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Alternative TitleLong-term carbon accumulation rates and the development and dynamics of a permafrost polygon peatland: shifts between dry and wet conditions
Thesis Advisor王根绪
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Keyword碳累积 低矮灌木 冰楔多边形泥炭沼泽地 西伯利亚东北部 多边形泥炭沼泽动态 古植被重建 微地貌 古气温 苔原
Abstract多边形冰楔泥炭沼泽地在多年冻土土壤中蕴藏着丰富的碳。然而,在植被,温度等作用下长时间梯度(上千年)的碳累积研究较少。本论文通过在俄罗斯西伯利亚东北部的单一多边形泥炭沼泽地选取四个泥炭剖面的样方,在实验室制备连续的0.5cm切片。基于AMS 14C 测年的孢粉密度曲线提供的每个样品切片的时间跨度值,结合碳体积含量,重新测定百年以及千年时间尺度上的碳累计值。以详细的小化石和大化石的分析重建代表干燥古台地的植被和湿润洼地的植被。 在查阅相关领域的国内外文献,全面了解国内外相关研究现状和发展趋势的基础上,通过高分辨率古生态学的垂直剖面泥炭分析,结合14C年代测定,对每0.5cm的切片进行定年;利用孢粉重量浓度的变化、百分含量及通量图谱,计算碳累积数值;采用邻近地区最近几十年气象站的仪器记录,以及北极地区温度曲线,确定多边形泥炭沼泽地的地形、植被、温度与碳累积的相互关系,取得以下主要成果: (1)孢粉分析结果表明植被类型与多边形泥炭地微地貌有着密切的关联。苔属植物、委陵菜属和转板藻都出现在地势较低的区域且数量丰富;桦木属、柳属、泥炭藓属、欧石楠目和草的花粉和孢子主要位于地势较高的区域。 (2)多边形泥炭沼泽是植被、冰、泥炭和水共同作用下的四大要素综合作用而产生的结果。 (3)在过去一千年中,泥炭湿地干湿环境交替变化。植被和泥炭作为中介物,其组合揭示了相对温暖与干燥的台地(或凸起区域)和相对寒冷潮湿的中部低洼区域的环境和碳累积差异性。四个泥炭剖面的长期平均碳累积值为10.6 ± 5.5 g C m-2 yr-1,且碳累积均值在湿润洼地和干燥台地之间没有显著差异(分别为10.6 ± 5.2 g C m-2 yr-1 和10.3 ± 5.7 g C m-2 yr-1)。 (4)尽管观测到增加的碳累积值与温暖气温变化有关,但也发现相反的变化,实际上最高值的碳累积出现在小冰期时期。发现碳累积由多边形湿地内部冰、水、地形与植被等因素间强烈的反馈机制制约,并在千年尺度上大致保持稳定。认为近期的气候温暖以及灌木的扩张并不影响长期碳埋藏率。 总之,本论文通过多边形泥炭沼泽分布,多边形发展、动态及其演变;基于植被、花粉和非花粉孢粉型干湿交替下的古植被重建,以及多边形泥炭沼泽地近1250年碳累积速率的研究,得出多边形泥炭沼泽地地形、植被、温度与碳累积的相互关系;揭示千年尺度上北极典型泥炭湿地的碳累积动态,为北极多年冻土区响应气候变化的碳源汇变化提供科学依据。
Other AbstractIce-wedge polygon peatlands contain a substantial part of the carbon stored in permafrost soils. However, little is known about their long term carbon accumulation rates (CAR) in relation to shifts in vegetation and climate.We collected four peat profiles from one single polygon in NE Yakutia and cut them into contiguous 0.5 cm slices. Pollen density interpolation between AMS 14C dated levels provided the time span contained in each of the sample slices, which – in combination with the volumetric carbon content – allowed for the reconstruction of CAR over decadal and centennial timescales. Vegetation representing dry palaeo-ridges and wet depressions was reconstructed with detailed micro- and macrofossil analysis. Based on the consulting of domestic and foreign literature in relevant field, as well as the full understanding of domestic and foreign relevant research status and development trend, dating is conducted for each 0.5cm section through the vertical section peat analysis of high-resolution paleoecology and 14C age determination. The carbon accumulation is calculated by making use of the changes of sporopollen concentration, percentage composition and flux mapping. The relation between the terrain of the polygon mire, vegetation, temperature, and carbon accumulation is determined according to the instrument record of the meteorological station in recent dozens of years, and the temperature curve in arctic region. The following achievements are obtained. (1) The sporopollen analysis shows that the vegetation form is in close relation with the micro-topography of polygon mire. The carex, potentilla chinensis and mougeotia may occur in low-terrain regions in a large scale. The betula, salix, sphagnum, ericales, and pollen and spore of the grass are mainly in the high-terrain regions. (2) The polygon mire is the result of four combined elements under the combined action of vegetation, ice, peat and water. (3) In the past one thousand years, the dry and wet environment of the mire changes alternatively. The combination of the vegetation and peat, which are the mediators, reveals the difference in carbon accumulation in the warm and dry ridges (or raised regions) and cold and wet depression regions in the middle. The long-term mean carbon accumulation of the four peat sections is 10.6 ± 5.5 g C m-2 yr-1, and there is no difference in the wet depression and dry ridge (namely 10.6 ± 5.2 g C m-2 yr-1 and 10.3 ± 5.7 g C m-2 yr-1 respectively). (4) Although it has been observed that the increasing carbon accumulation is related to the warm temperature, opposite changes are also found out, and the highest carbon accumulation actually occurred in the Little Ice Age. It is found out that the carbon accumulation is restrained by the strong feedback mechanism of such elements as the ice, water, terrain, vegetation, etc. of the polygon wetland, and it kept stable in nearly a thousand years. It is considered that recent warm climate and expansion of shrubs may not impact the long-term carbon bury rate. In conclusion, this thesis through distribution, diversity, development and dynamics of polygon mires, vegetation patterns, recent pollen deposition and distribution of non-pollen palynomorphs in a polygon mire near Chokurdakh, carbon accumulation rates in the last 1250 years of a permafrost polygon peatland. Aims to reveal carbon accumulation dynamics in typical arctic peatland mires, and to provide a scientific basis for carbon source changes in response to climate change.
Document Type学位论文
Recommended Citation
GB/T 7714
高洋. 多年冻土区多边形泥炭沼泽地干湿交替下的碳累积及其演变[D]. 北京. 中国科学院大学,2015.
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