Subalpine fir response to drought in northern British Columbia, Canada

Abstract As global warming continues, drought severity and duration are expected to increase in many areas of the world, necessitating a thorough understanding of how trees react to severe drought periods. In this study, we used dendrochronological analyses to determine the response of subalpine fir [Abies lasiocarpa (Hook.) Nutt.] to historical drought events on sites along a latitudinal interval of 500 km in the Rocky Mountains in northern British Columbia, Canada. We used the ClimateBC Climate Moisture Deficit index to approximate drought conditions at the sites and to identify common drought years across sites. We then compared wood densities across the time series to temperature, precipitation, and climate moisture indices for the locations studied to determine relationships between subalpine fir wood densities and climate in this region. We demonstrated that subalpine fir wood density was often negatively correlated to spring and summer temperatures and that these stands are responsive to drought events in the short term. We found that the latitudinal difference between stands was not as pronounced as expected; however, northern sites had a stronger climate response and more frequent drought years than southern sites. This cautiously suggests that the impacts of climate change may be more intensely felt in forests at more northern latitudes. If droughts continue to become more frequent in northern British Columbia, as is predicted with changing climates, we might expect less carbon sequestration and lower wood strength in subalpine fir trees from this region.