BA (2002) Swarthmore College, Pennsylvania

Current research:
(1) Will whitebark pine (Pinus albicaulis) move north with climate change? Ground-truthing species distribution models while testing facilitated migration using common gardens (project description)
(2): Genetic trends in lodgepole pine (Pinus contorta) radial growth relative to climate variables (project description)

Aitken, S.N., Yeaman, S., Holliday, J.A., Wang, T., Curtis-McLane, S. 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evolutionary Applications (1): 95-111.

Research summary
The unprecedented rate of climate change that occurred during the twentieth century is projected to continue throughout and beyond the fossil fuel era, provoking concerns regarding how native species are and will continue to respond to new climatic conditions. Specifically, an understanding of how the germination, growth and survival of trees is impacted by climate change is of huge relevance to conservation planners and to the forest industry. Empirical studies regarding how trees respond to temperature and precipitation regimes divergent from those they have historically experienced are particularly useful for predicting how populations may migrate and adapt under future climate change scenarios (Aitken et al. 2008).
Tree ranges will need to move polewards or higher in elevation as global temperatures increase in order to avoid becoming extirpated. Species distribution models are being coupled with global climate models in order to predict future distributions of species based on their current climatic amplitudes. However, species distribution models have the weakness of ignoring the numerous biotic and abiotic factors that interplay with climate to determine migration potential, such as genetics, seed dispersal, geographic barriers and interactions between species (Aitken et al. 2008). While conservation biologists are interested in the accuracy of using such models to map the potential range shifts of threatened taxa under climate change scenarios, the timber industry is concerned with how different populations are expected to respond to climate change so as to optimize species and seed source selection for reforestation and minimize reductions in health and productivity.
The Centre for Forest Conservation Genetics at UBC has created the leading climate model for the province of British Columbia, Climate BC (Wang et al. 2006), and species distribution models for all 50 native tree species (Hamann and Wang 2006). These models generally show a high correspondence between actual species ranges and climatically projected ranges for most of the province's trees; however, some species, particularly those with small ranges such as whitebark pine (Pinus albicaulis) show major discrepancies. Others, such as the critical timber species, lodgepole pine (Pinus contorta ssp. latifolia), have large ranges and a high degree of fit between their current actual and current predicted ranges, but their future habitat as defined by climate is projected to decline dramatically - 50%in area in the case of lodgepole pine.
My projects use common gardens - genetically unique populations planted together in a series of experiments along a diverse biogeoclimatic spectrum - to empirically test and refine current modeling protocols. For the lodgepole pine work, trees from a world-renowned common garden experiment established by the Ministry of Forests and Range in the 1970s were cored and the annual rings measured for use as a proxy for how growth trends of populations may respond to climate change. This information will be used to refine predictions of how growth and yield may change under future climate scenarios, as well as used to recommend alterations in seed transfer guidelines.
Whitebark pine is a blue-listed species that is being threatened within its current range by a host of climate change-related diseases and threats. Large areas in the northwest portion of British Columbia that are projected to become primary refuges for the species under climate change scenarios are hypothetically also potentially habitable under current climate conditions, which begs the question of why whitebark pine doesn't grow in those areas already. My project involves planting whitebark pine common gardens within and outside of the current actual and climatically projected current range of the species, in order to emperically test the species distribution models, as well as to assess the ecological and social ramifications of assisting species migration should the conservation concern get to the point where such intervention is needed. This work will be supplemented with indoor growth chamber experiments that will further test the climatic limits of the populations.

Aitken, Yeaman, Holliday, Wang and Curtis-McLane, 2008. Evolutionary Applications (1): 95-111.

Hamann and Wang. 2006. Ecology (87): 2773-2786.
Wang, Hamann, Spittlehouse and Aitken. 2006. International Journal of Climatology (26): 383-397.

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