【作者】 曹磊；

【导师】 宋金明；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋化学， 2014， 博士

【摘要】 滨海湿地是地球碳循环的一个重要源汇地，揭示滨海湿地碳储存、收支等关键过程对探明全球碳循环意义重大。本文聚焦对比研究了山东北部广饶潮汐湿地和昌邑柽柳林湿地两种典型滨海湿地沉积物中碳的生物地球化学特征，诠释了滨海湿地沉积物中的不同形态活性有机碳库和难降解有机碳库状况，在此基础上，评估了两种滨海湿地沉积物中稳定有机碳库的储量以及沉积物有机碳库的稳定性，这可为深入研究我国滨海湿地碳的生物地球化学循环及准确评估滨海湿地碳埋藏能力提供基础。论文研究获得的主要结论如下：1.山东半岛北部广饶潮汐湿地和昌邑柽柳林湿地沉积物中碳的含量变化特征、来源、控制因素有较明显的差异，植被和潮沟对沉积物有机碳和无机碳的持留有重要影响。广饶潮汐湿地沉积物中无机碳的垂直变化较小，但浓度较高，有机碳变化相对较大，与芦苇、碱蓬优势群落的根系发育有关，定期的淹水使沉积物常处于厌氧环境，导致有机质矿化分解速率较低，其结果使有机碳得到更多的保存；昌邑柽柳林湿地无机碳的浓度较低，而其有机碳主要来源于覆盖植被地上生物量和地下生物量的输入，但这种输入的影响仅在0-20cm沉积层内发挥作用，其下层根系的地下生产力较低，且有机碳矿化速率较快。广饶潮汐湿地GRB1柱样沉积物总有机碳含量在剖面32cm以上随深度增加缓慢上升，此后则表现为下降趋势。GRC2站位TOC含量在垂直剖面的变化趋势并不是很规则，在前10cm随着深度的增加而逐渐降低，之后除在12-14cm和38-40cm两个深度出现明显的积累峰以外，TOC均表现为随深度增加而上升的趋势。GRB1与GRC2柱样平均含量分别为1.798g/kg和3.109g/kg，变异系数为16.15%和19.10%。GRC2站位的芦苇相较于GRB1站位的碱蓬具有更高的生物量，同时芦苇通过强壮的根系来影响着更深层的土壤有机碳的积累，而碱蓬的根系并不发达，不能够通过深入土壤来达到有机碳的显著积累。因此，GRB1柱样中TOC含量和变异系数均低于GRC2。GRB1和GRC2无机碳含量的均值分别为11.25g/kg和10.93g/kg，总体上广饶湿地沉积物中无机碳的垂直变异较小。对于昌邑柽柳林湿地，潮水无法抵达防潮大坝内侧的研究站位，其TOC含量的垂直分布特征基本上呈现表层聚积的特点，在前10cm随深度增加剧烈下降，而在20cm以下变化幅度较小。原因在于研究区域土壤表层枯落物丰富，因此表层有机碳含量较高，其次研究区域植物根系较浅，根系分布由表层向深层递减。昌邑湿地沉积物中无机碳含量较低，沉积物无机碳含量最高的CYA9站位平均值仅为4.39g/kg。受地理及环境因素的综合影响，昌邑柽柳林湿地碳的埋藏能力有很大提升空间。2.首次研究揭示了滨海湿地沉积物不同形态活性有机碳（水提和酸提部分）的变化特征。热水可提取碳（HWC）的含量远高于可溶性有机碳（冷水提取）的含量，昌邑湿地沉积物中HWC含量比广饶湿地低，但所占总有机碳的比例较广饶湿地高，潮汐、植被与地貌等对HWC有重要影响；盐酸提有机碳含量在不同类型湿地的柱样沉积物中变化较大，环境指示意义不明确，但不同浓度硫酸提取活性有机碳在指示沉积物有机碳降解程度方面，很有潜在价值。两类滨海湿地沉积物中可溶性有机碳含量差别很大，广饶湿地沉积物中DOC含量远高于昌邑湿地。GRB1和GRC2柱样中DOC含量均值分别为637.37mg/kg和712.705mg/kg，后者DOC含量波动较前者显著。在昌邑湿地，CYA3柱样中DOC最高值74.68mg/kg出现在表层0-2cm，在浅层深度DOC大致呈随深度增加而下降的趋势。沉积物含水量影响着DOC在总有机碳中的分配，两类型湿地沉积物中DOC占总有机碳比例差别很大。广饶湿地沉积物中DOC占总有机碳含量比例的均值在34.86%-24.08%之间，而昌邑柱样则仅在2.42%-1.54%之间。GRC2柱样中HWC含量高于GRB1，均值为0.751g/kg，而在昌邑湿地，CYA9柱样中HWC含量的平均值高于CYA3。CYA3柱样沉积物中HWC含量与总有机碳含量是显著相关的，其垂直变异最小，而其它站位HWC的变异系数则很接近。研究显示，潮汐涨落对滨海湿地沉积物中热水可提取碳的分布产生了不可忽视的影响，在不同的植被与地貌等条件的综合影响下HWC产生了较强的空间异质性。GRC2柱样沉积物中盐酸酸提有机碳含量显著高于GRB1柱样。昌邑湿地CYA3柱样的酸提有机碳含量总体来说呈下降趋势，均值为0.92g/kg。而在CYA9站位，沉积物中酸解有机碳含量变化很小，仅在0-12cm内的浅层有一定幅度的波动。不同浓度的硫酸将沉积物中的活性有机质分解为两组水解产物，不同组分的含量与分布在一定程度上可以指示沉积物中有机碳的降解程度。不同湿地沉积更加稳定。在广饶湿地，GRC2站位芦苇的生长与根系的深入向沉积物中输入较多的活性有机质，使GRC2柱样沉积物中组分I与组分II的含量高于GRB1。GRB1柱样中组分I与组分II的含量均值分别为0.583g/kg和0.290g/kg，而GRC2柱样沉积物则分别为0.860g/kg和0.409g/kg。昌邑湿地CYA3柱样中，组分I含量在前10cm剧烈下降，均值为0.639g/kg。组分II的含量在前16cm是随着深度增加逐渐降低的，之后深度内的波动一直较小。3.获取了不同类型滨海湿地沉积物中难降解有机碳的含量及垂直分布特征，分析了沉积物中有机碳难降解指数，阐明了不同类型滨海湿地沉积物中的稳定有机碳库特征。作为滨海湿地碳最终汇地的沉积物，其难降解有机碳含量在广饶湿地显著高于昌邑柽柳林湿地。有机碳难降解指数结果表明，广饶湿地沉积物有机碳库的稳定性高于昌邑湿地，广饶湿地有机碳稳定性变化不大，潮汐在维持其湿地有机碳的稳定性方面起到了非常重要的作用。昌邑湿地沉积物有机碳难降解指数较低且变化大，有机质相对易矿化分解；估算1m沉积层内，广饶湿地沉积物稳定有机碳库平均为21.9kg/m2，昌邑湿地仅为7.5kg/m2，表明昌邑湿地的碳封存具有更高的提升潜力。广饶湿地GRB1和GRC2沉积物中难降解有机碳的平均含量分别0.919g/kg和1.671g/kg，造成这种差异的原因可能是不同植被的有机质的输入质量在沉积物剖面内有着显著差异。GRB1沉积物中难降解有机碳随着深度呈现先升高后降低的趋势，GRC2则呈现出先降低后增加的趋势。昌邑柽柳林湿地沉积物中难降解有机碳含量较低。CYA3柱样中难降解有机碳含量随深度的分布模式为先剧烈降低后波动幅度减小，而CYA9柱样难降解有机碳约为0.384g/kg，变化幅度较小。由于植被枯落物在表层的累积较多，而活性有机质在浅层内的淋溶过程使得下层的积累不断增加，CYA3站位有机碳的稳定性在浅层是随深度增加而降低的。在潮汐湿地沉积物中有机碳库稳定性较高，而对于昌邑湿地，其在1m深度内的稳定有机碳储量非常低。估算得到1m深度内GRB1，GRC2和CYA3，CYA9站位沉积物中稳定有机碳库的储量分别为15.074kg/m2，28.748kg/m2，9.371kg/m2和5.652kg/m2。光滩CYA9站位虽无植被生长，然而其稳定有机碳剖面分布较为均匀，在1m深度内可达到CYA3储量的一半以上。更多还原

