Physiological response of urban greening shrubs to atmospheric particulate matter pollution: An integral view of ecosystem service and plant function

Abstract

A prominent ecosystem service provided by urban greening plants is the mitigation of air pollution. Plants can intercept atmospheric particulate matter through leaf absorption. However, the foliar dust can cause environmental stress to plant photosynthesis and induce the degradation of plant function. The present study evaluated the dust retention capacity of 8 common greening shrub species of North China (also the representative greening shrub species in Qingdao City) including 4 evergreen species (Pyracantha fortuneana (Maxim.) Li, Buxus megistophylla Levl., Photinia × fraseri Dress, Buxus microphylla Sieb. et Zucc.), and 4 deciduous species (Ligustrum × vicaryi Rehder, Berberis thunbergii ‘Atropurpurea’, Rosa multiflora Thunb. and Sorbaria sorbifolia L.A.Br) with exposure to different pollution sources including clean dust, oil-fired dust and coal-fired dust using a manipulative experiment. Furthermore, a plethora of ecophysiological parameters correlated with photosynthesis and stress tolerance were measured following the dust retention. Within a 30 days of monitoring, the dust retention of different species increased with the time extension and reached a stable status after 20 days. Comprehensively, B. megistophylla had the best performance in dust retention since this species ranked 1st in the dust retention per unit area under the pollution of clean dust and coal-fired dust and ranked 2nd in that under the pollution of oil-fired dust. Evergreen shrub species generally performed better in dust retention than deciduous shrub species. Hence, evergreen shrub species may be prior to deciduous shrub species in the plant selection for urban greening if the ecosystem service of air purification is set as the central goal. The photosynthetic efficiency decreased with the increasing dust retention since the foliar dust blocked the light interception and gas exchange. However, the physiological parameters correlated with stress tolerance showed a whale-humped curve with the increasing dust retention and the self-protection mechanism gradually degraded after 15 days for the 8 species. Overall, dust retention and physiological traits were significantly correlated.