基于沉积硅藻定量重建的鄂西泥炭地全新世古水位和古pH变化及其气候驱动因子辨识

The response of peatland to climate change is a hotspot in the past global changes project. Both water table and pH are critical environmental factors for controlling peatland development, and hence quantitative reconstruction of past water table and pH is one of critical steps for improving our knowledge about peatland environmental change. Diatoms, an important group of algae in peatlands, are responsive to changes in water table and pH in peatlands. Until now, there is no available knowledge about quantitative reconstructions of peatland paleoenvironment from diatoms. This study plans to establish regional diatom-water table and diatom-pH transfer function models based on modern process analyses of surface-sediment diatoms and environmental parameters in Dajiuhu Peatland and Qizimeishan Peatland, western Hubei Province. Meanwhile, sedimentary chronology and multiple proxies (i.e. loss-on-ignition, grain size, biosilica and diatom) are analyzed in order to infer environmental change in these peatlands during the Holocene. Furthermore, quantitative reconstructions of past water table and pH are performed based on established transfer functions and sedimentary diatom assemblages. Correlation analyses between reconstructed water table and pH data and published data of regional paleo-rainfall and paleo-temperature will be conducted, which could help to investigate the climate drivers for past water table and pH changes. The study would enlarge the application of diatoms in peatland paleoenvironment research, and provide new methods for quantitative reconstruction of peatland paleoenvironment. The results could provide important reference information for forecasting the response of these peatlands to future climate changes.

泥炭地对气候变化响应是过去全球变化研究计划中的热点内容。水位和pH是调控泥炭地发育的关键环境因子，定量重建古水位和古pH变化是当前深入认识泥炭地环境变化的关键节点之一。硅藻是泥炭地中重要的藻类类群，对泥炭地水位和pH变化响应敏感，但目前尚没有开展基于硅藻定量重建泥炭地古环境工作。本研究拟以鄂西大九湖泥炭地和七姊妹山泥炭地为研究地，通过泥炭表层硅藻和环境因子现代过程分析，建立区域硅藻-水位和硅藻-pH转换函数模型。同时，分析泥炭岩芯年代学以及烧失量、粒度、生物硅和硅藻指标，综合判识泥炭地全新世环境演化过程。进而结合转换函数和沉积硅藻组合定量重建全新世古水位和古pH，并与已发表的区域古降水量和古温度数据进行相关分析，辨识古水位和古pH变化的主要气候驱动因子。本研究拓展了硅藻在泥炭地古环境研究中的应用，为泥炭地古环境定量重建提供新方法，并为预估泥炭地对未来气候变化响应提供重要依据。

泥炭地对气候变化响应敏感是过去全球变化研究计划中的热点内容。水位是调控泥炭地发育的关键环境因子，定量重建古水位是当前深入认识泥炭地环境变化的关键节点之一。硅藻是水生生态系统重要初级生产者，对环境变化响应敏感并被广泛应用于湖泊古环境定量重建，但目前泥炭地硅藻研究报道很少。本研究在对鄂西七姊妹山、二仙岩和大九湖泥炭地表层样品硅藻和环境因子调查发现硅藻敏感响应于水位、pH和阳离子浓度变化。在此基础上，本研究重点以大九湖泥炭地为研究对象，进行硅藻和环境因子季节监测，硅藻季节变化主要响应于水位和磷酸根浓度变化。同时，对大九湖四号湖和养鹿场两处浅孔岩芯硅藻进行分析，发现硅藻组合在20世纪60年代发生明显变化，结合表层硅藻-环境因子数据库，推测大九湖湿地水位埋深变浅（湿润），同时营养水平上升。考虑到亚热带泥炭地呈小斑块状和微生境影响，项目组以东北地区5处开阔泥炭藓湿地为研究对象，初步建立了硅藻-水位转换函数模型，并应用到阿尔山泥炭地硅藻沉积记录中，重建近百年来的水位变化与降水量存在良好对应关系。本研究揭示亚热带和温带地区泥炭地硅藻生物多样性，及其与环境因子的关联，为我国泥炭地环境变化研究提供了新的技术手段。尤其是东北地区硅藻-水位转换函数将为泥炭地古水位定量重建提供新的方法。