Oquist Mats G, Wallin Marcus, Seibert Jan, Bishop Kevin, Laudon Hjalmar
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden.
Environ Sci Technol. 2009 Oct 1;43(19):7364-9. doi: 10.1021/es900416h.
The aim of this investigation was to determine the lateral exportof dissolved inorganic carbon (DIC) from soils of a Swedish boreal forest to a first order stream and to estimate the partitioning of this DIC into CO2 evasion from the stream surface and the DIC pool exported down through the catchment by streamwater. The groundwater entering the stream was supersaturated with CO2 with values as high as 17 times equilibrium with the atmosphere. Up to 90% of the estimated daily soil DIC export to the stream was emitted to the atmosphere as CO2 within 200 m of the water entering the stream. The annual DIC export from the soil to the stream was estimated to be 3.2 (+/- 0.1) g C m(-2) yr(-1) (normalized to catchment size). Ninety percent of the variation in soil DIC export could be explained by the variation in groundwater discharge and the DIC concentrations per se, were of minor importance. A significant correlation (R(l) = 0.74, P < 0.01) between soil DIC export and CO2 emission from the stream surface suggests that emission dynamics were primarily driven by the export of terrestrial DIC and that in-stream processes were less important. Our results reveal that current budget estimates of lateral DIC export from soils to aquatic conduits need to be revised because they do not account for conditions prevailing in headwater streams. Any quantification of lateral stream C export and CO2 emissions from freshwater systems must include headwater streams as well as the lower parts of the aquatic conduit.
本研究的目的是确定瑞典北方森林土壤中溶解无机碳（DIC）向一级溪流的侧向输出，并估算该DIC在溪流表面逸出的CO₂以及通过溪水向下游流域输出的DIC库之间的分配情况。进入溪流的地下水中CO₂过饱和，其值高达与大气平衡值的17倍。估计每日从土壤侧向输出到溪流的DIC中，高达90%在水流进入溪流后的200米范围内以CO₂的形式排放到大气中。估计每年从土壤侧向输出到溪流的DIC为3.2（±0.1）克碳每平方米每年（按集水区面积归一化）。土壤DIC输出变化的90%可由地下水流量变化来解释，而DIC浓度本身的影响较小。土壤DIC输出与溪流表面CO₂排放之间存在显著相关性（R₁ = 0.74，P < 0.01），这表明排放动态主要由陆地DIC的输出驱动，而溪流中的过程不太重要。我们的结果表明，目前关于土壤侧向DIC输出到水生通道的预算估计需要修订，因为它们没有考虑源头溪流中的实际情况。对淡水系统侧向溪流碳输出和CO₂排放的任何量化都必须包括源头溪流以及水生通道的下游部分。