【Abstract】 Coastal wetlands are located at a critical interface between the terrestrial andmarine environments, which are generally known to be biogeochemical reactors formaterial sinks, sources, and transformations in landscapes. Coastal wetland plays animportant role in the global carbon budget. The research of soil carbon deposition andburial is of great significance for clearly understanding global carbon cycle. Thisstudy investigated the vertical variations of carbon pool and their influencing factorsin different coastal wetland through the comparison of the biogeochemicalcharacteristics of carbon in sediments from two typical coastal wetlands of Shandongpeninsula, and characterized the labile carbon pool and recalcitrant carbon pool in thecoastal wetlands，then estimated the storage of stabile carbon pool and discussedstability of the sediment organic carbon pool. Our study would be helpful for futureresearch on the carbon biogeochemical cycle and accurate assessment of carbon burialability for the coastal wetlands. Major results and conclusions are as the following:1. Biogeochemical characteristics of carbon in sediments from different coastalwetlands were quite different, while vegetation and tidal creek had greatinfluence on sediments organic carbon and inorganic carbon retention. Generally,the inorganic carbon contents in Guangrao wetland were homogeneous and quitehigh, while the variation of organic carbon was obvious. It could be explained bythe point that the capacity of wetland soils for organic matters retention andplant litters input amounts were very distinct within this wetland, and themineralization and decomposition of organic matter were quite slow under thelong-term anaerobic situation. Inorganic carbon contents in Changyi wetlandsediments were lower, and the profile distributions of TOC might be dominantlycontrolled by the aboveground and belowground biomass of local vegetation. Soilorganic carbon mineralization rates were higher in Changyi wetland, and thecarbon burial capacity still needed to be improved.In Guangrao wetland, the TOC contents in GRB1slightly increased in the profileuntil a depth of30-32cm firstly, and then it showed a decreased trend with depth with the lowest value of1.139mg g-1at72-74cm. TOC contents in GRC2profile werehigher than that in GRB1. An irregular increase of TOC contents was observed alongGRC2profile. In the upper10cm, SOC contents gradually decreased with depth, thenit showed a gradually increase trend except for two obvious accumulation peaks at the12-14cm and38-40cm depth. Firstly, the GRC2area had a tidal creek nearby, whichcan bring much allochthonous nutrients deposited. Secondly, GRC2surface wascovered with P.australis, which had much higher biomass and sufficiently strongerroots than GRA2with S.salsa. Generally, the inorganic carbon contents in Guangraowetland were homogeneous, the average of the inorganic carbon contents in GRB1and GRC2were11.25g/kg and10.93g/kg, respectively. In Changyi wetland, TOCcontents at most study sites that located at supralittoral zone showed a regularlychange pattern