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Ecosystem carbon isotopic discrimination in a cool-temperate deciduous forest using leaf wax biomarkers-aerosol approach.

KONDO, Miyuki*,1, UCHIDA, Masao2, MURAYAMA, Shohei3, KUMATA, Hidetoshi4, Shibata, Yasuyuki5, KOIZUMI, Hiroshi1, 1 Institute for Basin Ecosystem Studies, Gifu, Gifu, Japan2 Institute of Observational Reseach for Global Change, Yokosuka, Kanagawa, Japan3 Institute for Environmental Management Technology, Tsukuba, Ibaragi, Japan4 Laboratory of Environ Chemistry, Hachioji, Tokyo, Japan5 Environmental Chemistry Division, Tsukuba, Ibaragi, Japan

ABSTRACT- Accurate estimates of carbon isotopic discrimination () by photosynthesis are important in evaluating the magnitude and spatial distribution of the terrestrial uptake of carbon dioxide. Very little is known about the temporal and regional pattern of discrimination in terrestrial biosphere because it is subject to considerable uncertainty. In this study, we measured the molecular carbon isotopic composition (13C) of plant wax in aerosol in order to estimate direct mean values at the ecosystem-level and with less than monthly temporal resolution. We collected bulk aerosols samples from August 2003 to November 2004 during the growing season at Takayama Experimental Site (36°8’N, 137°6’E, 1420m a.s.l.) in a cool-temperate deciduous forest in Japan. Sampling duration ranged between 10 days and 27 days. We analyzed the molecular and 13C values of major wax compound classes (n-alkanols, n-alkanoic acids and n-Alkanes) in dominant species (Betula ermanii, Quercus crispula, Sasa senanensis) and in aerosols collected at a position 2m-height above the ground and also measured 13C of bulk air above the forest canopy. Concentrations of C23-C32 n-Alkanes in aerosols collected in the forest ranged from 0.85 ng / m3 air (average of per 10 days samples) to 1.16ng / m3 air (average of per 19 days samples) during the growing season in 2003. Mean 13Cof n-Alkanes (C27, C29 and C31) ranged from –30.0 ±0.4‰ to –33.9 ±1.8 ‰ in 2003. By using the leaf wax 13C, the magnitude of was estimated from 15.8‰ to 19.5‰ in 2003

Key words: Ecosystem carbon isotope discrimination, Aerosols, Leaf wax biomarker, cool-temperate deciduous forest

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