title: Sunlight stimulates methane uptake and nitrous oxide emission from the High Arctic tundra.
abstract: Many environmental factors affecting methane (CH4) and nitrous oxide (N2O) fluxes have been investigated during the processes of carbon and nitrogen transformation in the boreal tundra. However, effects of sunlight on CH4and N2O fluxes and their budgets were neglected in the boreal tundra. Here, summertime CH4and N2O fluxes in the presence and total absence of sunlight were investigated at the six tundra sites (DM1-DM6) on Ny-Ålesund in the High Arctic. The mean CH4fluxes at the tundra sites ranged from -4.7 to -158.6μg CH4m-2h-1in the presence of light, indicating that a large CH4sink occurred in the tundra soils. However, enhanced CH4emission in total absence of light occurred at all the tundra sites. The mean N2O fluxes ranged from 7.4 to 14.6μg N2O m-2h-1in the presence of light, whereas in the absence of light all the tundra sites generally released less N2O, and even significant N2O uptake occurred there. Soil temperature, chamber temperature and soil moisture showed no significant correlations with tundra CH4and N2O flux. The presence of sunlight increased tundra CH4uptake by 114.2μg CH4m-2h-1and N2O emission by 10.9μg N2O m-2h-1compared with total absence of light. Overall our results showed that tundra ecosystem switched from CH4sink and N2O emission source in the presence of light to CH4emission source and N2O sink in the absence of light. Therefore sunlight had an important effect on CH4and N2O budgets in the High Arctic tundra. The exclusion of sunlight might overestimate CH4budgets, but underestimate N2O budgets in the Arctic tundra ecosystem.
authors: Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230036, China.
authors: Fangfang
authors: F
authors: Li
authors: Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230036, China. Electronic address: zhurb@ustc.edu.cn.
authors: Renbin
authors: R
authors: Zhu
authors: Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230036, China.
authors: Tao
authors: T
authors: Bao
authors: Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230036, China.
authors: Qing
authors: Q
authors: Wang
authors: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
authors: Hua
authors: H
authors: Xu
keywords: Arctic region; Greenhouse gases; In presence of light; Methane fluxes; Nitrous oxide fluxes; O(2) availability