Experimental assessment of the intraspecific variation of climate adaptive capacity in balsam fir seedlings
University of New Brunswick
Increasing frequencies of heat waves and drought are expected to shift the composition and growth of balsam fir (Abies balsamea (L.) Mill.), a widely distributed cold-adapted boreal species. We conducted a climate-controlled greenhouse provenance experiment to assess the climate adaptive capacity of balsam fir seedlings. In the treatment year, we found sizeable growth acclimation to temperature and drought treatments beyond worst-case climate change projections within the species natural range. Acclimation was complimented with high levels of phenotypic plasticity, likely improving seedling resistance to treatment effects. In the following growing season, we subjected all of the treatment groups to a single ambient treatment to assess for lagged treatment effects from the prior year. We found that legacy growth declines were extremely pronounced in the warmest treatment groups, with relative growth rates far lower than in the treatment year. Furthermore, we observed that levels of seedling recovery and resilience were positively correlated with provenance-specific temperatures, indicating considerable adaptive phenotypic diversity. Our study results suggest that balsam fir seedling growth is not limited by the worst-case climate change scenario, instead, heat and drought stress may have a greater influence on later stages of regeneration, or they may reduce seedling competitiveness and resilience through the impact of legacy effects. Regardless, our findings solidify the importance of integrating provenance origin, lagged-growth effects, and ontogeny into future research aiming to predict the responses of plant growth and distribution under a changing climate.