Increases in the emission of greenhouse gases, particularly during the second half of the 20th century, have been associated with climate warming at the global scale. High latitude areas have been reported to be particularly sensitive to such changes, with significant impacts on plant phenology. The objectives of the present study were to (i) estimate changes in the flowering dates of 18 spring-flowering herbaceous plant species typical of the deciduous forests of eastern North America in three areas of eastern Canada (Gatineau–Ottawa, Montréal, and Québec) from 1900 to 2000 and (ii) associate these changes with those of annual and spring local temperatures. My results show a 2–6 days advance in flowering date over 100 years, depending on the region considered (corresponding to a ~2–3 days advance per 1 °C); these values are somewhat lower than those published in other studies, but still support the increasing body of literature on the effects of climate warming on plant phenology. Shifts in flowering phenology were particularly evident for Montréal, a large metropolitan region; this suggests that global climate warming, and its effects on plant phenology, may be exacerbated by local conditions, particularly those associated with large urban areas. Furthermore, species-specific responses to climate warming, as those presented here, might lead to significant changes in community composition and ecosystem functions.
The phenobs initiative – A standardised protocol for monitoring phenological responses to climate change using herbaceous plant species in botanical gardens