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An integrated approach considering physiological- and biophysical-based indicators for assessing tolerance of roadside plantations of Alstonia scholaris towards urban roadside air pollution: an assessment of adaptation of plantations for mitigating roadside air pollution

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An integrated approach of physiological- and biophysical-based indicators was used to assess the tolerance of roadside plantations of Alstonia scholaris towards urban roadside air pollution caused due to heavy traffic movements. It was inferred that A. scholaris is a tolerant species to vehicular emissions and can be used to develop roadside plantations and other green spaces in an urban setup.

Abstract

Vehicles are a significant source of pollution affecting the urban environment. Roadside plantations are one of the first defense lines to minimize the impacts of air pollution; at the same time, they also suffer from the adverse effects of pollution. In the present study, an integrated approach, i.e., a combination of physiological, morphological, and biochemical indicators, was used to evaluate the tolerance of roadside plantations of A. scholaris exposed to road traffic emissions. Multiple indicator traits of adaptation and mitigation, especially biophysical (leaf thickness—LTh, dust load flux—DLF, and local cooling created by canopy—CI), physiological (CO2 assimilation rate—A, transpiration—E, stomatal conductance-gs, water use efficiency—WUE, and relative water content—RWC), and biochemical (proline—PROL, soluble sugars—SoS, ascorbic acid—AsA, leaf pH, and total chlorophyll—TChl, accumulation of heavy metals—Fe, Pb, Cd, Cr, and Cu) were used for evaluating the response to air pollutants. Besides, tolerance indices, i.e., air pollution tolerance index (APTI) and anticipated performance index (API), were developed to assess the species suitability for mitigating urban air pollution. It was observed that vehicular emissions modulate the measured functional traits in this species. Plants exposed to the polluted environment have increased LTh, DLF, CI, WUE, PROL, AsA, pH, SoS, heavy metals, while a decrease in the level of A, E, Gs, TChl, and RWC was reported. Further, it was inferred that A. scholaris is a tolerant species and can be suggested for roadside plantations to mitigate vehicular air pollution. The present study is expected to assist the evaluation of other species for adaptation and mitigation of vehicular emissions.

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Acknowledgements

The author is grateful to the Director, Forest Research Institute, Dehradun, for facilitating this study. The author is thankful to the anonymous reviewer for providing valuable suggestions to improve the manuscript's structure.

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    Hukum Singh

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Singh, H. An integrated approach considering physiological- and biophysical-based indicators for assessing tolerance of roadside plantations of Alstonia scholaris towards urban roadside air pollution: an assessment of adaptation of plantations for mitigating roadside air pollution. Trees 37, 69–83 (2023). https://doi.org/10.1007/s00468-021-02179-8

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