Assessment of assisted migration effects on spring bud flush in white spruce (Picea glauca ) seedlings

In a changing climate, delaying the time of bud flush may be advantageous to boreal forest species to reduce the risk of spring frost damage. In this study, we examined the potential effect of assisted migration of tree seed on time to bud flush for white spruce. Flushing times of seedlings from 23 white spruce provenances from Ontario were observed under varying temperature conditions simulated in controlled environment chambers. Results indicated that time to bud flush varied considerably among provenances. Although higher temperatures significantly promoted bud flushing for all provenances, provenance-by-temperature interactions were negligible, indicating stable performance of white spruce provenances for this adaptive trait. Spatial patterns of variation among provenances in bud flushing were not consistent with patterns found in range-wide provenance tests. Assisted migration of tree seed across relatively short distances is unlikely to delay bud flushing time in white spruce. Some southern populations may flush earlier at more northerly sites, which would exacerbate spring frost risk. Tree improvement may be an effective approach to utilize among- and within provenance variation to enhance this fitness trait for better climatic adaptation.