PS 43-80 - Improving ecological functions of urban vegetation islands

Background/Question/Methods

Quebec City is adopting the strategy of increasing green spaces to adapt to global warming, particularly to counteract heat islands, increase biodiversity and canopy cover in older neighborhoods (project of Lab de rue). There is also potential to increase carbon sequestration in soils and vegetation associated with these green spaces. We developed a project (ILOV) with the Ville de Québec to improve ecological benefits and the durability of new vegetation islands. We first evaluated the state of recently established spaces in terms of plant development and cover, diversity of plants, soil quality and microclimate effects. In the first year of the project we reported on the results of our evaluation, and we made recommendations for new urban green islands that will be established in 2022 and 2023 in the older neighborhoods of the city, where green space is lacking.

Results/Conclusions

Our first recommendations from evaluation of recent islands show that maintenance is variable. Some islands are performing certain functions very well, vegetation cover is excellent and plants develop well to cover the soil quickly at the beginning of the growing season. Other islands have not been well maintained and their utility can be brought into question. We make recommendations to return and improve these latter spaces by potentially adding protective barriers, adding more resistant plants, or changing the configuration of the space. The soil substrates used are generally coarse-textured, which has implications for the conservation of fertility in the long term, and therefore plant durability.

For the new vegetation islands to be installed in the next two years, we are proposing diverse mixtures of mainly indigenous plants, more vertical complexity in plant forms, and nitrogen fixing species either as trees, shrubs or perennials. We demonstrate some of the models that have been proposed to the city. Social questions of acceptability will also be explored in response to the new green spaces in these neighborhoods.