Effects of seasonal inundation on methane fluxes from forested freshwater wetlands
Effects of seasonal inundation on methane fluxes from forested freshwater wetlands
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DOI：
10.1088/1748-9326/ac1193
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发表时间：
2021
影响因子：
6.7
通讯作者：
K. Hondula;C. N. Jones;M. Palmer
中科院分区：
文献类型：
--
作者：
K. Hondula;C. N. Jones;M. Palmer
小型淡水生态系统的甲烷排放是全球甲烷预算中最大的不确定性因素之一。虽然已知这些系统相对于其规模产生大量甲烷，但量化其排放的时间，幅度和空间范围仍然具有挑战性。我们开始，以解决这一挑战，在季节性淹没森林矿质土壤湿地（1）测量湿地甲烷通量和水文制度在淹没和非淹没土壤，（2）湿地水文制度如何影响甲烷排放源区域的空间范围的特征，（3）模拟平均每日湿地规模的通量率使用四种不同的放大技术。我们的研究结果表明，淹没的范围和持续时间，而不是频率或深度，湿地甲烷排放的主要驱动力。此外，我们发现，甲烷通量最好用水位变化的方向（即上升或下降）来描述，当水位下降时，排放量通常较高。一旦土壤被淹没，随后的水位变化并不能解释观测到的静水中甲烷浓度的变化。最后，我们的空间模型表明，代表淹没和相关的甲烷源区是一个关键步骤，估计当地到区域尺度的甲烷排放量。间歇性淹没的土壤交替之间的源和汇的甲烷取决于水位，土壤湿度和水位变化的方向。这些结果表明，量化季节性淹没的森林淡水湿地的水文制度，使甲烷排放量的更准确的估计。
Methane emissions from small freshwater ecosystems represent one of the largest components of uncertainty in the global methane budget. While these systems are known to produce large amounts of methane relative to their size, quantifying the timing, magnitude, and spatial extent of their emissions remains challenging. We begin to address this challenge in seasonally inundated forested mineral soil wetlands by (1) measuring wetland methane fluxes and hydrologic regime across both inundated and non-inundated soils, (2) characterizing how wetland hydrologic regime impacts the spatial extent of methane emission source areas, and (3) modeling average daily wetland-scale flux rates using four different upscaling techniques. Our results show that inundation extent and duration, but not frequency or depth, were major drivers of wetland methane emissions. Moreover, we found that methane fluxes were best described by the direction of water level change (i.e. rising or falling), where emissions were generally higher when water levels were falling. Once soils were inundated, subsequent changes in water level did not explain observed variability of methane concentrations in standing water. Finally, our spatial modeling suggests that representing inundation and associated methane source areas is a critical step in estimating local to regional scale methane emissions. Intermittently inundated soils alternated between being sources and sinks of methane depending on water level, soil moisture, and the direction of water level change. These results demonstrate that quantifying the hydrologic regime of seasonally inundated forested freshwater wetlands enables a more accurate estimation of methane emissions.