Application Of A U-W Method For The Detection Of Boreal Forest Response To Environmental Changes In Canada

To better understand the long-term response of boreal forests to increasing environmental changes, we applied the u-w method to detect growth changes triggered by environmental factors. Three species (Picea mariana, Picea glauca, and Populus tremuloides) of various sizes and ages were sampled in a boreal forest in northern Canada. Several stem disks were collected from the base to the crown of seven or eight trees in each of ten plots and ring width was measured to estimate the annual volume growth of each tree. Growth shifts, or changes in the phase of volume growth, were observed in every tree, and some shift years were common to the plots and species, suggesting the same environmental impact on trees. More frequent growth shifts were observed in the smallest trees in the black spruce plots, but showed no common patterns among the trees of different ages/sizes and species. Common growth shifts across species and plots were observed after severe drought years associated with fire incidences. We concluded that the u-w method is useful for detecting multi-year climate impacts on tree growth.