Deciphering the black spruce response to climate variation across eastern Canada using a meta-analysis approach

Abstract

Boreal forests are experiencing climate change more rapidly than other biomes, which is likely to impact their future management. Understanding how tree growth responds to regional and seasonal variation in climate is essential to anticipate future management of boreal forests. We compiled and summarized black spruce climate-growth relationships from 11 dendroclimatology studies in boreal forests of Northeastern North America. Using a statistical synthesis of 113 sites and 2,995 black spruce trees, latitudinal trends were found to affect the growth response to monthly climate variables. Below 50°N, a high portion of sites showed a negative growth response to summer temperatures, whereas these were positive between 50°N and 54°N. Growth response to previous summer precipitation was consistently positive across latitudinal range. This shift from negative to positive growth response to summer temperatures observed between 50 and 51°N was confirmed through meta-analysis and was found to be associated with a mean annual temperature of ∼ 0 °C. This threshold is likely representative of the limit at which black spruce growth shifts from being moisture- to temperature-limited. By directly relating growth-climate relationships to mean annual temperature and precipitation at a given site, our meta-analysis allows readers to easily grasp the current growth response of black spruce to climate variation. Combined with climate projections, our results may also be used to facilitate the estimation of black spruce growth trends through time, and thus inform the implementation of adaptative silvicultural measures.