Whitebark pine (Pinus albicaulis) is declining severely and is projected to lose much of its current climatic range by 2080 due to climate change. This study will provide technical insight for decision makers concerned with facilitated migration by evaluating the biotic and abiotic limiting factors associated with recruitment of whitebark pine populations in areas north of the current species range that are predicted to be habitable under future climate scenarios.  

In situ common gardens were established throughout western British Columbia (50.1° to 59.7° latitude) using seeds from 7 whitebark pine populations (44.3° to 54.9° latitude) each represented by 10 open pollinated families. Nine thousand untreated seeds were planted in September 2008 while 7,000 seeds were x-rayed, stratified and clipped to maximize germination potential and then planted in June 2008. Both seed cohorts were assessed for germination relative to genetics, seed treatment, microsite (soil, vegetation, local landscape features), location and climate in August 2008.

Ex situ temperature and drought experiments were performed to focus on climate variables that influence genetically-mediated germination and survival-related quantitative traits in whitebark pine. A total of 3,135 treated seeds from the same seven populations were planted in five growth chambers representing May through September conditions under current and future climate scenarios. The chambers were programmed along a continuum from temperatures that whitebark pines experience within their current species range to 10ºC warmer, representing extreme climate model predictions.  

Results/Conclusions

While germination in the in situ common gardens varied significantly by seed treatment and population, it was not strongly affected by geographic location or microsite during the first growing season. Germination was strongly correlated with seed weight and with snow pack persistence at population origins, and weakly correlated with mean summer precipitation at the planting site. The untreated seeds are expected to continue germinating in the summer of 2009, while the year 2008 germinants should experience climatically influenced growth and mortality.

In the first growing season all quantitative traits (percent emergence of seeds planted, percent emergence of total seeds, days to emergence, height, days to flush, days to second flush and days to final budset) in the ex situ growth chambers varied significantly among temperature regimes, while only percent emergence, days to emergence and height varied significantly among populations as well as chambers.