摘要:
湿地生态系统仅占全球陆地面积的3%~6%，但其碳储量占全球陆地碳库的1/3，相当于大气中碳含量的75%。因此，湿地生态系统在全球碳、氮循环和气候变化研究中起着重要作用。然而，作为一种重要的湿地类型，滨海湿地碳累积变化远没有泥炭地研究广泛。本研究的主要目的是评估江苏盐城滨海湿地近现代碳、氮累积速率变化历史，并估算近150年来盐城湿地碳累积通量。利用210Pb放射性测年方法，结合沉积物干容重、碳和氮含量等基本理化参数，计算近现代碳累积速率(RERCA)和近现代氮累积速率(RERNA)，进而估算近150年来碳储存通量。互花米草滩地和光滩沉积柱芯(SAF-1和BAF-1)的平均RERCA分别是165gC∙m−2∙a−1和116gC∙m−2∙a−1，平均RERNA分别是3.99gN∙m−2∙a−1和1.68gN∙m−2∙a−1。近150年来，RERCA和RERNA随着时间不断增加，展现出极强的固碳潜力。盐城湿地过去150年来的碳、氮累积通量被估算为17.4~24.8kgC∙m−2和0.25~0.59 kgN∙m−2。RERCA和RERNA之间有着显著的相关关系。本研究将有助于对滨海湿地碳、氮累积历史和潜力变化的评估，也能增进对在当前气候变化和人类活动双重影响下盐城滨海湿地的相应反馈作用的理解。
Abstract:
Wetland ecosystems account for only 3% - 6% of the world’s land surface, but the carbon (C) stock in these systems accounts for one-third of the global terrestrial C pool, which is equivalent to 75% of the C stock in the atmosphere. Therefore, wetland ecosystems play a key role in the study of global C and nitrogen (N) cycle and climate change. Nevertheless, as an important wetland type, coastal wetlands have been scarcely studied in term of C accumulation compared to the peatlands. The main objective of this study was to evaluate the recent rate of C accumulation (RERCA) and the recent rate of N accumulation (RERNA) in two kinds of coastal wetlands in Yancheng, Jiangsu province, and estimate the inventory of C accumulation over the last 150 years. Using sediment C and N content, dry bulk density, and Pb-210 dating, we determined the accumulation rates of C and N in profiles from Yancheng coastal wetland, from Yancheng coastal wetland, and then we estimated the flux of C storage in the past 150 years. With respective to the Spartinaalterniflora flat (SAF-1) and the bare flat (BAF-1), the RERCA ranged from 116 to 165 gC∙m−2∙a−1, and the RERNA ranged from 1.68 to 3.99 gN∙m−2∙a−1. There was an obvious increasing trend for RERCA and RERNA over the last 150 years, indicating a great potential in C sequestration in the sediments. The historical inventories of C and N were 17.4 - 24.8 kgC∙m−2 and 0.25 - 0.59 kgN∙m−2, respectively. The accumulation rates of C and N were directly related. The results would be helpful in evaluating the C and N accumulation history and sequestration potential in coastal wetland and understanding the feedback effects of the Yancheng coastal wetland under climate change and anthropogenic influence.