Bud flush phenology and nursery carryover effect of paper birch provenances

Abstract: Paper birch (Betula papyrifera Marsh) is an ecologically valuable species with a broad geographic distribution across the North America. Its diversity, versatility and enduring nature make it an ideal candidate for a selective breeding program in this region. However, an understanding of the genecology of this species is fundamental to deploy it successfully. Ten paper birch provenances were collected from British Columbia (BC, Canada) and northern Idaho (USA) along elevational transects to determine whether observed bud flush phenology was due to genetics and /or environmental variation or their interaction. Seedlings were grown at three different nurseries: University of Idaho (46°44’N), Landing (50°17’N) and Little Forestry (54°00’N) and planted in a randomized single tree interlocking block design in three common gardens at Sandpoint, ID (48°13’N), Skimikin, BC (50°45’N) and Red Rock, BC (53°45’N). Results indicate that variation in the timing of bud flush is a complex interaction among local genetic characteristics and environmental conditions of the growing site. Birch bud flush followed a general geographic trend where provenances at the southern common garden (Sandpoint) required less time (Day of Year, DoY) and fewer growing degree days (GDD) compared to central (Skimikin) and northern (Red Rock) common gardens. Although there were significant differences in the timing of bud flush among provenances along an elevational gradient, none of the regions showed the expected linear elevational cline, trends were inconsistent. Further, birch bud flush was significantly influenced by nursery displacement effects in the initial year of establishment but disappeared within three years. These results provide an opportunity to characterize bud flush phenology of paper birch and would be useful for improving operational paper birch seed transfer programs in BC.