长白山区雨养型泥炭地晚全新世古水位定量重建

Paleoenvironmental study is an ongoing hot issue in the Earth science. Due to the complexity of the Earth system and occasionality of profile recovery, there are still many uncertainties about paleoenvironment changes. It calls for more reliable, quantitive records from areas in various geographical contexts, especially some poorly studied areas. Ombrotrophic bog is an ideal archive because it reveives all its moisture directly from the atmosphere and is particularly sensitive to hydroclimate changes. In this study, we will take multi-cores from four recently discovered ombrotrophic bogs in Changbai Mountains. Paleo-water table will be quantitively recontructed by testate amoebae analysis, with the previously developed tesatate amoebae-water table transfer function. Chronology of peat profiles will be provided by 210Pb/137Cs and AMS14C dating. On this basis, together with correlating the marker tephra layers, we will conduct a detailed comparison, within-site and inter-site, to discrimate the local signals and regional/global signals. Combining with macrofossil and huminification proxy records, and other paleoenviornmental records(pollen, peat cellulose δ13C, treering ) from vicinity of the study area, we will reasonably interprete the water table dynamics in ombrotrophic bogs in Changbai Montains during late Hocene. By correlating the water table curves with volcanic eruption, solar activity, and other typical records of Asian monsoon and global climate events, we attampt to explore the potential drivers and mechnisms of water talbe fluctuation in ombrotrophic bogs in Changbai Montains. The results of this study will provide new knowledge for comprehensively and deeply understanting the envolving process and principles of peatlands in Northeast China. Also, it can provide new data for global comparative study(Europe, western Siberia, East Asia, North America) based on water table reconstruction from ombrotrophic bogs.

古环境研究是地球科学领域的持续热点，由于地球系统的复杂性和环境重建的偶然性，我们对环境变化过程和规律的认识仍存在诸多不确定，这需要更多来自研究薄弱地区的、可靠的、定量化的环境记录。本项目选择长白山区最新发现的4个忠实记录环境变化的雨养型泥炭地，以有壳变形虫为代用指标，运用已建立的转换函数，定量重建古水位；210Pb/137Cs和AMS14C法建立剖面的精确年代标尺，结合火山灰标志层，通过泥炭地内与泥炭地间的剖面对比，探讨影响水位变化的内生和外生因素，甄别水位记录的局地、区域/全球变化信息；结合植物大化石、腐殖化度，以及周边其它记录(孢粉、同位素、树轮)，准确解译水位反映的区域环境变化；对比太阳活动、火山活动、典型亚洲季风和全球气候事件记录，探讨晚全新世以来长白山雨养型泥炭地水位变化的动力与机制。研究结果有助于全面深入认识东北地区泥炭地演化过程和规律，亦可为全球尺度泥炭古环境对比提供新数据。

水是泥炭沼泽形成和发育的关键因素。同时泥炭沼泽水位受降水、温度的影响，能够反映区域气候变化。因此，古水位研究是泥炭地古环境研究的理想切入点。本项目的目标是定量重建长白山区雨养型泥炭地晚全新世以来的古水位变化，研究本区域泥炭地水位变化的规律，探讨影响水位变化的因素和机制。我们首先优化了本区有壳变形虫-水位转换函数，增加了一些本区新记录物种。完善后的转换函数具有良好的预测性能（RMSEP=5.32cm，R2=0.82）。在可靠年代框架基础上，我们基于老里克泥炭剖面，通过有壳变形虫、植物大化石、粒度、C、N、δ13C、δ18O等多指标研究揭示了全新世以来长白山区的气候变化过程。我们采用有壳变形虫指标定量重建了长白山区多个晚全新世泥炭地古水位记录。泥炭地间、泥炭内部多种剖面间对比分析表明，泥炭地水位变化与气候变化具有很强的一致性，即在温暖时期，泥炭地水位低，而寒冷时期，水位则相对较高，显示温度影响的泥炭地蒸散发对水位具有决定性作用。这印证了欧洲同类研究指出的随着气候大陆性增加，温度对水位的影响增强的结论。我们在强调了气候控制作用的同时，也明确了内生过程泥炭地水位的影响，泥炭的不断累积可使泥炭地水位呈不断下降的趋势。此外，我们也揭示了地形、火山活动等因素影响泥炭地水位对气候变化响应的敏感性。