesting practices, it is imperative we understand how this relationship establishes in a natural setting. By collecting lodgepole and ponderosa pine seedlings during their first growing season in the appropriate biogeoclimatic zones, in areas that were affected by a clearcut or severe wildfire the year before, I was able to identify when signs of colonization on pine roots first began, the rate at which fungi colonized new germinants, and how this related to nutrition and growth. Seedlings collected in this study started to show signs of colonization in July, a month after germination was first observed. There was a mixture of colonized and uncolonized seedlings collected in the summer; lodgepole pine seedlings that were colonized generally had higher nitrogen contents and biomass compared to uncolonized seedlings collected at the same time. This suggests that the fungi were aiding in nutrient acquisition, even within the first weeks after mycorrhiza formation. By the end of the season, all collected seedlings had ectomycorrhizae present on their roots, so fungal inoculum did not appear to be limiting on severely burned or recently clearcut sites. The genera of fungal species present on the plant root tips did not seem to have an effect on the amount of seedling N, or biomass.Science, Irving K. Barber Faculty of (Okanagan)Biology, Department of (Okanagan)Graduat