S07 - Session P2 - Diversification of urban lawns to attract pollinators and to maintain their resilience

Authors: Anaïs Grenier *, Guillaume Grégoire, Valérie Fournier, Frédéric McCune, Colin Favret, Étienne Normandin-Leclerc

Lawns are ubiquitous in North American urban environments and constitute a simplified ecosystem with low plant biodiversity. Considering their spatial importance, these areas have a great potential for improving biodiversity, for example by increasing their attractiveness for pollinators. However, scientific data on the use of alternative ground covers in established lawns is scarce. Thus, the goal of this 2-year project is to monitor the attraction for pollinators and the resilience of four different groundcover species ( Fragaria virginiana Miller , Bellis perennis Linnaeus , Trifolium repens Linnaeus and Thymus serpyllum Linnaeus) incorporated into existing lawns in Quebec City and Montreal (Canada). A total of 11 experimental sites were established in June 2021 using a completely randomized block design with four replicates of six treatments on each site. A conventional mowed lawn as well as an unmowed lawn were also included as controls on each site. Data on plant survival, growth and flowering period was collected at 21-days intervals. In order to evaluate pollinator diversity and abundance, sweep net sampling was performed every three weeks over each plot. A drought occurring in August 2021 resulted in a high mortality rate of the four plant species on some experimental sites, particularly in Montreal. Initial results show that B. perennis consistently produced the largest number of flowers during the season. However, this species was also the most affected by drought and had the lowest survival rate of all groundcovers. All groundcover species were able to tolerate frequent (i.e. every 21-day) mowing. Results from this project will be helpful for homeowners, municipalities and sod growers wanting to improve lawn biodiversity and provide new food sources to pollinators.