that generally decreased with depth along about an upper10cm depthprofile and then fluctuated within a limited range. There was only occasionally floodfrequency when spring tide or storm surge came. Therefore, the profile distributionsof TOC might be dominantly controlled by the aboveground and belowgroundbiomass of local vegetation. Compared to Guangrao wetland, inorganic carboncontents in Changyi wetland sediments were lower.2. Dissolved organic carbon (DOC), hot water extractable carbon (HWC) andacid hydrolyzable carbon distribution characteristics in different coastalwetlands were obtained, and the HWC content was quite higher than DOCcontent. While the HWC content in Changyi wetland were lower than that inGuangrao wetland, its proportion in total organic carbon was higher. Tidal,vegetation and landscape were of significance for the distribution of HWC.Hydrochloric acid extraction of organic carbon content varied differently, and itsenvironmental significance was not clear. However, different concentrationsulfuric acid could divided the labile organic matter into two groups ofhydrolysate extraction that had great potential value for indicating the organiccarbon degradation.Dissolved organic carbon content in different coastal wetlands varied greatly, with higher contents in the sediments of Guangrao wetland. The average contents ofDOC in GRB1and GRC2were637.37mg/kg and712.705mg/kg, respectively, andthe variation of DOC content in GRC2was more significantly than GRB1. In ChangyiWetland, the maximum value of74.68mg/kg appeared in the surface0-2cm, andDOC in the shallow depth decreased. Water content affected the allocation of DOC inthe TOC, and the proportion of DOC in TOC in different wetlands was of greatdifference. The proportion of DOC in the GRB1and GRC2profiles were34.86%and24.08%, while the CYA3and CYA9profiles were only2.42%and1.54%. While theHWC content in Changyi wetland sediment were lower than that in Guangrao wetland,its proportion in total organic carbon was higher. The mean content of HWC in GRB1was0.632g/kg, and it was higher in GRC2with an average value of0.751g/kg. InChangyi wetland, the average HWC content in CYA9was higher than that of CYA3.The vertical variation of HWC content in CYA3which was not influenced by tide isthe smallest, while the variation coefficients in the other three stations were quitesimilar. In addition, only in CYA3the content of HWC was significantly related to thetotal organic carbon. These results implied that tidal fluctuations could bringconsiderable impact on the HWC in the sediments of the coastal wetlands, and thecomprehensive effects of different vegetation and landform conditions caused thestrong spatial heterogeneity of HWC distribution. Hydrochloric acid extraction oforganic carbon content in GRC2was significantly higher than that of GRB1. The acidhydrolyzable carbon in GRB1was within the range of0.527g/kg-1.280g/kg, whilethe GRC2was in the range of1.087-2.309g/kg. In Changyi wetland, the verticalvariation of acid hydrolyzable carbon in CYA3showed obvious downward trend withthe average