Spectral evidence for substrate availability rather than environmental control of methane emissions from a coastal forested wetland
Spectral evidence for substrate availability rather than environmental control of methane emissions from a coastal forested wetland
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DOI：
10.1016/j.agrformet.2020.108062
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发表时间：
2020-09
影响因子：
6.2
通讯作者：
B. Mitra;Kevan J. Minick;G. Miao;J. Domec;Prajaya Prajapati;S. McNulty;G. Sun;J. King;A. Noormets
中科院分区：
文献类型：
--
作者：
B. Mitra;Kevan J. Minick;G. Miao;J. Domec;Prajaya Prajapati;S. McNulty;G. Sun;J. King;A. Noormets
沿海淡水森林湿地，如美国东南部发现的甲烷（CH 4）通量的动态知识仍然有限。本文利用北卡罗来纳州东部天然洼地阔叶树沼泽的数据，研究了生态系统净CH 4交换（NEECH 4）时间序列的光谱特性及其与关键环境条件（温度（Ts 5）、地下水位（WTD）和大气压力（Pa））和生理通量（光合作用（GPP）、蒸腾作用（LE）和液流（Js））的共谱行为。NEECH 4通量在五年（2012 - 2016年）内进行了测量，包括潮湿和干燥年份。在生长季节，CH 4排放与GPP、LEs和Js在日尺度上存在较强的共谱峰。这表明，在后者的过程中，以及理解的昼夜周期可能会影响CH 4生产通过基板的可用性（GPP）和运输（液流和LE）。不同时间序列之间的因果关系是由相移的大小和一致性建立的。Ts 5和Pa的因果效应被排除，因为尽管与CH 4共谱峰，但它们的相位关系不一致。在天气尺度WTDonCH 4流出的波动的影响缺乏明确的因果关系的迹象，可能是由于时间滞后和滞后。与生态系统尺度LE的同谱峰比与Js的同谱峰更强，说明LE的蒸发分量与植物蒸腾的贡献相当。因此，我们的结论是，虽然通过植物的溶解气体的排放可能会发生，它可能不会有助于higherCH 4 emissions已提出的aerenchymatous气体运输莎草湿地。这些研究结果可以为未来的模型开发提供信息，（一）突出植被过程和CH 4排放之间的耦合，（二）为不同的驱动因素确定具体的和不重叠的时间尺度。
Knowledge of the dynamics of methane (CH4) fluxes across coastal freshwater forested wetlands, such as those found in the southeastern US remains limited. In the current study, we look at the spectral properties of ecosystem net CH4exchange (NEECH4) time series, and its cospectral behavior with key environmental conditions (temperature (Ts5), water table (WTD) and atmospheric pressure (Pa)) and physiological fluxes (photosynthesis (GPP), transpiration (LE),sap flux (Js)) using data from a natural bottomland hardwood swamp in eastern North Carolina. NEECH4fluxes were measured over five years (2012 – 2016) that included both wet and dry years. During the growing season, strong cospectral peaks at diurnal scale were detected betweenCH4efflux andGPP, LEandJs. This suggests that the well understood diurnal cycles in the latter processes may affectCH4production through substrate availability (GPP) and transport (sap flow andLE). The causality between different time series was established by the magnitude and consistency of phase shifts. The causal effect ofTs5andPawere ruled out because despite cospectral peaks withCH4, their phase relationships were inconsistent. The effect of fluctuations inWTDonCH4efflux at synoptic scale lacked clear indications of causality, possibly due to time lags and hysteresis. The stronger cospectral peak with ecosystem scaleLErather thanJssuggested that the evaporative component ofLEcontributed equally with plant transpiration. Hence, we conclude that while the emission of dissolved gases through plants likely takes place, it may not contribute to higherCH4emissions as has been proposed by aerenchymatous gas transport in sedge wetlands. These findings can inform future model development by (i) highlighting the coupling between vegetation processes andCH4emissions, and (ii) identifying specific and non-overlapping timescales for different driving factors.