Examining the role of landscape structure and dynamics in alien plant invasion from urban Mediterranean coastal habitats

This paper aims to disentangle the effects of both current landscape structure and recent land use-change on alien plant invasion in urban Mediterranean coastal habitats. Patches of four habitat types (rock outcrops, sand dunes, scrublands and forests) of different sizes and surrounding landscape compositions were selected along the coast of the Metropolitan Region of Barcelona (NE Spain). Attributes of habitat patches, historical (1956) and current landscape composition around them, land-cover changes (1956-2005) and other environmental and geographic factors within these patches were obtained. The association of these attributes with alien plant richness, abundance and composition was investigated using GLM and CCA. Alien species richness was mostly explained by patch size and shape and built-up area proportion from 1956 and 2005 in a 50 m buffer around patches. Alien species abundance was mostly related to patch shape, temperature, rainfall, land-cover changes within patches and cropland cover of 1956 in a 50 m buffer around patches. Alien species composition was primary related to habitat type, temperature, land-cover changes within patches and the composition of the surrounding landscape. Results suggest that landscape factors affect alien species richness and abundance differently, which are indicative of species colonization and spread, respectively. Landscape history positively affects both colonization and spread, with evidence for a colonization credit related with past urban cover, and the association between recent patch dynamics and present aliens spread. Results highlight the importance of including landscape structure and dynamics in the management of plant invasions in coastal Mediterranean habitats, especially in metropolitan regions.