Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes
Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes
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DOI：
10.1002/2016jg003464
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发表时间：
2016-12
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影响因子：
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通讯作者：
L. Vihermaa;S. Waldron;T. Domingues;J. Grace;E. Cosio;Fabián Limonchi;C. Hopkinson;H. Rocha;E. Gloor
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作者：
L. Vihermaa;S. Waldron;T. Domingues;J. Grace;E. Cosio;Fabián Limonchi;C. Hopkinson;H. Rocha;E. Gloor
我们将排水分析与涡动相关（eddy covariance， EC）测量的陆地二氧化碳通量相结合，构建了西亚马逊流域一个集水区的整体碳收支。由于河流碳输出可以代表永久碳输出，因此必须将其纳入整个站点的碳平衡评估中，但很少进行。通量塔的足迹面积由两条小溪流（~ 5-7 km2）排出，我们测量了溶解无机碳（DIC）、溶解有机碳（DOC）、颗粒有机碳（POC）输出和CO2流出。EC测量显示，该地点的碳平衡为+0.7±9.7 Mg C ha−1 yr−1（大气源），河流输出为0.3±0.04 Mg C ha−1 yr−1。在全部河流损失中，DIC占34%，DOC占37%，POC占29%。雨季是河流C输出最重要的季节。EC结果和之前的生物质小区研究存在很大的不确定性（- 0.5±4.1 Mg C / ha - 1 yr - 1）；因此，不能确定该场址是碳汇还是碳源。河流出口仅对应于与站点C平衡相关的不确定性的3-7%；因此，需要考虑其他因素，以减少不确定性和改进估计的C平衡。然而，河流C输出是显著的，特别是在几乎中性的地点，河流损失可能决定地点C平衡的方向。C下游的命运决定了河流输出对气候的总体影响。
We constructed a whole carbon budget for a catchment in the Western Amazon Basin, combining drainage water analyses with eddy covariance (EC) measured terrestrial CO2 fluxes. As fluvial C export can represent permanent C export it must be included in assessments of whole site C balance, but it is rarely done. The footprint area of the flux tower is drained by two small streams (~5–7 km2) from which we measured the dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) export, and CO2 efflux. The EC measurements showed the site C balance to be +0.7 ± 9.7 Mg C ha−1 yr−1 (a source to the atmosphere) and fluvial export was 0.3 ± 0.04 Mg C ha−1 yr−1. Of the total fluvial loss 34% was DIC, 37% DOC, and 29% POC. The wet season was most important for fluvial C export. There was a large uncertainty associated with the EC results and with previous biomass plot studies (−0.5 ± 4.1 Mg C ha−1 yr−1); hence, it cannot be concluded with certainty whether the site is C sink or source. The fluvial export corresponds to only 3–7% of the uncertainty related to the site C balance; thus, other factors need to be considered to reduce the uncertainty and refine the estimated C balance. However, stream C export is significant, especially for almost neutral sites where fluvial loss may determine the direction of the site C balance. The fate of C downstream then dictates the overall climate impact of fluvial export.