沼泽地表水位反演长白山区全新世大暖期以来的气候变化

Typical mires from low to high altitudes in the Changbai Mountains, northeast China have been chosen on the basis of previous work on the peatlands in this area. A transfer function will be established based on the relationship of modern mires plants and water tables in the 50-100 plots under the different habitats along water table gradient in the typical mires. Peat samples will be taken from the profiles at least two sites to cover Holocene optimum. High-precision AMS C-14 dating for the mid-bottom peat layers and radiometric Pb-210/Cs-137 dating for the upper horizons will be applied to offer precise dating. Identification and quantification of plant macrofossils will use an updated protocol of the Quadrat and Leaf Count Macrofossil Analysis technique (QLCMA). Peat humification will be determined by colorimetry using a standard procotol. Testate amoebae will be analysed by counting tests and produce continuous sets of testate amoebae data for the selected mires sections. Changing bog surface water table will be reconstructed using the transfer function between plant macrofossils and water table, combined with water table from testate amoebae and surface wetness from peat humification. Based on the changing water levels and the plants in ombrotrophic mires reflecting the prevailing climate, the time, magnitude, frequency and periodicity of climate change since Holocene optimum will be reconstructed from a synthesis of detailed high-resolution multi-proxy analysis of the cores from selected sites. The data from plant macrofossil/peat humification/testate aboebae will be compared with summarised proxy-climate datasets from mire-based isotope/ biomarker/ pollen/ phytolith and lake-sediment or tree-ring studies in the Changbai Mountains, northeast China, so as to produce valuable new perspectives on climate variation of China to inform climate modelling. The results from mires in China will be integrated with refined data from mires in the northern hemisphere to understand better the dynamics of climate since Holocene optimum. This project will try to explain the scientific questions as follows: How much, at what rate, and how often, climate has changed since Holocene optimum in Changbai Mountains, northeastern China? How is the "Medieval Optimum" and "Little Ice Age" manifested here? Did the climate change on decadal to centennial scales in the Holocene? The project will generate records from mires in northeastern China, and will create a multi-proxy database of the natural climte change in Holocene. The research will be of benefit for climate modellers to forecast the likely future direction, rate and magnitude of climate change.

研究全新世大暖期以来的气候变化可直接为人类适应未来变暖提供历史相似型。本项目选择对气候变化敏感的长白山区典型泥炭沼泽作为研究对象，以高分辨率的AMS C-14和Pb-210等手段定年，建立研究区气候-环境演变序列的年代标尺；在建立现代过程研究的基础上，通过对剖面植物大化石/腐殖化度/有壳变形虫分析，定量重建该区全新世大暖期以来的水位动态曲线；依据贫营养沼泽地表水位受控于有效降水这一特点，高精度重建以有效降水为代表的该时段气候变迁过程；通过与区内经典的温度或湿度序列对比，探讨控制沼泽表面水位变化的主要气候因素。该项目试图理解的科学问题有：全新世大暖期以来几十年分辨率的气候变化自然规律如何？是否存在短尺度的突然事件？千年尺度上沼泽表面水位变化的主导气候因素？本项目为进一步明晰变暖的气候下沼泽地表水位对气候的响应机制、高精度再现全新世大暖期以来气候自然变化、预测未来气候发展趋势提供科学依据。

研究全新世大暖期以来的气候变化可直接为人类适应未来变暖提供历史相似型。泥炭地与气候变化密切相关。长白山区是我国泥炭地最集中发育的地区之一。本项目选择区内不同纬度、不同经度和不同海拔的五处泥炭地（哈泥、金川、旱龙湾、兴隆、东方红），通过连续三年的生长季（5-10 月）对不同生境（丘、平地、洼地）内典型沼泽植物的样方调查，以及环境因子包括水位埋深、pH值、电导率、氧化还原电位、总氮、总磷、Ca、Mg含量的测试，得到了28种典型维管植物和10种苔藓植物水位埋深的最低值、最高值、平均值、中位数和变幅，其研究结果与欧洲或者北美的基本一致。通过典范对应分析和冗余分析，发现水位埋深是影响植物群落组成最主要的环境因子，在此基础上，建立了长白山区沼泽植物群落-水位埋深的转换函数模型。这是我国首个成炭植物-环境因子间的转换函数模型，为利用泥炭植物大化石定量重建全新世环境变化提供重要基础。..此外，在研究区内的哈泥、金川、老白山、圆池、赤池、东方红、锦北、白江河等泥炭地，利用人工法、表层取样器或者俄罗斯钻等采集剖面样品，利用Cs-137、Pb-210和AMS C-14法建立剖面的年龄-深度模型，通过植物大化石、腐殖化度、有壳变形虫、烧失量、碳累积速率以及Pb、Hg等指标，重建了研究区内大暖期以来沼泽地表湿度变化及其对应的气候变迁。整体上，长白山区在14500以来经历了干-湿-干-湿的交替变化过程，泥炭地记录了10.3 aBP、8.2 aBP、4.2 aBP、中世纪暖期和小冰期。高分辨率定量重建得到的中世纪温暖湿润，小冰期偏冷偏干，这与陈发虎等人的研究结果相一致，但是与欧洲小冰期冷湿组合相反。通过与附近的气象数据对比，发现重建的沼泽地表湿度在短时间尺度上受控于降水或有效降水，而在长时间尺度上受温度的影响更大。本项目可以为进一步明晰变暖的气候下沼泽地表水位对气候的响应机制、高精度再现全新世大暖期以来气候自然变化、预测未来气候发展趋势提供基础数据。