Plant species diversity and vegetation in urban grasslands depending on disturbance levels

Over the last few decades, maintaining biodiversity and ecosystem functions in urban areas has become a challenge. In this study, I investigated the grassland vegetation of three urban habitat types, namely, peri-urban areas, urban roadsides and vacant lots in the city of Izmir (Western Turkey). I used 50 sampling plots for each habitat type resulting in 150 plots in total for the analysis. I tested (1) whether different disturbance levels affect species richness/diversity and composition along urban-rural gradient, and (2) whether biotic homogenisation strongly occurs in disturbed habitats. I found that the species richness/diversity and composition were strongly affected by different disturbance levels in urban areas. Urban roadsides (which were in intermediate position along the urban-rural gradient) showed the lowest species richness, Shannon and Simpson diversity, while vacant lots and peri-urban grasslands had higher species richness and diversity. These results contradict the urban-rural gradient hypothesis which predicted the lowest species richness at the urban end of the gradient. Few alien species were found with only slightly increasing abundances due to disturbances. Considerable biotic homogenisation did not occur. The study system was probably relatively resistant to disturbances. The Mediterranean climate and long history of human influence in the study area have been a reason for such resistance. Urban grasslands play important role in urban biodiversity and ecosystem functioning, therefore they are important for human well-being.