【作者】 杨靓青；

【导师】 贺宝根； 温家洪；

【作者基本信息】 上海师范大学 ， 自然地理学， 2009， 硕士

【摘要】 湿地生态系统碳循环在全球碳循环中起着重要的作用,并对全球气候变化有着巨大的影响。长江口潮滩面向开阔海域,受潮汐作用、波浪作用等特殊水动力因子影响深刻,且淤涨迅速,这些独特的条件使得长江口潮滩盐沼地区中有机碳的浓度、通量等特征有别于世界其它河口盐沼湿地。因此,盐沼地区有机碳的动力输移与通量研究在湿地生态系统碳循环中起着关键性作用,也是全球碳循环研究在海岸带比较薄弱的一环。正确认识盐沼地区和特殊动力条件(潮汐、波浪)下有机碳的浓度和通量变化,对于揭示目前尚不清楚的海岸带碳循环研究在全球碳循环中的重要性有着重要的意义。以长江口崇明东滩的高潮滩盐沼为主要研究区域,研究盐沼地区有机碳短期内的动力输移与通量变化。揭示潮周期内有机碳的浓度变化,计算潮周期内有机碳通量的结果,并分析影响有机碳短期变化的因子,以期揭示潮滩湿地碳的排放通量变化,得出主要结论如下:1.夏季(7、8月)草滩平均有机碳浓度为18.2 mg g -1,光滩平均有机碳浓度为10.8 mg g -1。潮周期内草滩有机碳浓度是光滩的1.7倍,夏季(7、8月)草滩有机碳浓度约为春季的1. 5倍。沉积物有机碳浓度变化总体趋势较为平稳,平均有机碳浓度为1.6 mg g -1。沉积物有机碳浓度呈现草滩内部>草滩边缘>光滩的变化趋势。2.潮周期内春夏两季草滩和光滩地区悬浮物有机碳浓度变化大致分为两种:涨潮初期、落潮中后期分别出现峰值,有机碳浓度变化较大;全潮只在落潮的中后期出现一次峰值,有机碳浓度呈现出涨潮初期逐渐上升,落潮中后期出现震荡的趋势。3.盐沼地区有机碳总通量值变化范围在1676 g/m~15114 g/m之间,有机碳净通量多为正值,该测点的有机碳通量呈现稳定向岸输移积累。光滩地区(测点BF)有机碳总通量值变化范围在1787 g/m~50391 g/m之间,有机碳向岸和离岸输移交替变化频繁,但光滩测点有机碳总体以累积为主。两测点的有机碳输移率fPOCx的过程线形状均如同正弦曲线,均表现为涨潮初期向岸输移、涨落潮后期离岸输移的变化规律,且向岸有机碳输移率均明显大于离岸的。4.平静天气条件下潮汐作用的大小控制着盐沼和光滩有机碳输移水平和输移量。平静天气条件下最大水深(hmax)与各断面有机碳总通量(FPOCx)之间有显著正相关的幂函数关系,各潮次有机碳总通量与最大水深的三次方呈显著正相关,相关系数为0.94。所测潮次最大水深与潮次平均流速之间有显著线性正相关,相关系数为0.74。实测潮次的有机碳浓度与最大水深之间也存在显著线性正相关,相关系数为0.61。5.通过机制分解法得出盐沼测点所实测的三个潮次中,平流输移对有机碳输移的贡献率在45﹪~81﹪之间;潮泵输移作用对有机碳输移的贡献率在18﹪~54﹪之间。光滩测点所实测的四个潮次中,平流输移对有机碳输移的贡献率在22﹪~61﹪之间;潮泵输移作用对有机碳输移的贡献率在38﹪~77﹪之间。平流输移(T1 + T2)和潮泵输移(T3 + T4 + T5)是对长江口有机碳输移影响最大的动力因素。更多还原

【Abstract】 Carbon cycle in marsh areas is playing an important role in global carbon cycle. The tidal flat of Yangtze Estuary is facing the open sea, and is influenced by profound special hydrodynamic factors such as tidal effect, wave effect and rapid silting, which make organic carbon concentration, flux and other characteristics different from those in other estuarine marsh areas of the world. Therefore, the study of dynamic transport and flux of organic carbon in salt marsh areas is the key role in ecosystem of salt marsh areas, which is also a neglecting part of global carbon cycle research in coastal zone. The correct understanding of organic carbon concentration changes and flux changes under special dynamic forces like tides and waves in salt marsh areas is meaningful in unveiling the vital significance of costal carbon cycle in global carbon cycle.This article took the upsurge beach salt marsh marginal zone of Chongming Dongtan along Yangtze River as the main study area. The main purposes of this article were to study the short-term organic carbon dynamic transport and flux changes in salt marsh areas, to reveal the changes of short-term organic carbon concentration, to calculate organic carbon flux in every single tidal cycle and to analysis the impact factors to the short-term organic carbon, thus, unveiling the organic carbon flux changes in tidal flats. The main conclusions could be listed as follows.1. The average value of organic carbon concentration in salt marsh area was 18.2 mg g -1, and the average value of organic carbon concentration in bald field was 10.8 mg g -1. The average organic carbon concentration value in salt marsh area during neap and spring tidal cycles was 1.7 times as that of bald field. The average organic carbon concentration value in summer was 1.5 times than that in spring in salt marsh area. The sediment organic carbon concentration in spring showed a steady trend with an average value of 1.6 mg g -1. The sediment organic carbon concentration value in internal salt marsh was higher than that of marsh edge, which was higher than that of bald field.2. The basic rule of tidal-cycle sediment organic carbon concentration changes in suspended sediments in spring and summer seasons could be roughly divided into two types. Peak value occurred during young flood and latter half ebb flood respectively with fairly large changes in organic carbon concentration during the whole tide. Only one peak value occurred in the latter half ebb flood during the whole tide. In this type, organic carbon concentration showed a gradual increase in the young flood and concussion of increasing and decreasing in latter half ebb flood.3. The range of total organic carbon flux values in salt marsh area were between 1676 g/m and 15114 g/m. Most net carbon flux values in salt marsh area were positive, indicating organic carbon flux in salt marsh area was in a stable state of onshore accumulation. The range of total organic carbon flux values in bald field were between 1787 g/m and 50391 g/m. Frequent onshore and offshore alternating changes were obvious in bald field, but organic carbon flux in bald field was accumulating onshore overall. The process line of organic carbon transportation rate ( fPOCx) in these two measuring points were both shaped sine curves, which presented onshore transportation in high tides and offshore transportation in ebb tides. Onshore transport was dominant.4. Under calm weather conditions, tidal effects mainly controlled the organic carbon transport capacity and quantity in both bald field and salt marsh measuring points. Under calm weather conditions, there was significant positive correlation of power function between the maximum water depth (hmax) and total organic carbon flux (FPOCx) in each cross-section, with coefficient of 0.94. There was remarkable linear positive correlation between the maximum water depth and the mean water velocity, and between particle organic carbon concentration and the maximum water depth, with coefficient of 0.74 and 0.61 respectively.5. By means of mechanism analyses method, during the three tides experimented in salt marsh area, the contribution rate of advective sediment flux was between 45﹪and 81﹪.The contribution rate of tidal pumping effect was between 18﹪and 54﹪. During the four tides experimented in bald field, the contribution rate of advective sediment flux was between 22﹪and 61﹪.The contribution rate of tidal pumping effect was between 38﹪and 77﹪.Advective sediment flux and tidal pumping effect were the most important items to the total organic carbon discharge.更多还原