Source and age of dissolved and gaseous carbon in a peatland–riparian–stream continuum: a dual isotope (14C and δ13C) analysis
Source and age of dissolved and gaseous carbon in a peatland–riparian–stream continuum: a dual isotope (14C and δ13C) analysis
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DOI：
10.1007/s10533-014-9977-y
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发表时间：
2014-04
期刊：
影响因子：
4
通讯作者：
F. Leith;M. Garnett;K. Dinsmore;M. Billett;Kate V. Heal
中科院分区：
文献类型：
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作者：
F. Leith;M. Garnett;K. Dinsmore;M. Billett;Kate V. Heal
放射性碳同位素越来越多地被用于研究泥炭地释放的碳的年龄和来源。本文采用14 C和δ 13 C联合测量方法，测定了泥炭地-河岸带-河流样带中土壤和土壤分解产物[溶解有机碳（DOC）、CO2和CH 4]的同位素组成，以确定碳库之间的同位素特征和潜在的连通性。2012年在两个时间段进行了采样，以调查不同温度、水文和通量条件下的过程。泥炭地和河岸带土壤有机质的同位素组成存在差异，这是河岸带沉积形成的结果。泥炭地的平均放射性碳年龄为551 ± 133年BP，年龄随深度增加而增加，δ 13 C值与C3植物材料作为主要来源一致。相比之下，河岸带的放射性碳年龄要老得多，为1，055 ± 107年BP，没有显示年龄/深度关系;河岸带的δ 13 C也与C3植物材料一致。除9月份DOC外，土壤分解产物绝大多数> 100%现代，14 C值与前5年固定有机质的来源一致。CO2和CH 4从土壤表面的排放也是现代的。相比之下，CO2和CH 4逃避流表面是旧的（CH 4：310-537年BP，CO2：36年BP到现代），并包含一个更复杂的混合源结合土壤有机质和地质碳。结果表明，相当大的现代碳垂直运输到土壤剖面内的深度。现代最近固定的碳的重要性和河岸和流同位素签名之间的差异表明，泥炭地（而不是河岸带）是最重要的碳源流水。
Radiocarbon isotopes are increasingly being used to investigate the age and source of carbon released from peatlands. Here we use combined14C and δ13C measurements to determine the isotopic composition of soil and soil decomposition products [dissolved organic carbon (DOC), CO2and CH4] in a peatland–riparian–stream transect, to establish the isotopic signature and potential connectivity between carbon pools. Sampling was conducted during two time periods in 2012 to investigate processes under different temperature, hydrological and flux conditions. Isotopic differences existed in the peatland and riparian zone soil organic matter as a result of the riparian depositional formation. The peatland had a mean radiocarbon age of 551 ± 133 years BP, with age increasing with depth, and δ13C values consistent with C3 plant material as the primary source. In contrast the riparian zone had a much older radiocarbon age of 1,055 ± 107 years BP and showed no age/depth relationship; δ13C in the riparian zone was also consistent with C3 plant material. With the exception of DOC in September, soil decomposition products were predominately >100 %modern with14C values consistent with derivation from organic matter fixed in the previous 5 years. Emissions of CO2and CH4from the soil surface were also modern. In contrast, CO2and CH4evaded from the stream surface was older (CH4: 310–537 years BP, CO2: 36 years BP to modern) and contained a more complex mix of sources combining soil organic matter and geogenic carbon. The results suggest considerable vertical transport of modern carbon to depth within the soil profile. The importance of modern recently fixed carbon and the differences between riparian and stream isotopic signatures suggests that the peatland (not the riparian zone) is the most important source of carbon to stream water.