Spring bud phenology of 18 Betula papyrifera populations in British Columbia

Abstract

Paper birch (Betula papyrifera Marsh.) is an ecologically valuable and suitable new reforestation species in British Columbia (BC). An understanding of birch's genecology is important to deploy it successfully. Eighteen paper birch populations (49–55°N) were collected from five distinct geographic regions in BC to determine whether observed variability in spring bud phenology was due to genetics, the growing environment or their interaction. Seedlings were grown at three common gardens in Prince George (53°45′N), Salmon Arm (50°47′N) and Victoria (48°29′N) to observe the bud break. Further a controlled photoperiod, a root zone temperature and a translocation experiment from the northern to central garden were conducted to investigate the effect of photoperiod and root temperature on birch bud break. Results revealed that timing of spring bud phenology in paper birch is under genetic and environmental control, following climatic clines based on latitude from south to north. Bud flush at the southern common garden was on an average 25 days earlier and required 177 more growing degree day than the northern common garden. Conversely, our controlled experiments and seed source translocation experiment showed that the signal for the onset of spring bud flush is controlled by air temperature, soil temperature, and photoperiod. These results allow us to characterize spring budburst phenology of paper birch and begin to consider seed zones and seed zone transfer guidelines for BC.