Projected winter warming unlikely to affect germination success of balsam fir regeneration in Atlantic Canada

Abstract

Abstract Climate warming has the potential to influence forest composition and species recruitment over the course of the 21st century. Although many of these impacts are expected to occur during the growing season, important life history events, like seed dormancy release, may be affected during the winter. For seeds of balsam fir (Abies balsamea (L.) Mill.) to germinate, they require a lengthy cold stratification period to break seed dormancy, which may not be experienced under warmer winters. Moreover, within Atlantic Canada, balsam fir populations experience very different climates. Dissimilarities among the genetics of these balsam fir populations and adaptations to their local environments may engender variations in population response to winter warming. In this study, we selected three balsam fir seedlots each from four different seed origin zones within Atlantic Canada and subjected them to simulated winter warming in outdoor seed plots that were heated to ≈ 6°C above the ambient temperature from December to April. Contrary to our hypotheses, germination success of the heated balsam fir seeds did not significantly decrease relative to the controls, and there was no interaction between warming and seed origin zone. Seedlots of some seed origin zones exhibited variable responses to warming, suggesting that dormancy levels substantially differ among populations from similar climates. This diversity in phenotype expression within balsam fir populations may improve this species resilience under future climate change.