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Justine Karst

Ph. D. candidate, Department of Botany
University of British Columbia

Academic Background

In 1992, I completed the first two years of my undergraduate degree at the University of Victoria, British Columbia. I completed my B.Sc. with a major in Land Reclamation at the University of Alberta in 1999. From there, I moved to Montréal, Québec to do a M.Sc. in the Biology Department of McGill University with Prof. Martin Lechowicz ( The title of my thesis was “Ecological separation among fern species in an old-growth forest”. I was fortunate to have the opportunity to study the fern flora of Mont Saint Hilaire (, a reserve representing the largest tract of old-growth forest in the St. Lawrence River valley. I am currently in my fourth year of my Ph.D. in the Botany Department at the University of British Columbia studying the role of ectomycorrhiza in determining the ecological breadth of tree species. I am co-supervised by Profs. Melanie Jones and Roy Turkington. I expect to complete my Ph.D. within the next two years.

Research Program

My Ph. D. can essentially be divided into two components. The first component aims to determine the role of ectomycorrhizas in defining the ecological breadth of tree seedlings of two species, lodgepole pine and Douglas-fir. Relying mostly on an experimental approach, I investigate the effects of ectomycorrhizal identity on seedling growth responses. I manipulate ectomycorrhizal identity either by growing seedlings in soil collected from sites that are thought to vary in ectomycorrhizal community composition, or I directly inoculate seedlings with different species of ectomycorrhizal fungi. Within this context, I am testing if the presence of ectomycorrhizas increases the ability of a host to tolerate a broader range of environmental conditions.

The second component of my Ph. D. examines how various ecological factors structure ectomycorrhizal diversity. Ecological factors that I consider are environmental heterogeneity, and interspecific and intraspecific host differences. From previous research, it appears that the ectomycorrhizal community composition found on seedlings is both host and site specific, however less is known on whether intraspecific variation within hosts accounts for differences in ectomycorrhizal communities. Using lodgepole pine seed from controlled pollination trials, I have inoculated each seed family with various ectomycorrhizal species. I expect there may be particular combinations of seed family and ectomycorrhizal fungi that result in relatively higher or lower seedling growth than that of the average seedling. This would then suggest that “fine-tuning” between symbionts occurs below a species level, and is in fact dependent on intraspecific host characteristics.


Weber, A., J. Karst, B. Gilbert and J. Kimmins. 2005. Thuja plicata exclusion in ectomycorrhiza-dominated forests: testing the role of inoculum potential of arbuscular mycorrhizal fungi. Oecologia 143:148-156.

Karst, J.,  B. Gilbert and M.J. Lechowicz. 2005. Fern community assembly: the roles of chance and the environment at local and intermediate scales. Ecology 86:2473-2486.

Last reviewed shim5/8/2013 6:23:33 PM