Cross-evaluation of measurements of peatland methane emissions on microform and ecosystem scales using high-resolution landcover classification and source weight modelling
Cross-evaluation of measurements of peatland methane emissions on microform and ecosystem scales using high-resolution landcover classification and source weight modelling
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DOI：
10.1016/j.agrformet.2011.02.006
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发表时间：
2011-07-15
影响因子：
6.2
通讯作者：
Wilmking, Martin
中科院分区：
文献类型：
--
作者：
Forbrich, Inke;Kutzbach, Lars;Wilmking, Martin
采用涡度相关法和封闭箱法分别在生态系统尺度和微形态尺度上对贫营养沼泽复合体的甲烷交换进行了研究。有关感兴趣区域和每个30分钟EC通量源区域中三种不同微形态类型分布的信息来自高分辨率（1 m（2））土地覆盖图以及分析源权重模型（Kormann和Meixner，2001）。尽管个别30分钟EC源区之间的微形态覆盖率存在很大差异，但EC源区中的斑点、草坪和丘状微形态的平均加权覆盖率（0.3%：57%：43%）密切反映了感兴趣区域中的总体分布（0.5%：50.1%：49.4%）。测量的生态系统通量拟合的总和，三个缩微通量模型的基础上，环境变量和加权的分数覆盖EC源区。这种方法导致了一个更好的代表性的生态系统通量相比，只有一个通量模型的基础上的方法为整个生态系统（R-2 = 0.87，RMSE = 0.44与R-2 = 0.74，RMSE = 0.61，n = 5181），从而构成了一个成功的缩小规模的测量生态系统尺度通量的缩微尺度。缩小规模和测量的微形态通量的比较显示了良好的协议，草坪微形态和flark和丘微形态的系统差异。差异的原因被认为是有限的分辨率的土地覆盖分类和系统低估的封闭室技术的丘通量。因此，通过降尺度EC通量导出的丘通量被认为比封闭室通量更可靠。根据填隙EC测量得出的季节性生态系统甲烷预算为9.4 +/- 0.2 g CH 4 m（-2）;根据放大缩微测量得出的预算为8.0 +/- 0.8 g CH 4 m（-2）。后者的预算较低的价值是由于低估了flark和丘通量封闭室测量和缩微缺口填充程序。一般来说，从放大缩微测量的估计被认为是不太确定的比从EC测量的估计。(C)2011 Elsevier B. V.保留所有权利。
The methane exchange in an oligotrophic mire complex was measured on the ecosystem and microform scale with the eddy covariance (EC) and the closed chamber technique, respectively. Information about the distribution of three distinct microform types in the area of interest and in each 30 min EC flux source area was derived from a high-resolution (1 m(2)) landcover map in combination with an analytical source weight model (Kormann and Meixner, 2001). The mean weighted coverage of flark, lawn and hummock microforms in the EC source area (0.3% : 57% :43%) closely mirrors the overall distribution in the area of interest (0.5% : 50.1%: 49.4%), despite great differences in microform coverage between individual 30 min EC source areas. The measured ecosystem flux was fitted to the sum of three microform flux models based on environmental variables and weighted by their fractional coverage in the EC source area. This method resulted in a better representation of the ecosystem flux compared to an approach based on only one flux model for the whole ecosystem (R-2 = 0.87, RMSE = 0.44 vs. R-2 = 0.74, RMSE = 0.61, n = 5181) and thus constitutes a successful down-scaling of measured ecosystem scale flux to the microform scale. A comparison of down-scaled and measured microform fluxes reveals a good agreement for lawn microforms and systematic differences for flark and hummock microforms. Reasons for the differences are thought to be the limited resolution of the landcover classification and the systematic underestimation of hummock fluxes by the closed chamber technique. As a result, hummock fluxes derived by down-scaling of EC fluxes are considered to be more dependable than closed chamber fluxes. The seasonal ecosystem methane budget from gap-filled EC measurements was 9.4 +/- 0.2 g CH4 m(-2); the budget derived from up-scaled microform measurements was 8.0 +/- 0.8 g CH4 m(-2). The lower value of the latter budget is attributed to the underestimation of flark and hummock fluxes by closed chamber measurements and to the microform gap-filling procedure. Generally, estimates from up-scaled microform measurements are found to be less certain than estimates from EC measurements. (C) 2011 Elsevier B.V. All rights reserved.