of0.92g/kg. In CYA9, the variation of acid hydrolyzable carbon was verysmall, and it only had a certain degree of volatility within the0-12cm shallow layer.Different concentration sulfuric acid could divide the labile organic matter into twogroups. In different wetland, labile pool II were significantly lower than labile pool I,and changes of pool II were more stable with depth than pool I. In Guangrao wetland,the mean content of GRB1pool I and pool II were0.583g/kg and0.290g/kg, whilethat of the GRC2were0.860g/kg and0.409g/kg, respectively. In Changyi wetland, pool I sharply decreased within the first10cm along CYA3profile. Pool II increasedwith the depth within the first16cm, after which the fluctuations became smaller.3. The recalcitrancy indices of sediment organic carbon were analyzed, andvertical distribution characteristics of recalcitrant carbon pool in differentcoastal wetlands were illuminated. Generally, stability of organic carbon pool inGuangrao wetland sediments was higher than that of Changyi wetland. InGuangrao wetland, the stability of organic carbon of two sediment profiles werevery close to each other, and the tidal played very important role in maintainingthe stability of sediments organic carbon pool. However, due to environmentalconstraints, the recalcitrancy indices were quite low, and the organic matter inChangyi wetland were easily decomposed. We estimated the stabile carbonstorage capacity of Guangrao and Changyi wetland within1m depth were21.9kg/m2and7.5kg/m2, respectively. The results indicated that the carbonsequestration ability of Changyi wetland had higher potential for improvement.In Guangrao wetland, recalcitrant carbon contents in GRB1and GRC2were0.919g/kg and1.671g/kg, respectively, and this may due to the significantly differentquality of organic matter input in profiles from different vegetation. The recalcitrantcarbon increased with depth firstly and then decreased in GRB1, while it decreasedfirstly and then increased in GRC2. Recalcitrant carbon content was lower in Changyiwetland sediments. The distribution pattern of recalcitrant carbon contents in CYA3showed a dramatic reduction with depth firstly and a slight fluctuation then. Theaverage content of recalcitrant carbon in CYA9was0.384g/kg, with smaller change.In the shallow layer, the stability of organic carbon in CYA3was decreased withdepth, this probably due to more vegetation litter accumulated in the surface layer,besides, the leaching process of the active organic matter in the shallow layer causingthe increasing accumulation. We estimated the stabile carbon storage capacity ofGRB1, GRC2and CYA3, CYA9within1m depth were15.074kg/m2,28.748kg/m2,9.371kg/m2and5.652kg/m2. In tidal wetland, the sediment organic carbon storagestability was relatively high, while the Changyi wetland, due to environmental constraints, the stable organic carbon storage was very low. CYA9was located at thebare tidal flat, however, its stable organic carbon distribution was more uniform, andit can reach more than half of CYA3stable carbon reserves within1m depth.更多还原