Peri-urban Mediterranean plant communities are shaped by chronic anthropogenic disturbances

Abstract

Peri-urban plant communities perform key ecological functions. However, the integrity of peri-urban vegetation is threatened by the continuous expansion of built-up areas and anthropogenic activities, which result in low-intensity, but continuous and pervasive chronic anthropogenic disturbances (CADs). Despite the growing attention to the ecological role of peri-urban vegetation patches, the assessment of the relationship between CADs and typical Mediterranean plant communities at the local scale is still lacking. In this work, both the compositional and functional responses to typical CADs of five vegetation types were assessed in 48 plots, located around the city of Genoa (Italy). The main anthropogenic and environmental drivers of species composition were identified through a Non-Metric Multidimensional Scaling, and selected variables were used to fit a partial Redundancy Analysis. Differences in the number of alien species in relation to total CAD intensity were assessed with a Kruskal-Wallis test. Regarding functional composition, the community weighted mean values (CWMs) of five functional traits were computed for each plot. Generalized linear models were then fitted to assess the relationship between the CWMs and CADs intensity. Our results showed that the specific composition of peri-urban plant communities of Genoa is shaped by interacting environmental and anthropogenic factors. Considering composition, CADs promote the increase of alien species’ number. Moreover, the increased intensity of CADs altered the functional composition, with increasing specific leaf area, leaf nitrogen content and seed bank longevity. Overall, the effect of typical Mediterranean CADs is more pronounced on the functional composition than on the taxonomic composition of peri-urban plant communities. This work highlights the relevance at the local scale of the typical CADs of the Mediterranean area in influencing the different vegetation types that characterise a peri-urban zone.