互花米草生物量变化对盐沼沉积物有机碳组分和来源的影响:以王港河口潮滩为例

Impact of Spartina alterniflora biomass variation on content and sources of organic carbon fractions in salt marshes: A case study of tidal salt marsh of Wanggang Estuary, Jiangsu Province

2012-2013年在江苏王港典型互花米草盐沼湿地采集了4根柱状样和48个表层样，通过对比光滩和互花米草滩沉积物中总有机碳（TOC）、活性有机碳（Lc）和顽固性有机碳（Rc）含量，结合互花米草生物量季节变化，探讨了互花米草生物量对沉积物中有机碳组分的影响。结果表明，互花米草滩表层沉积物中LC含量及其中互花米草来源比例，均与互花米草地表枯落物量密切相关，但存在两个月的“相位差”，这与枯落物有机碳快速分解时间一致，说明枯落物通过提高沉积物中LC的含量，提高了TOC含量并改变了TOC组分。互花米草地下生物量主要分布在0～20 cm深度内，该深度范围内互花米草滩各形态碳含量较高，LC和RC含量分别达到了光滩的4．03倍和1．70倍；同时，TOC中LC所占比重在0～20 cnl深度内较高，也表现出先下降后不变的趋势；另外，不同深度各形态有机碳含量均与地下生物量之间存在较好的正相关关系，说明地下生物量是影响沉积物各形态碳含量的重要因素，且对LC的影响大于RC。

In order to investigate the impact of S. alterniflora invasion on soil organic carbon dynamics in north Jiangsu coastal wetlands, four sediment cores were collected at the intertidal flats near the estuary of the Wanggang River in 2012. Surface sediments as well as the biomass of S. alterniflora were gathered bimonthly from October 2012 to June 2013. We analyed the labile and recalcitrant C and N in both coral and surface sediments using soil fraction and stable organic carbon isotopes. Our results show that seasonal variation of labile organic carbon （LC） content is closely related to surface litter mass, but a 2-month phase shift exists between them Meanwhile, the phase-shift phenomenon was also recorded for the proportion of LC orginated from S. alterniflora and surface litter mass. However, the content of RC （recalcitrant organic carbon） was found to be not as significantly correlated to the surface litter mass as that of LC, indicating that litter is a dominant source of LC in surface sediments and the fractions of TOC were changed by incresed LC inputs from S. alterniflora litter. Furthermore, underground biomass displayed an exponential decay curve corresponding to sediment depth, as 60%of the biomass was observed in the top 20 cm layer. On one hand, S. alterniflora invasion can largely increase the contents of both LC and RC when compared with the bare flat, especially within the 0-20 cm depth sediment layer The average LC and RC contents in sediments of the top 20 cm depth layer in S. alterniflora salt marsh, were 170% and 403% that of the sediments in bare flat, respectively, in terms of the quantity 3.27 and 6.75 mg/g, On the other hand, the LC and RC contents of S.alterniflora marsh sediments at depths 〈 20 cm, together with the proportion of LC fraction in TOC, were significantly higher than those in deeper sediment layers （〉20 cm）, and show a decreasing trend from surface to the depth of 20 era. The fractions of organic carbon in coral sediments performed a remarkably positive correlatation to S. alterniflora underground biomass, implying that underground biomass greatly influenced the organic carbon fractions in sediments along the profiles.