Drivers of plant species diversity in suburban forests: A case study from the Czech Republic

• Urban forests were species-poorer than outside urban areas. • Artificial surfaces promoted spread of non-native species. • Sufficient forest area was needed to maintain forest specialists. • Threatened species survived within agricultural areas. • Forest management was important apart from urban land use. Urbanization, together with land use changes, significantly transforms surrounding habitats, affecting the occurrence of plant species and the diversity of communities they form. However, detailed information on the individual environmental drivers influencing plant species composition of suburban forests remains limited. In this study, we ask: What are the main drivers of plant species diversity in suburban forests? In the city of Brno, Czech Republic, and its surroundings, we surveyed 110 vegetation plots of acidophilous oak and hornbeam forests. Using generalized linear models and canonical correspondence analysis, we studied the effects of urban environmental drivers on various plant species characteristics. Urbanization was the most significant driver since artificial surfaces near forests decreased total species richness and increased both the disturbance severity and the proportion of non-native species. Larger forest areas supported the presence of forest specialists and limited the spread of competitive generalists. Open forest stands surrounded by agricultural areas promoted the persistence of threatened species. Despite the prevailing acidic bedrock, variation in soil pH – common in urban areas – also influenced plant species diversity. In addition, forest management significantly affected vegetation composition, independently of the surrounding land use. Based on our findings, ensuring sufficient forest area, minimizing disturbance, maintaining habitat continuity, and enhancing landscape connectivity are essential for conservation of near-natural forests in urban planning. Management of oak and hornbeam forests should aim to create more open stands, support understorey regeneration, and prevent environmental degradation to sustain their required ecosystem functions.