Plant and gastropod species richness across fragmented urban landscapes: Patterns and environmental drivers

Abstract

Understanding biota distribution and species richness patterns in fragmented urban environments is crucial for conservation and management.

We surveyed 30 plots in a medium-sized European city to assess vascular plant and terrestrial gastropod species richness in isolated forest patches (IFP), connected forest patches (CFP), and continuous forest (CF), with 10 plots per category. Environmental drivers such as Ellenberg's indicator values, vegetation cover, coarse woody debris, litter, and directly measured microclimatic factors like temperature and humidity were examined.

Significant differences among forest types were found in stand structural characteristics and environmental conditions. IFPs had higher soil pH, more woody debris, and more substantial litter accumulation, with higher temperatures and lower humidity than CF and CFPs, especially in early summer. CF and CFPs mitigated extreme temperatures, leaving IFPs more vulnerable. IFPs had the highest plant species richness, especially neophyte and archaeophyte species, while CF plots had fewer species, mainly of the Carpinion association, indicating more natural conditions. Gastropod species richness and densities were also highest in IFPs. GLMs identified the landscape category as the most significant predictor of species richness for plants and gastropods. Plant species composition varied significantly among forest types, notably for Carpinion and neophytes, whereas gastropod species composition remained consistent.

These findings highlight the complex interplay between environmental factors, urbanisation, and species richness in urban forests. The study underscores the importance of landscape categories, ecological factors, and fragmentation in evaluating species richness patterns in urban and suburban forested areas using plants and gastropods as linked ecological indicators.