School of Geographic Sciences, East China Normal University, Shanghai 200241, China; International Center for Climate and Global Change Research, College of Forestry, Wildlife and Environment, Auburn University, Auburn, AL 36832, United States of America.
International Center for Climate and Global Change Research, College of Forestry, Wildlife and Environment, Auburn University, Auburn, AL 36832, United States of America; Schiller Institute for Integrated Science and Society, Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, United States of America.
Water Res. 2022 Oct 1;224:119043. doi: 10.1016/j.watres.2022.119043. Epub 2022 Sep 1.
Inland waters (rivers, lakes, and reservoirs) have been recognized as hotspots of methane (CH) emissions. However, the magnitude and spatiotemporal pattern of CH emissions and their underlying mechanisms remain largely unknown due to a lack of process-based quantification of CH production, consumption, and evasion within the aquatic ecosystem. Here we developed a process-based aquatic CH module within the framework of the Dynamic Land Ecosystem Model (DLEM) to explicitly simulate inland water carbon fluxes and the associated CH processes. We further applied this model to assess the inland-water CH emissions across the conterminous United States (CONUS) as affected by the climate variability, land use, fertilizer nitrogen (N) application, atmospheric N deposition, and rising atmospheric CO concentration during 1860-2019. The inland water CH emissions across the CONUS had doubled from the 1860s (1.65±0.18 Tg CH-C∙yr) to the 2010s (3.73±0.36 Tg CH-C∙yr). In the 2000s, inland water accounts for 8% of the regional CH budget that offsets 11∼14% of the terrestrial C uptake across the CONUS. Our study showed that the small headwater streams (1 -3 order) account for 49% of the diffusive CH, and reservoirs constitute 50% of the ebullitive CH emissions during the 2010s. Climate change and variability played a dominant role in the increased CH emissions from rivers and lakes. This study implies that effective mitigation strategies to reduce CH4 emissions should pay much attention to global climate change and headwater stream management.
内陆水域（河流、湖泊和水库）已被认为是甲烷（CH）排放的热点地区。然而，由于缺乏对水生生态系统中 CH 生产、消耗和逸出过程的基于过程的量化，这些排放的规模、时空格局及其潜在机制在很大程度上仍不清楚。在这里，我们在动态陆地生态模型（DLEM）的框架内开发了一个基于过程的水生 CH 模块，以明确模拟内陆水碳通量和相关的 CH 过程。我们进一步应用该模型评估了 1860-2019 年期间气候变率、土地利用、化肥氮（N）施用量、大气 N 沉降和大气 CO 浓度升高对美国本土内陆水域 CH 排放的影响。1860 年代至 2010 年代，美国本土内陆水域 CH 排放量增加了一倍，从 1.65±0.18Tg CH-C·yr 增加到 3.73±0.36Tg CH-C·yr。在 2000 年代，内陆水域占区域 CH 预算的 8%，抵消了美国本土 11∼14%的陆地 C 吸收量。我们的研究表明，小型源头溪流（1-3 级）占扩散 CH 的 49%，而水库在 2010 年代构成了逸出 CH 排放的 50%。气候变化和变率在河流和湖泊 CH 排放增加中发挥了主导作用。本研究表明，为减少 CH4 排放而采取的有效缓解策略应高度重视全球气候变化和源头溪流管理。
