Plant and gastropod diversity across fragmented urban landscapes: patterns and environmental drivers

Abstract Context. Understanding biota distribution patterns and diversity within fragmented urban environments is essential for effective conservation and management. Objectives. The objective is to explore the impacts of fragmentation on plant and mollusc communities by examining their diversity and community composition in isolated urban forests and continuous forest stands along urban-rural gradients. The study aimed to explore plant and mollusc diversity variation across the urban-rural gradient in various landscape categories such as forest islands, peninsulas, and contiguous (control) stands and determine the responsible environmental drivers. Methods. The study surveyed 30 plots in Bratislava City, Slovakia, to evaluate the species richness and density of vascular plants and terrestrial gastropods in different landscape categories (see above); we also utilised microclimate data from selected plots. Results. The islands exhibited the highest number of non-native gastropod and plant species, whereas the control plots showed the lowest. Additionally, the forest islands were identified by an increased soil pH, coarse woody debris and litter content, enhancing the species richness of plants and molluscs. GLMs demonstrate that the landscape category had the most notable impact on the diversity of plants and molluscs. While fragmentation characteristics had an impact on the composition of plant species, they did not have a significant effect on the composition of molluscan communities. Conclusions. The research underlines the significance of landscape categories, environmental factors, and fragmentation characteristics when assessing biodiversity in urban forests. This finding can be used to formulate effective strategies for protecting native biota in fragmented urban forests.