Abstract Coastal wetlands can serve as a considerable sink for carbon (C) gases. However, the capacity for wetlands to serve as more permanent C and N sinks over the long term is less clear given the time dependence of sediment deposition, organic matter decomposition, and anthropogenic land use change. In this study, we compare the short-term (decadal scale) and long-term (millennial scale) C and N accumulation rates estimated using 137Cs and radiocarbon dating of vibracores collected from a freshwater coastal wetland in the Louisiana Mississippi River deltaic plain (Atchafalaya River delta). The mean short-term (60 yrs) sediment accumulation rate was 1.4 cm/yr while the mean rate of long-term (100–1000 yrs) sediment accumulation was an order of magnitude lower at 0.12 cm/yr. Annual rates of C and N accumulated over the past several thousand years were approximately 10% of that over the past 60 years after correcting for bulk density. These results are similar to other coastal wetlands and suggest that time scale must be considered in determining the relative permanence of C and N storage in coastal wetland soils. This difference is especially important for assessing the role of C cycling in relation to global change models and N cycling related to water quality in accurately quantifying the role of coastal deltaic fresh water wetlands in regulating these biogeochemical cycles.

中文翻译：

---

沿海河流三角洲湿地长期与短期碳和氮固存的差异：对全球预算的影响

摘要 沿海湿地可以作为碳 (C) 气体的重要汇。然而，考虑到沉积物沉积、有机物分解和人为土地利用变化的时间依赖性，湿地长期作为更永久的 C 和 N 汇的能力不太清楚。在这项研究中，我们比较了使用从路易斯安那州密西西比河三角洲平原 (Atchafalaya) 淡水沿海湿地收集的颤振石的 137C 和放射性碳测年估算的短期（十年尺度）和长期（千年尺度）C 和 N 积累率河三角洲）。平均短期（60 年）沉积物积累速率为 1.4 厘米/年，而长期（100-1000 年）沉积物积累的平均速率低一个数量级，为 0.12 厘米/年。过去几千年累积的 C 和 N 年率在校正容重后约为过去 60 年的 10%。这些结果与其他沿海湿地相似，表明在确定沿海湿地土壤中碳和氮储存的相对持久性时必须考虑时间尺度。这种差异对于评估与全球变化模型相关的碳循环和与水质相关的氮循环在准确量化沿海三角洲淡水湿地在调节这些生物地球化学循环中的作用方面尤为重要。这些结果与其他沿海湿地相似，表明在确定沿海湿地土壤中碳和氮储存的相对持久性时必须考虑时间尺度。这种差异对于评估与全球变化模型相关的碳循环和与水质相关的氮循环在准确量化沿海三角洲淡水湿地在调节这些生物地球化学循环中的作用方面尤为重要。这些结果与其他沿海湿地相似，表明在确定沿海湿地土壤中碳和氮储存的相对持久性时必须考虑时间尺度。这种差异对于评估与全球变化模型相关的碳循环和与水质相关的氮循环在准确量化沿海三角洲淡水湿地在调节这些生物地球化学循环中的作用方面尤为重要。