Thursday, August 6, 2009

PS 74-179: Biogenic emission in urban ecosystems: Exploring isoprene emission in ornamental bamboo

Andrea N. Melnychenko and Todd N Rosenstiel. Portland State University


Biogenic emissions of volatile organic compounds (VOCs) are a critical and often overlooked aspect of air quality in urban ecosystems. Species compositions in urban settings are heavily influenced by anthropogenic introductions of non-native plants intended for a variety of purposes, however little regard is given to horticultural plantings and atmospheric interactions within urban ecosystems. Isoprene is the most abundant non-methane VOC released from plant leaves to the atmosphere, and in the presence of anthropogenic pollution biogenic VOCs can lead to the formation of tropospheric ozone and seed the formation of secondary aerosol particles. The movement towards urban greening has grown in popularity in cities like Portland, with bamboos playing an ever-increasing number of roles in landscape, horticulture, and urban screening. Additionally, bamboo is grown throughout the world as a source of biomass for textiles and flooring, with growing attention for uses as a carbon sink. Beyond preliminary surveys little has been done to characterize VOC emission within the tribe Bambuseae. Results/Conclusions Here we present results of the most extensive characterization to date of isoprene emission from 25 genera, 72 species, and 95 varieties of ornamental bamboo. Surprisingly, we found a high degree of variability in isoprene emission rates across genera and among species within genera. In general, fast-growing monopodial (running) genera such as Phyllostachys, to which common horticultural varieties of black bamboo and golden bamboo belong, were found to emit significant quantities of isoprene (average: 581 nmol isoprene g DW-1 h-1), while sympodial (clumping) bamboos were found to emit relatively small amounts of this volatile hydrocarbon (average: 87 nmol isoprene g DW-1 h-1). Results from this study indicate that horticultural varieties of bamboo vary greatly with respect to isoprene emission potential. This extreme variation in basal isoprene emission will be related to variation in fundamental drivers of leaf isoprene emission, including leaf respiration rate, isoprene synthase activity, and variation in supply of isoprene precursor metabolites. Results from this study suggest that bamboo is likely to be an important model system for studying the impacts of isoprene emission in urban ecosystems and for examining the physiological mechanisms that dictate a wide range of basal isoprene emission rates.