Considering Urban Social Functions at Fine Spatial Resolution to Understand the Distribution of Invasive Plant Species in Cities

Abstract ContextCities are high sources of plant invasions. To understand mechanisms of introduction and dispersion of invasive alien species (IAS) in city, we need a thoroughly description of the social and structural components of urban landscapes. ObjectivesWe assessed the effects of neighborhood types and their associated human activities and structural linear elements on the distributions of IAS in a French medium city (Blois). We examined how the relative contributions of these variables varied between scales of analysis. MethodsWe recorded the presence of seven IAS species in the entire city (22 km²), at three spatial resolutions: 100×100m, 200×200m and 400×400m. We characterized neighborhoods through their main covers, human uses, and ages and structural elements through impervious soil, area of and distance to roads and railways.ResultsNeighborhood type was the most important variable in explaining IAS distributions. This variable was especially important at the finest scale which allowed a fine urban classification. B. davidii and B. aquifolium were found in individual residential neighborhoods, whereas R. pseudoacacia and A. altissima were most encountered in industrial areas. The effects of the structural elements differed between species and were lower. ConclusionsCharacterizing the high spatial and functional heterogeneity of urban landscapes at fine scale is critical to understand IAS distribution patterns. We show that considering human uses and planting practices is determinant to understand IAS introduction patterns. Then, linear transport corridors and ruderal conditions explain the dispersion and establishment of IAS across the city and potentially to the surrounding natural spaces.