Carbon Dioxide Dynamics and Controls in a Deep-water Wetland on the Qinghai-Tibetan Plateau |
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Authors: | Mitsuru Hirota Yanhong Tang Qiwu Hu Shigeki Hirata Tomomichi Kato Wenhong Mo Guangmin Cao Shigeru Mariko |
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Institution: | (1) National Institute for Environmental Studies, Onogawa 16-2, Tsukuba Ibaraki, 305-8506, Japan;(2) Northwest Plateau Institute of Biology, Chinese Academy of Science, Xining, 810001, People’s Republic of China;(3) Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba Ibaraki, 305-8572, Japan;(4) Frontier Research Center for Global Change, 3173-25 Showa-machi, Kanazawa-ku, Yokohama City Kanagawa, 236-0001, Japan;(5) Institute of Biological Sciences, University of Tsukuba, Tsukuba Ibaraki, 305-8572, Japan |
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Abstract: | To initially characterize the dynamics and environmental controls of CO2, ecosystem CO2 fluxes were measured for different vegetation zones in a deep-water wetland on the Qinghai-Tibetan Plateau during the growing
season of 2002. Four zones of vegetation along a gradient from shallow to deep water were dominated, respectively by the emergent
species Carex allivescens V. Krez., Scirpus distigmaticus L., Hippuris vulgaris L., and the submerged species Potamogeton pectinatus L. Gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) were markedly different
among the vegetation zones, with lower Re and GPP in deeper water. NEP was highest in the Scirpus-dominated zone with moderate water depth, but lowest in the Potamogeton-zone that occupied approximately 75% of the total wetland area. Diurnal variation in CO2 flux was highly correlated with variation in light intensity and soil temperature. The relationship between CO2 flux and these environmental variables varied among the vegetation zones. Seasonal CO2 fluxes, including GPP, Re, and NEP, were strongly correlated with aboveground biomass, which was in turn determined by water
depth. In the early growing season, temperature sensitivity (Q10) for Re varied from 6.0 to 8.9 depending on vegetation zone. Q10 decreased in the late growing season. Estimated NEP for the whole deep-water wetland over the growing season was 24 g C m−2. Our results suggest that water depth is the major environmental control of seasonal variation in CO2 flux, whereas photosynthetic photon flux density (PPFD) controls diurnal dynamics. |
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Keywords: | alpine ecosystem aquatic plants NEP water depth wetland zonal vegetation |
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