The carbon dioxide evasion cycle of an intermittent first-order stream: contrasting water–air and soil–air exchange
The carbon dioxide evasion cycle of an intermittent first-order stream: contrasting water–air and soil–air exchange
复制标题
间歇性一级河流的二氧化碳逃逸循环：对比水-空气和土壤-空气交换
作者：
Arun Looman;D. Maher;E. Pendall;A. Bass;I. Santos
短暂的溪流和湿地的特点是复杂的浸没和浮出循环，这会影响温室气体通量率。在这项研究中，我们量化了跨越 56 天的三个连续干湿循环中间歇性一级河流的 CO2 和 CH4 浓度和通量的时空变化，以评估水文相变如何影响温室气体逃逸。水柱过量 CO2 范围为 -11 至 1600 μM，过量 CH4 范围为 1 至 15 μM。考虑湿河床水力半径与干河床水力半径之比的时间变化后，总 CO2–C 通量范围为 12 至 156 mmol m−2 day−1，综合日平均值为 61 ± 25 mmol m−2 day−1。土壤-空气逃逸率大约等于水-空气逃逸率。由于静止水域中气体传输速度的增加，降雨使背景水-空气 CO2-C 通量增加了 780%。在最初较长的湿循环期间，CH4–C 通量增加了 19 倍，从 0.1 mmol m−2 day−1 增加到 1.9 mmol m−2 day−1。水深的时间变化和特定地点的短暂性是贾米森溪上游水道碳动态的关键驱动因素。基于这些发现，我们假设来自频繁间歇性溪流（干湿循环从几天到几周）和季节性短暂水道（一次干燥数月）的生物气体通量的循环周期可能有所不同，因此在将瞬态系统纳入区域碳预算和全球变化模型时应考虑这些差异。
Ephemeral streams and wetlands are characterized by complex cycles of submersion and emersion, which influence the greenhouse gas flux rates. In this study we quantify the spatiotemporal variability in CO2 and CH4 concentrations and fluxes of an intermittent first-order stream over three consecutive wet and dry cycles spanning 56 days, to assess how hydrologic phase transitions influence greenhouse gas evasion. Water column excess CO2 ranged from −11 to 1600 μM, and excess CH4 from 1 to 15 μM. After accounting for temporal changes in the ratio of wet versus dry streambed hydraulic radius, total CO2–C fluxes ranged from 12 to 156 mmol m−2 day−1, with an integrated daily mean of 61 ± 25 mmol m−2 day−1. Soil–air evasion rates were approximately equal to those of water–air evasion. Rainfall increased background water–air CO2–C fluxes by up to 780% due to an increase in gas transfer velocity in the otherwise still waters. CH4–C fluxes increased 19-fold over the duration of the initial, longer wet-cycle from 0.1 to 1.9 mmol m−2 day−1. Temporal shifts in water depth and site-specific ephemerality were key drivers of carbon dynamics in the upper Jamison Creek watercourse. Based on these findings, we hypothesise that the cyclic periodicity of fluxes of biogenic gases from frequently intermittent streams (wet and dry cycles ranging from days to weeks) and seasonally ephemeral watercourses (dry for months at a time) are likely to differ, and therefore these differences should be considered when integrating transient systems into regional carbon budgets and models of global change.
影响因子：
18.3
作者：
Borges, Alberto V.;Darchambeau, Francois;Bouillon, Steven
通讯作者：
Bouillon, Steven