Abstract
Urbanization contributes to extensive land use changes and environmental degradation which may influence changes in soil properties. These abiotic changes may aggravate invasions and favour the distribution and number of invasive species in urban areas which could negatively impact biodiversity. This case study was, therefore, undertaken in the metropolitan city of Kolkata to assess the existing plant species richness (both native and exotic) and to determine the relative role of some soil physico-chemical parameters on species richness. Plant species were recorded and soil samples were collected from each study site. The total species richness ranged from 4 to 25 with 50% of sites having a median number of 11 species. The presence of at least 3 or more invasive species was observed in >80% of sites. The mean and median values of soil parameters showed considerable variation in soil properties between sites. Urban soils had elevated pH values and higher available N, P and Ca. Soil available N appeared to be significantly correlated with both total species and exotic (including invasive) species richness while available phosphorus showed significant correlation with only exotic species richness. The GLM Poisson log-linear models showed a significant positive relationship of soil N with total species richness and exotic richness including invasive species richness in the study area.
Highlights
The surface soil in these areas get mixed and is covered by artificial impervious surfaces, due to the mechanical and/or chemical disturbance associated with urbanization, which may cause an irreversible loss of many soil properties and functions [5]
The median values, which are more robust to outliers than the mean, were 11, 5 and 5 for total species richness, native species and exotic species numbers respectively
When the sites were judged for richness patterns based on the median values, 50% of sites showed total species richness ≥ 11 indicating a good number of species in many urban sites
Summary
Urban soils contain large pools of carbon, nitrogen and other elements which help to support plant growth and sustain biogeochemical cycles [6]. They provide an array of ecosystem services like reducing bioavailability of pollutants, habitats for soil and plant biota, microclimate regulation and food production [7] [8] [9]. This study was, undertaken in the metropolitan city of Kolkata to assess 1) the species richness (both native and exotic) within this area and 2) to determine the relative role of some physico-chemical factors in influencing the existing plant species richness
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