Exploring the distribution pattern of native and alien forests and their woody species diversity in a small Mediterranean city.

AbstractRecent studies have explored the ecological relationship between native urban forests and self-sown non-native forests in large cities and metropolises but further research efforts dedicated to analyzing this relationship in small cities are still needed. To improve our understanding of the ecology of urban native and alien forests in Mediterranean small cities, we analyzed the woody species richness, the community-weight mean of moisture and nitrogen ecological indicators, and soil disturbance indicators in the main urban wood types of the city of Campobasso (Italy), as well as their spatial distribution pattern across a gradient of cover and aggregation of green areas. The study showed that both native oak forests and <italic>Robinia pseudoacacia</italic> forests contributed to the maintenance of woody species richness. If we exclude the riparian environment, <italic>R. pseudoacacia</italic> forests occupied small marginal patches, tolerating soil disturbance and a high disturbance frequency, thus occupying habitats where the native oak forests could not grow. Conversely, <italic>R. pseudoacacia</italic> forests shared the ecological niche with the native riparian forests, which calls for action to prevent the spread of this alien species along river banks. Our results highlighted that urban remnant forests should be considered important assets for the planning and upkeep of urban green areas. [ABSTRACT FROM AUTHOR]