Liana distribution in response to urbanization in temperate forests

Urbanization results in ecosystem fragmentation, habitat loss, and altered environmental conditions that usually favour pioneer and ruderal species. The objective of this study was to evaluate the impact of urban conditions on liana abundance in temperate forests. Fieldwork was conducted in 50 forests of the metropolitan Montreal area (Quebec, Canada) and focused on the 6 most common lianas of the study area, Celastrus scandens, Menispermum canadense, Parthenocissus quinquefolia, Solanum dulcamara, Toxicodendron radicans, and Vitis riparia. Potential drivers of liana distribution at the landscape scale (e.g., surrounding land use, urban heat island) were quantified based on satellite images and land use maps. At the forest scale, we investigated biotic and abiotic variables in 429 sampling plots. We found that at the landscape scale, lianas benefited from urbanization, mainly through warm microclimates created by urban heat islands (UHI) as lianas are not well adapted to cold climates. At the forest scale, lianas were more abundant in disturbed forests and in edge habitats than in less disturbed forest and core habitats. Their fast growth rate enables them to quickly take advantage of high light availability on disturbed sites. Our results suggest that urbanization and ongoing climate changes will lead to an increase in liana abundance in temperate forests.