Changes in plant diversity along an urban–rural gradient in an expanding city in Kazakhstan, Western Siberia

Abstract

Plant communities respond sensitively to urban expansion and therefore serve as indicators for human land use. An urban–rural gradient approach was used to examine changes in plant species composition and abundance related to human-altered habitats in the Western Siberian city of Pavlodar (Kazakhstan). This region is characterized by harsh continental environmental conditions and recent anthropogenic degradation of the original steppe grasslands as a result of enforced land-use changes (Virgin Land Campaign) and rapidly expanding urbanization. Plant diversity and abundance as well as the percentage of alien species were recorded in plots on four 20-km long transect lines running from the city centre to the rural surroundings. Various habitat and landscape characteristics were assessed along the transect lines to describe the urban–rural gradient. Based on the results of a principal component analysis considering these landscape characteristics the variable “distance to the city centre” was used as proxy for the urban–rural gradient. Plant diversity increased with increasing distance to the city centre and was also influenced by the type of land use (ornamentally managed, agricultural or unmanaged land) and the percentage cover of built-up area within a 500m radius. The percentage of alien species decreased from 45% in the city centre to 23% in the rural surroundings. The percentage of species belonging to different plant life forms and to different evolutionary strategies were affected by different landscape characteristics. The study showed that the combined effects of expanding urbanization and agricultural land-use changes altered the plant species composition.