Urban tree resiliency to heat and drought stress across Canadian cities
Urban trees are expected to help in mitigating the negative effects of climate change on infrastructures and human well-being in cities but warming climate with longer and more intensive dry and hot periods will also affect urban tree function and survival. To better understand the resilience and resistance of urban trees in the face of climate change, we conducted a Canada-wide collection of tree cores from cities with diverging climates (Edmonton, Montreal, Quebec City, and Halifax).
We use dendrochronology to assess tree growth responses to dry and hot periods, comparing common urban tree species with differing water-use strategies in parks and on streets. We expected street trees to show more growth reductions than park trees after dry and hot periods due to the more restrictive conditions. Preliminary results in Montreal show that contrary to our initial hypothesis, street trees seem to be more resilient to thermal and drought stress and present more variability in growth in comparison to park trees among honey locust, green ash, and Siberian elm. Street tree species comparisons in Edmonton revealed that green ash trees were more susceptible to years with low precipitation, while bur oak were more impacted by years with high temperatures. However, in all cases, there appears to be recovery in growth following the notable years.
We will also examine tree growth responses over the climate gradient to see whether heat waves and dry periods affect tree growth more negatively in cities with hot summers in comparison to cities with cool summers. With this information, we aim to form predictions on the growth and resilience of urban trees in the future conditions.