Responses of functional traits of leaves and reproductive efforts in silver birch under an urban air pollution gradient

Urban vegetation is a fundamental element and the keystone of urban ecological systems. Significant air pollution can affect plant functional traits. In this work we study the response of selected leaf functional traits (leaf pigments concentration, leaf area, specific leaf area, relative water content) and reproductive effort (no of staminate inflorescences, no of fructifications, seeds no, no and length of fructification axes) of pioneer tree, Betula pendula Roth to air pollution stress in the urban ecosystem. 21 trees in 3 zones, growing under different long-term air PM2.5 and PM10 (particulate matter ø ≤ 2.5 μm and ø ≤ 10 μm, respectively) concentration, land use and two seasons were studied. We confirmed air pollution stress has a profound effect on selected plant traits. The leaf chlorophyll b (Chl b) content, specific leaf area, and relative water content are highest in most polluted city centre and decrease to the peripheries, while chlorophyll a remains constant over zones. Moreover, the reproductive effort measured by the number and length of fructification axes were lowest in city centre. Overall the consistent patterns of variation of Chl b and reproductive effort in birch across gradient studied underscore their usability as easy to measure and low cost indicators of air quality in urban environments.