The influence of urban stress factors on responses of ground cover vegetation.

A comprehensive study was conducted to evaluate the effects of ambient air pollution, land use, and soil properties on ground cover vegetation in the urban area of Varanasi city, situated in the Indo Gangetic Plain of India. Twelve leaf functional traits were assessed on eight most dominant herbaceous species belonging to four angiospermic families in three different land uses with varying air pollution loads and soil properties. Particulate matter (PM10 and TSP), gaseous pollutants (SO2, NO2, and O3), land uses (built-up area, shrub, and grass cover), and soil properties showed significant variability among the land uses. Air pollution was identified as the major stress factor which influenced leaf functional traits of ground cover vegetation followed by soil properties and land uses. Among the plants, Croton sparsiflorus was found to be the most responsive plants to all the factors. Plants responded differently under varying environmental factors as Euphorbia hirta was maximally influenced by air pollution, whereas the effect of land use was maximum in C. sparsiflorus. Influence of soil properties was highest in Digitaria ciliaris and Scoparia dulcis. All the environmental factors in combination maximally influenced non-enzymatic antioxidants (ascorbic acid and polyphenolics) followed by photosynthetic pigments among the different leaf functional traits. Among the environmental factors, NO2 and PM were identified as the most influencing factors regulating leaf functional traits followed by K level in soil and shrub cover. It can be concluded that responses of different leaf functional traits of ground cover vegetation varied with different environmental factors and responses were mostly species specific.