Radiative forcing of methane emission completely offsets net carbon dioxide uptake in a temperate freshwater marsh from the present to future
Radiative forcing of methane emission completely offsets net carbon dioxide uptake in a temperate freshwater marsh from the present to future
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DOI：
10.1016/j.agrformet.2024.109889
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发表时间：
2024-03
影响因子：
6.2
通讯作者：
Junjie Li;Junji Yuan;Yanhong Dong;Deyan Liu;Yuncai Miao;Cong Yang;Weixin Ding
中科院分区：
文献类型：
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作者：
Junjie Li;Junji Yuan;Yanhong Dong;Deyan Liu;Yuncai Miao;Cong Yang;Weixin Ding
湿地具有二氧化碳（CO2）汇和甲烷（CH4）源的双重功能。长期以来，人们一直认为湿地的ch4排放可能抵消二氧化碳吸收的净冷却效应，但目前和未来气候条件下湿地二氧化碳和ch4通量的权衡缺乏详细的知识。本研究利用涡旋相关方差技术测量了2020 - 2023年澳大利亚芦苇（aPhragmites australis）占主导地位的淡水沼泽生态系统尺度的co2和ch4通量。此外，我们基于4种代表性浓度路径（RCP）下的6种地球系统模式预测了未来的co2和ch4通量。我们的研究结果表明，p。澳大利亚沼泽是一个巨大的co2汇和ch4排放热点，3年年平均净co2吸收量为926 g co2 - 2， ch4排放量为42 g CH4m-2。二氧化碳吸收造成的负辐射强迫被湿地ch4排放完全抵消，导致100年平均年净co2当量（CO2-eq m - 2）排放量为970 g。净co2当量通量的年际变化受水文变化驱动，干旱年净co2当量通量较低。在未来的情景中，ch4排放的辐射强迫可以持续和完全抵消淡水沼泽的净co2吸收。令人担忧的是，在RCP8.5情景下，未来净co2当量通量呈现出显著增加的趋势，因为ch4排放比co2吸收对温度升高和降水的响应更大。相反，在RCP2.6情景下，未来净co2当量通量呈现明显的下降趋势，这主要是由于暖化湿地ch4正反馈的减缓和辐射驱动的co2吸收的持续上升。总体而言，我们的研究结果肯定了湿地在封存大气co2中的作用，但强调了湿地ch4排放在调节湿地-气候反馈中的当前和日益重要的作用。
Wetlands serve a dual function as carbon dioxide (CO2) sinks and methane (CH4) sources. Emissions of CH4from wetlands have long been considered to potentially offset net cooling effect of CO2uptakes, yet there is a paucity of detailed knowledge on the tradeoff of wetland CO2and CH4fluxes under current and future climate conditions. This study used the eddy covariance technique to measure ecosystem-scale CO2and CH4fluxes in aPhragmites australis-dominated freshwater marsh from 2020 to 2023. Furthermore, we projected future CO2and CH4fluxes based on six Earth System Models under four Representative Concentration Pathways (RCP). Our results show that theP. australismarsh is a large CO2sink and a hotspot for CH4emissions, with a 3-year annual average net CO2uptake of 926 g CO2m‒2and CH4emission of 42 g CH4m‒2. The negative radiative forcing caused by CO2uptake was entirely counterbalanced by wetland CH4emissions, resulting in a mean annual net CO2-equivalent (CO2-eq) emission of 970 g CO2-eq m‒2over a 100-year time horizon. The interannual variability of net CO2-eq fluxes was driven by hydrological variations, with lower net CO2-eq fluxes occurring during dry years. In future scenarios, the radiative forcing of CH4emissions could persistently and completely offset the net CO2uptake in this freshwater marsh. Alarmingly, future net CO2-eq fluxes exhibit a significant increasing trend under the RCP8.5 scenario because CH4emissions are more responsive than CO2uptake to increasing temperatures and precipitation. Conversely, under the RCP2.6 scenario, future net CO2-eq fluxes show a significant downward trend, primarily due to the slowdown of positive warming-wetland CH4feedback and the radiation-driven continuous rise in CO2uptake. Overall, our findings affirm the role of wetlands in sequestrating atmospheric CO2but highlight the current and growing importance of wetland CH4emissions in regulating wetland-climate feedback.