Annual aboveground carbon uptake enhancements from assisted gene flow in boreal black spruce forests are not long-lasting

Abstract

Assisted gene flow between populations has been proposed as an adaptive forest management strategy that could contribute to the sequestration of carbon. Here we provide an assessment of the mitigation potential of assisted gene flow in 46 populations of the widespread boreal conifer Picea mariana, grown in two 42-year-old common garden experiments and established in contrasting Canadian boreal regions. We use a dendroecological approach taking into account phylogeographic structure to retrospectively analyse population phenotypic variability in annual aboveground net primary productivity (NPP). We compare population NPP phenotypes to detect signals of adaptive variation and/or the presence of phenotypic clines across tree lifespans, and assess genotype‐by‐environment interactions by evaluating climate and NPP relationships. Our results show a positive effect of assisted gene flow for a period of approximately 15 years following planting, after which there was little to no effect. Although not long lasting, well-informed assisted gene flow could accelerate the transition from carbon source to carbon sink after disturbance.

Abstract

The long-term effectiveness of assisted gene flow of trees could be jeopardised by rapid climate change. Here the authors analyse a large dataset of relocated black spruce populations in Canada, finding that local adaptation to climate of origin improved NPP responses, but only for up to ~15 years after planting.