Nitrous oxide fluxes from the littoral zone of a lake on the Qinghai-Tibetan Plateau
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Nitrous oxide (N2O) fluxes were measured in six littoral mirco-zones of Lake Huahu on Qinghai-Tibetan Plateau in the peak growing season of years of 2006 and 2007. The weighted mean N2O flux rate was 0.08 mg N m − 2 h − 1 (ranged from −0.07 to 0.35 mg N m − 2 h − 1). The result was relatively high in the scope of N2O fluxes from boreal and temperate lakes. Emergent plant zones (Hippuris vulgaris and Glyceria maxima stands) recorded the highest N2O flux rate (0.11 ± 0.24 and 0.08 ± 0.17 mg N m − 2 h − 1, respectively). Non-vegetated lakeshore recorded the lowest N2O flux (0.03 ± 0.11 mg N m − 2 h − 1), lower than that from the floating mat zone of Carex muliensis (0.05 ± 0.18 mg N m − 2 h − 1), the floating-leaved plant zone of Polygonum amphibium (0.07 ± 0.11 mg N m − 2 h − 1), and the wet meadow (0.07 ± 0.15 mg N m − 2 h − 1). Standing water depths were important factors to explain such spatial variations in N2O fluxes. Significant temporal variations in N2O fluxes were also found. Such temporal variation in N2O flux in the littoral zone may be dependent on the interaction of water regime and thermal conditions, instead of the latter solely. These results showed the importance of the littoral zone of lake, especially the emergent plant zone, as a hotspot of N2O fluxes in such grazing meadows.
KeywordsZoige plateau Greenhouse gases fluxes Littoral wetlands N2O budget Nitrogen cycling Lake
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