黄河口湿地有机碳来源及其对碳埋藏提升策略的启示

滨海湿地是地球上具有多种独特功能的生态系统,是地球上重要的碳库之一,其在全球碳循环中的作用在近年来越来越受到人们的重视。总结了用C/N、稳定碳同位素和生物标志物等方法追踪黄河口湿地有机碳来源的研究成果,并据此探讨了黄河口湿地的固碳提升策略。黄河口湿地是我国典型的滨海湿地,碳来源复杂,但各种示踪方法均表明有机碳的来源中陆源输入较海源输入优势明显,而且陆源输入以地表径流和植被为主,但海源输入从内陆向近海逐渐增强,碳的来源有明显的时空变化并且受到人类活动的强烈干扰。从有机质来源看,提升黄河口湿地的碳埋藏能力应该从合理调配河流淡水资源、保护植被、加快植物群落演替等方面入手。目前有机碳来源的研究还存在覆盖区域有限、碳源区分粗略、影响因子研究较少等问题,缺乏系统性,多限于观测,对机制的理解十分薄弱,因此难以对碳埋藏能力的提升提供定量化的指导。今后的研究要从以下几个方面加强:1)不同区域和不同环境条件之间的比较研究;2)探寻更具特异性的生物指标、优化数据模型,使来源区分更细致;3)不同来源有机质在沉积物中埋藏效率的对比研究;4)构建湿地碳埋藏能力评估体系,综合考虑各方面因素研发和集成能够最大限度提高滨海湿地碳埋藏能力的技术。

Sources of organic carbon in the wetlands of the Yellow River estuary and instructions on carbon burial promotion strategies

Coastal wetland ecosystem, which has many kinds of special ecological functions, is one of the most important carbon pools on the earth. In recent years, the global climate change caused by the emission of greenhouse gases has increasingly been attented. As a significant carbon sink, the coastal wetland regions play an important role in the global carbon cycle. However, the carbon cycling processes in the coastal wetland are very complicated due to the interactions between land and ocean. Recent research demonstrates that the carbon input is the most important among all the complicated processes as the base of the carbon cycle. The Yellow River estuary wetland is a typical coastal wetland in the Northern China. The organic carbon sources were discussed and the strategies about increasing carbon burial capacity of the wetlands ecosystem were raised in this paper. The sources of organic carbon in the Yellow River estuary wetland were deduced by C/N, stable carbon isotopic compositions and biomarkers.The study showed that the organic carbon sources in the Yellow River estuary wetlands were complex with both terrestrial and marine materials. The C/N, stable carbon isotopic compositions of organic matters and biomarkers distributions showed that the terrestrial input of organic matters to the sediments was more than the marine input. The proportion of marine organic matters increased gradually from inland to coastal areas and from shallow beaches to deeper areas with the enhancing impact of tidal. The organic carbon sources had a significantly seasonal change with primary productivities, runoff of the Yellow River and were disturbed intensively by human activities. On the results of organic carbon sources research, many ways can be used to increase the carbon burial capacity of the Yellow River estuary wetlands such as allocating riverine fresh water input reasonably, protecting vegetation around the estuary and accelerating the succession of plant communities covering the wetlands. The conclusions we drew from the Yellow River Estuary wetland can be extended to other coastal wentlands, especially large estuarine wetlands, because the fundamental principles that drive the biogeochemical processes of the coastal wetlands are basically the same despite the different environmental conditions. The current researches on organic carbon sources of coastal wetland should be improved by extending the study areas, exploring stricter distinguish of carbon sources and systematicly analyzing the influencing factors. Since most researches are non-systematic and merely based on the direct observation rather than the exploration of principles and mechanisms, it is hard to get more quantitative results and effective instructions to the increase of the carbon burial capacity of coastal wetland. Future researches should be enhanced in the following parts: 1) Carrying out more comparative studies of wetlands with different environmental conditions; 2) Searching more specific biological indicators and optimizing date analysis models to make finer distinction of carbon sources; 3) Studying the burial efficiencies of organic matters from different sources; 4) Building the assessment system of carbon burial capacity of wetland, developing and integrating the techniques which can increase the carbon burial capacity of coastal wetlands the most.