The measurement of net ecosystems methane (CH4) exchange (NEE-CH4) by eddy covariance is of vital importance for the evaluation of the source or sink strength of upland and wetland ecosystems. However, uncertainties remain in the magnitudes and the drivers of NEE-CH4 in upland and wetland ecosystems. Here, we conducted a data-synthesis using 472 site-year NEE-CH4 data from 126 sites on a global scale to explore the patterns of NEE-CH4 in uplands and wetlands and their driving factors. We found that, across the study sites, upland ecosystem act as a weak CH4 source with annual NEE-CH4 rate as 1.64 ± 0.24 g C m−2 year−1, which was significantly lower than in wetland ecosystems (19.35 ± 1.00 g C m−2 year−1). Meanwhile, the NEE-CH4 in inland wetlands (20.18 ± 1.06 g C m−2 year−1) was significantly high than in coastal wetlands (9.17 ± 1.67 g C m−2 year−1). NEE-CH4 in anthropogenically perturbed wetlands was significantly higher than in natural wetlands. In upland ecosystems, the NEE-CH4 was positively correlated with mean annual temperature (MAT). While, in wetland ecosystems, the water table depth (WTD) and MAT were the two most important predictors for NEE-CH4, with higher WTD and MAT corresponding to higher NEE-CH4. The NEE-CH4 in wetland ecosystems was also positively associated with gross primary productivity (GPP), ecosystem respiration (ER) and net ecosystem carbon dioxide exchange (NEE-CO2). Compared with upland ecosystems, NEE-CH4 played a more important role in regulating the C source or sink strength of wetland ecosystems. Overall, our results shed light on the magnitudes and the drivers of NEE-CH4 in upland and wetland ecosystems, which could help better understanding and prediction of CH4 budget in terrestrial ecosystems.

中文翻译：

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全球高地和湿地生态系统中甲烷的生态系统-大气交换


涡度相关差测量生态系统甲烷净交换 （NEE-CH4） 对于评价高地和湿地生态系统的源或汇强度至关重要。然而，NEE-CH4 在高地和湿地生态系统中的量级和驱动因素仍然存在不确定性。在这里，我们使用来自全球 126 个站点的 472 个站点年 NEE-CH4 数据进行了数据合成，以探索高地和湿地中 NEE-CH4 的模式及其驱动因素。我们发现，在整个研究地点中，高地生态系统是一个弱 CH4 来源，年均 NEE-CH4 速率为 1.64 ± 0.24 g C m-2 年-1，显著低于湿地生态系统（19.35 ± 1.00 g C m-2 年-1）。同时，内陆湿地的 NEE-CH4 （20.18 ± 1.06 g C m-2 year-1） 显著高于沿海湿地 （9.17 ± 1.67 g C m-2 year-1）。人为扰动湿地的 NEE-CH4 显著高于自然湿地。在高地生态系统中，NEE-CH4 与年平均温度 （MAT） 呈正相关。而在湿地生态系统中，地下水位深度 （WTD） 和 MAT 是 NEE-CH4 的两个最重要的预测因子，较高的 WTD 和 MAT 对应于较高的 NEE-CH4。湿地生态系统中的 NEE-CH4 也与总初级生产力 （GPP） 、生态系统呼吸 （ER） 和生态系统二氧化碳净交换 （NEE-CO2） 呈正相关。与高地生态系统相比，NEE-CH4 在调节湿地生态系统的 C 源或汇强度方面发挥着更重要的作用。总体而言，我们的结果揭示了 NEE-CH4 在高地和湿地生态系统中的大小和驱动因素，这可能有助于更好地理解和预测陆地生态系统中的 CH4 收支。