Simulated winter warming has negligible effects on germination success of Acadian Forest tree species

Dormant seeds that require long periods of cold stratification to become germinable may be most sensitive to increases in winter temperatures caused by anthropogenic climate change. In this study, we used outdoor plots with infrared heaters to simulate the effects of projected winter warming (+6 degrees C) for Canada's Acadian Forest Region and compared seed germination success of tree species with varying stratification requirements. We evaluated four seedlots each of balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), white pine (Pinus strobus L.), red maple (Acer rubrum L.), sugar maple (Acer saccharum Marshall), and yellow birch (Betula alleghaniensis Britton). Three central findings emerged from this study: (i) none of the tested species were significantly affected by warming; (ii) the random effect of seedlot explained more variation in germination success of deciduous species than it did for conifers; and (iii) balsam fir seedlots exhibited considerable differences in their response to warming, implying intraspecific variation in depth of dormancy. These results suggest seed germination success of the tested tree species may not be impeded by their individual seed characteristics under the magnitude of winter warming projected over the coming century in our study area.