FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands
FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands
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DOI：
10.5194/essd-13-3607-2021
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发表时间：
2021-07-29
影响因子：
11.4
通讯作者：
Jackson, Robert B.
中科院分区：
文献类型：
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作者：
Delwiche, Kyle B.;Knox, Sara Helen;Jackson, Robert B.
来自自然景观的甲烷（CH 4）排放量约占全球大气CH 4排放量的一半，但排放量和驱动因素的绝对数量和季节性仍存在很大的不确定性。涡度协方差（EC）测量的CH 4通量是理想的约束生态系统规模的CH 4排放量由于准连续和高时间分辨率的CH 4通量测量，同时二氧化碳，水，能量通量测量，缺乏生态系统的干扰，并在过去的十年中增加了数据集的可用性。在这里，我们（1）描述了新发布的数据集FLUXNET-CH 4 Version 1.0，这是CH 4 EC测量的第一个开源全球数据集（可在https：//fluxnet.org/data/fluxnet-ch4-community-product/获得，最后访问日期：2021年4月7日）。FLUXNET-CH 4包括来自全球79个站点的半小时和每日间隙填充和非间隙填充的总CH 4通量和气象数据：42个淡水湿地，6个半咸水和咸水湿地，7个以前排水的生态系统，7个稻田站点，2个湖泊和15个高地。然后，我们（2）评估FLUXNET-CH 4全球淡水湿地覆盖的代表性，因为FLUXNET-CH 4版本1.0中的大多数站点是淡水湿地，这是大气CH 4排放总量的重要来源;（3）我们提供了淡水湿地CH 4通量的季节变化和季节性预测因子的第一个全球估计值。我们的代表性分析表明，淡水湿地网站的数据集涵盖全球湿地生物气候属性（包括能源，水分和植被相关的参数）在北极，寒带和温带地区，但只有稀疏覆盖潮湿的热带地区。湿地甲烷排放量的季节性指标在不同纬度带之间差异很大。在淡水湿地（除南纬20度至北纬20度之间的湿地外），年平均气温每升高1 ℃，春季甲烷排放量开始升高的时间提前3 d，甲烷排放季节延长4 d。平均而言，春季甲烷排放量的增加滞后于土壤变暖1个月，在土壤变暖开始之前，很少有地点的甲烷排放量增加。相比之下，这些地点中大约有一半在春季总初级生产力增加之前经历了春季甲烷排放量上升的开始。夏季CH 4排放高峰的时间与夏季温度高峰或GPP高峰的时间无关。我们的研究结果为CH 4建模提供了季节性参数，并突出了温度或GPP无法预测的季节性指标（即，CH 4峰值的季节性）。FLUXNET-CH 4是诊断和了解陆地生态系统和气候驱动因素在全球CH 4循环中的作用的一个强大的新资源，未来增加热带生态系统的站点和站点年数据收集将为该数据库提供附加值。所有季节性参数可在https://doi.org/10.5281/zenodo.4672601获得（Delwiche等人，2021年）。此外，用于提取季节性参数的原始FLUXNET-CH 4数据可从https://fluxnet.org/data/fluxnet-ch4-community-product/下载（最后访问日期：2021年4月7日），79个单独站点数据DOI的完整列表见本文表2。
Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in the absolute magnitude and the seasonality of emission quantities and drivers. Eddy covariance (EC) measurements of CH4 flux are ideal for constraining ecosystem-scale CH4 emissions due to quasi-continuous and high-temporal-resolution CH4 flux measurements, coincident carbon dioxide, water, and energy flux measurements, lack of ecosystem disturbance, and increased availability of datasets over the last decade. Here, we (1) describe the newly published dataset, FLUXNET-CH4 Version 1.0, the first open-source global dataset of CH4 EC measurements (available at https://fluxnet.org/data/fluxnet-ch4-community-product/, last access: 7 April 2021). FLUXNET-CH4 includes half-hourly and daily gap-filled and non-gap-filled aggregated CH4 fluxes and meteorological data from 79 sites globally: 42 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we (2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage globally because the majority of sites in FLUXNET-CH4 Version 1.0 are freshwater wetlands which are a substantial source of total atmospheric CH4 emissions; and (3) we provide the first global estimates of the seasonal variability and seasonality predictors of freshwater wetland CH4 fluxes. Our representativeness analysis suggests that the freshwater wetland sites in the dataset cover global wetland bioclimatic attributes (encompassing energy, moisture, and vegetation-related parameters) in arctic, boreal, and temperate regions but only sparsely cover humid tropical regions. Seasonality metrics of wetland CH4 emissions vary considerably across latitudinal bands. In freshwater wetlands (except those between 20 degrees S to 20 degrees N) the spring onset of elevated CH4 emissions starts 3 d earlier, and the CH4 emission season lasts 4 d longer, for each degree Celsius increase in mean annual air temperature. On average, the spring onset of increasing CH4 emissions lags behind soil warming by 1 month, with very few sites experiencing increased CH4 emissions prior to the onset of soil warming. In contrast, roughly half of these sites experience the spring onset of rising CH4 emissions prior to the spring increase in gross primary productivity (GPP). The timing of peak summer CH4 emissions does not correlate with the timing for either peak summer temperature or peak GPP. Our results provide seasonality parameters for CH4 modeling and highlight seasonality metrics that cannot be predicted by temperature or GPP (i.e., seasonality of CH4 peak). FLUXNET-CH4 is a powerful new resource for diagnosing and understanding the role of terrestrial ecosystems and climate drivers in the global CH4 cycle, and future additions of sites in tropical ecosystems and site years of data collection will provide added value to this database. All seasonality parameters are available at https://doi.org/10.5281/zenodo.4672601 (Delwiche et al., 2021). Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/ (last access: 7 April 2021), and a complete list of the 79 individual site data DOIs is provided in Table 2 of this paper.