Valerie Russell
Forests in British Columbia are showing signs of stress due to climate change. Lodgepole pine is the most replanted species in British Columbia (BC), with seed orchards providing nearly half of the lodgepole pine seed used in reforestation. Selection for increased growth has been ongoing for several decades, but early work gave no consideration to how mature trees from improved seeds will survive the changing climate. Climate-based seed transfer matches seeds to future plantation climates, but finding optimal matches requires time-consuming provenance trials. To investigate whether trees grown from improved seed will be able to thrive until harvest (silviculture) or beyond (restoration), a study was completed on 1,200 natural and 976 select 3-year-old seedlings from 125 seedlots within 12 breeding zones (BZs). They were grown in raised beds at UBC (outside their natural range) from 2012 to 2014 to compare how populations of natural and select seedlings vary with their climate of origin. Seedlings were also genotyped, and single nucleotide polymorphisms (SNPs) were statistically associated with phenology, cold injury, and height growth traits. Increased frequencies of positive effect alleles (PEAs) were associated with increased growth, later growth initiation and cessation, and cold injury. PEA frequencies were higher in selected than natural populations, and differences in PEA frequencies were greater between natural and selected seedling populations from warmer localities. Seedlings from the same seedlots were also planted as a validation trial at Alex Fraser Research Forest (within their natural range and approximately 335 kms NNW of UBC). Height measurements of these 10-year-old (2021) saplings were compared to heights and PEA frequencies of the raised bed seedlings at UBC. Seedling results for both phenotypes and PEAs predicted provenance differences expressed by the saplings for both natural and select seedlots with great consistency. The lack of genotype-by-environment interaction between the coastal seedling environment and the continental environment of the field sapling trial was surprising. Using seedling rather than provenance trials, and combining genomics with breeding and selection to characterize provenance differences can decrease the time needed to characterize climate adaptation of natural and select populations for replanting the forests of BC.