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首页> 外文期刊>Theoretical and applied climatology >Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method
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Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method

机译：使用松弛涡流累积法连续测量落叶松森林中的甲烷通量

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We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO_2 fluxes measured by the eddy covari-ance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of half-hourly methane flux measurements to be approximately 1.2 and 0.7 μg CH_4m~(-2) s~(-1), respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21 μg CH_4m~(-2) s~(-1) on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835±175 mg CH_4m~(-2) year~(-1) (8.35 kg CH_4ha~(-1) year~(-1)), which was comparable to the flux range of 379-2,478 mg CH_4m~(-2) year~(-1) previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.
机译：我们使用放松涡流累积（REA）方法测量了森林冠层全年的甲烷通量。该采样系统经过仔细验证，以验证通过涡度协方差法测量的热量和CO_2通量。尽管采样系统功能强大，但是由于甲烷气体分析仪的精度有限，因此甲烷通量的测量存在很大的不确定性。根据甲烷分析仪信号的频谱特征和垂直风速标准偏差的日变化，我们发现半小时甲烷通量测量的白天和夜间精度分别约为1.2和0.7μgCH_4m〜（- 2）分别为s〜（-1）。据估计，稀释效应引起的其他不确定性每半小时影响精度达0.21μgCH_4m〜（-2）s〜（-1）。观测到的通量存在昼夜变化。在我们的研究中未观察到植物叶片的生物排放，因此在冠层尺度的交换中可以忽略不计。 CH_4m〜（-2）年〜（-1）的年甲烷总沉降量为835±175 mg（8.35 kg CH_4ha〜（-1）年〜（-1）的甲烷量），相当于379-2,478 mg的通量范围CH_4m〜（-2）年〜（-1）以前在其他日本森林土壤中测得。这项研究表明，REA方法可能是一种测量森林上冠层甲烷通量的有前途的技术，但仍需要进一步提高分析仪的精度。

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  • 来源
    《Theoretical and applied climatology》 |2012年第4期|p.461-472|共12页
  • 作者

    Masahito Ueyama; Ken Hamotani; Wataru Nishimura; Yoshiyuki Takahashi; Nobuko Saigusa; Reiko Ide;

  • 作者单位

    Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Japan;

    Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Japan;

    Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Japan;

    National Institute for Environmental Studies, Center for Global Environmental Research, 16-2 Onogawa, Tsukuba, Ibaraki, Japan;

    National Institute for Environmental Studies, Center for Global Environmental Research, 16-2 Onogawa, Tsukuba, Ibaraki, Japan;

    National Institute for Environmental Studies, Center for Global Environmental Research, 16-2 Onogawa, Tsukuba, Ibaraki, Japan;

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