Ash Tree Regeneration & Decline in Lake Simcoe Watershed

Abstract

The invasive emerald ash borer (Agrilus planipennis) is currently a major threat to ash trees throughout southern Ontario. We examined 20 plots in the Lake Simcoe Watershed in the years 2017 and 2023 to determine the effect that EAB had on the regeneration of the three major ash species in the region: white (Fraxinus americana), black (Fraxinus nigra), and red ash (Fraxinus pennsylvanica). Analysis was conducted to determine if there were declines in any of the canopy, sub-canopy, shrub layer, ground layer, and basal area of ash trees over the period of six years. Significant decreases were found in both the canopy and basal area but not in the sub-canopy, shrub layer, or ground layer. EAB was found to be having a significant negative effect on only the most mature trees. However, the lower levels were found to have remained the same, indicating that seed production from the top layer has not been significantly hindered by EAB infestation.