长江中游泥炭湿地有壳变形虫生态学与全新世古水位重建

Peatlands play key roles in the global carbon cycle, biodiversity conservation, and regulation of climate and water resources. The widely distributed, well preserved Sphagnum-dominated peatlands in the region of middle Yangtze reach are supporting a good chance for studying the past environmental variability during the Holocene. Previous researches mainly focused on the temperature reconstructions using different proxies in the region. However, few studies were carried out on surface moisture, wetness, water table depth and hydrology in peatlands, which are highly related to regional precipitations. The main reason is lacking of a robust proxy which can be used for the paleo-precipitation reconstructions. Testate amoebae, a kind of protists, as their high abundant, wide distribution and sensitive to surface moisture of peatland, have proved as an excellent proxy for precipitation reconstruction during the Holocene, . Testate amoebae are unicellular protists that build a test (shell), in which a single amoeboid cell is enclosed. They are estimated to represent 5–30% of the total microbial biomass at the surface of Sphagnum peatlands. Their ecology, diversity, and biogeography were studied in in peatlands of many parts of the world. Over the past couple of decades, a considerable amount of research has been directed toward quantifying and modeling relationships among testate amoebae and depth to water table, so that community composition can be used for quantitative paleoenvironmental and biomonitoring applications. These studies have consistently revealed the importance of hydrological variables in controlling community composition and have generally found particularly good relationships between community composition and the depth of the local water table. In addition, because they can produce decay-resistant and morphologically distinct shells, or tests, testate amoebae are useful tools to reconstruct the changes of hydroclimate by application of hydrological transfer functions to palaeoecological records in peats and sediments..This project therefore are to:.1. Investigate the diversity and ecology of testate amoebae from peatlands near the middle Yangtze Reach, and determine the major environmental correlates of testate amoeba community structure..2. Develop a testate amoebae based hydrological transfer function model for central China. Compare results to those of previous studies from around the world to assess the similarity of amoeba communities and the consistency of amoeba hydrological preferences. .3. Reconstruct the paleohydrological processes based on fossil testate amoebae from peatlands sediments and the modern hydrological transfer function. Combine other paleoclimate proxies and 14C age data, discuss the climate variability and events during the Holocene, with particular reference to the past hydrology and precipitation.

泥炭湿地作为一种重要的生态系统在全球变化、生物多样性和水循环方面发挥着重要作用，长江中游大面积分布且沉积较厚的泥炭湿地是研究该地区古环境变化的良好载体。前期开展的大量研究主要集中在对古温度的重建，但是对于湿地的表层湿度、含水量、水位等与降水信号密切相关的研究却十分薄弱，主要瓶颈在于缺乏可靠的对水位敏感的代用指标。在泥炭湿地表面大量生活且对湿度（水位）敏感的有壳变形虫为解决之一问题提供了新的途径。此类研究在国际上已广泛应用于湿地的古水位重建，但在我国的发展仍十分缓慢。. 本研究将开展长江中游亚高山泥炭湿地现代有壳变形虫的生态学调查，识别出在水位和湿度梯度上的不同指示种，建立 “属种-水位（或含水量）”的转换函数，结合泥炭沉积物中的有壳变形虫化石数据和年代学资料，定量重建泥炭湿地全新世高分辨率的古水位变化，间接地指示古降水变化，最终建立适合该地区的泥炭湿地水位变化的代用指标。

长江中游大面积分布且沉积较厚的泥炭湿地是研究该地区古环境变化的良好场所。前期开展的大量研究主要集中在对古温度的重建，但是对于湿地的表层湿度、含水量、水位等与降水信号密切相关的研究却十分薄弱，主要瓶颈在于缺乏可靠的对水位敏感的代用指标。在泥炭湿地表面大量生活且对湿度（水位）敏感的有壳变形虫为解决之一问题提供了新的途径。此类研究在国际上已广泛应用于湿地的古水位重建，但在我国的发展仍十分缓慢。. 本项目以长江中游几个典型的亚高山泥炭湿地作为研究地点，开展了这些湿地的现代生态监测，调查了其中的有壳变形虫分布、多样性、群落结构和在生态梯度上的响应规律。主要有以下发现：.1）长江中游地区亚高山泥炭地有壳变形虫的种类十分丰富，多样性高，大约发现有壳变形虫60多个物种或类群，发下了一个新物种“九湖梨壳虫Nebela jiuhuensis”；.2）发现有壳变形虫对泥炭地的水位变化十分敏感，通过野外调查和生态梯度分析，，识别出在水位和湿度梯度上的不同指示种，常见的干旱指示种有：Trigonopyxis arcula, Assulina muscorum, Euglypha rotunda, A. seminulum, 指示极端湿润环境的主要有Centropyxis ecornis，Difflugia oblonga, D. lanceolata, Nebela jiuhuensis, Argynnia caudate等物种或类群。.3）建立了地区性的有壳变形虫 “属种-水位”的转换函数，并尝试将大九湖泥炭地一个浅钻孔中的有壳变形虫化石数据和该转换函数相结合，重建了该泥炭地的古水位变化曲线。.4）该项目把有壳变形虫这一对水位敏感的代用指标应用到泥炭地的古水文重建，为将来在较长时间尺度上和较大空间尺度上开展泥炭地的古水文、古环境和古气候重建打好了坚实基础。在该项目的支持下，在国内外学术期刊上发表了关于有壳变形虫的分类、湿地生态监测、古水文重建等主题的研究论文。