Format: ORAL

Diego S. Podadera1,2, Annie Deslauriers2, Sergio Rossi2, Lorena Balducci2

1 Department of Forest Science, Soils and Environment, São Paulo State University-UNESP, Botucatu, Brazil 2 Département des Sciences Fondamentales, Université du Québec à Chicoutimi-UQAC, Chicoutimi, Canada

The emergence of buds marks a critical phase in the life cycle of plants, signifying an essential response to seasonal shifts in weather patterns. Within boreal forests, distinct species display unique phenological behaviors, and their responsiveness to warming conditions can vary significantly. This study focuses on examining the budburst timing across Canada within three coniferous species, Balsam fir (Abies balsamea), black spruce (Picea mariana), and white spruce (Picea glauca) (Pinaceae). Our study encompasses 2839 locations spanning from 1980 to 2021. Our analysis involved identifying the triggers for budburst, assessing its acceleration rate, and discerning the spatiotemporal patterns in relation to climate. We developed response functions between budburst and climate (air temperature, precipitation, and solar radiation), and used the strongest correlations to test their effect on budburst. Employing spatially constrained multivariate clustering techniques, we discerned distinct budburst patterns across Canada territory. Our findings revealed a baseline disparity of 17 days between black spruce and balsam fir/white spruce budburst timings. Additionally, we observed a negative correlation between the mean minimum May temperature and budburst date. Black spruce exhibited a notable advancement in budburst at a rate of -3.33 days C?, twice the rate of balsam fir and white spruce (-1.53 and -1.27 days C?, respectively). Notably, the clustering of budburst timings corresponded closely with Canadas ecoprovince distribution, aligning with temperature gradients across the nation. Mays mean minimum temperature emerged as the primary driver for budburst in northern tree species. Our projections suggest an earlier budburst in a warmer spring, with black spruce displaying the most pronounced rate of change. Intriguingly, the identified clustering patterns remained consistent despite the longitudinal precipitation gradient across Canada. This study underscores the intricate relationship between climate, geography, and the timing of budburst in boreal tree species.