Erosion of organic carbon from the Andes and its effects on ecosystem carbon dioxide balance
Erosion of organic carbon from the Andes and its effects on ecosystem carbon dioxide balance
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DOI：
10.1002/2016jg003615
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发表时间：
2017-03-01
影响因子：
3.7
通讯作者：
Malhi, Y.
中科院分区：
文献类型：
--
作者：
Clark, K. E.;Hilton, R. G.;Malhi, Y.
安第斯山脉的多产森林受到高侵蚀率的影响，这些侵蚀率为亚马逊河提供沉积物和来自最近光合作用的生物量和地质来源的碳。尽管认识到这一点，但对安第斯山脉河流中颗粒有机碳（POC）的来源和排放仍然知之甚少。我们在秘鲁科斯尼帕塔河的两个河流监测站收集了1年多的悬浮沉积物。悬浮物的碳同位素（C-14、C-13和C-12）和氮与有机碳比值表明，POC是沉积岩（POCpetro）和陆地生物圈（POCbiosphere）的混合物。大部分POC（生物圈）具有与表层土壤相似的组成，估计其年龄大多小于850 C-14年。2010年的悬沙产沙量为3500 +/- 210 tkm(-2) yr(-1)，是亚马逊流域产沙量的10倍。POCbiosphere产量为12.6 +/- 0.4 t C km(-2) yr(-1)， POCpetro产量为16.1 +/- 1.4 t C km(-2) yr(-1)，主要在汛期（12月至3月）排放。河流的有机生物圈排放量大到足以决定安第斯森林是二氧化碳的来源还是汇。据估计，安第斯山脉的pocepetro的侵蚀排放量比亚马逊盆地下游马德拉河的pocepetro排放量要大得多（约为1Mt C yr(-1)），这表明pocepetro的氧化抵消了硅酸盐风化作用导致的二氧化碳减少。为了充分了解亚马孙河流域的碳收支，需要更好地约束安第斯山脉的pobiosphere和popetro的通量和命运。
Productive forests of the Andes are subject to high erosion rates that supply to the Amazon River sediment and carbon from both recently photosynthesized biomass and geological sources. Despite this recognition, the source and discharge of particulate organic carbon (POC) in Andean Rivers remain poorly constrained. We collected suspended sediments from the Kosnipata River, Peru, over 1 year at two river gauging stations. Carbon isotopes (C-14, C-13, and C-12) and nitrogen to organic carbon ratios of the suspended sediments suggest a mixture of POC from sedimentary rocks (POCpetro) and from the terrestrial biosphere (POCbiosphere). The majority of the POC (biosphere) has a composition similar to surface soil horizons, and we estimate that it is mostly younger than 850 C-14 years. The suspended sediment yield in 2010 was 3500 +/- 210 tkm(-2) yr(-1), >10 times the yield from the Amazon Basin. The POCbiosphere yield was 12.6 +/- 0.4 t C km(-2) yr(-1) and the POCpetro yield was 16.1 +/- 1.4 t C km(-2) yr(-1), mostly discharged in the wet season (December to March) during flood events. The river POCbiosphere discharge is large enough to play a role in determining whether Andean forests are a source or sink of carbon dioxide. The estimated erosional discharge of POCpetro from the Andes is much larger (similar to 1Mt C yr(-1)) than the POCpetro discharge by the Madeira River downstream in the Amazon Basin, suggesting that oxidation of POCpetro counters CO2 drawdown by silicate weathering. The flux and fate of Andean POCbiosphere and POCpetro need to be better constrained to fully understand the carbon budget of the Amazon River basin.