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首页> 外文期刊>Journal of paleolimnology >Late Holocene paleoenvironmental change in a Great Lakes coastal wetland: integrating pollen and diatom datasets
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Late Holocene paleoenvironmental change in a Great Lakes coastal wetland: integrating pollen and diatom datasets

机译：大湖沿岸湿地晚新世古环境变化：整合花粉和硅藻数据集

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Multiple proxy indicators are regularly used to present robust arguments for paleoenvironmental change. We use fossil pollen and diatoms from,a 495-cm core taken from Cootes Paradise, a coastal wetland in the western end of Lake Ontario, to investigate ecological changes in the late Holocene. We use consensus analysis to demonstrate that pollen diagrams are best zoned after the data have been split into source area, in this case upland and wetland taxa, because each group responds differently to environmental change. We also use consensus analysis to demonstrate the sensitivity of clustering to the distance measure used. The record begins at 2400 C-14 years BP, when the wetland was dominated by shallow water emergents and epiphytic diatoms. At 2100 14C years BP, a decline in the epiphytic diatoms Epithemia spp., a rise in Poaceae (cf. Zizania aquatica) pollen and a coincident increase in pollen concentration suggest a water level rise at this time. At about 800 C-14 years BP, the diatom record shows a pulse in small benthic Fragilaria species; shortly after, a shift occurs in the upland tree pollen spectra involving an increase in Pinus and a decline in Fagus. This shift in upland forest trees has been associated elsewhere with the Little fee Age and the diatom data present some evidence for impacts of this climatic event on aquatic systems. The diatom and pollen records both indicate large changes associated with the effects of European settlement, including rises in Ambrosia as well as Typha angustfolia pollen. Planktonic diatoms dominate post-settlement assemblages indicating large-scale hydrological and ecological changes, probably associated with the introduction of carp and alterations to the Iroquois bar which separates the wetland from Lake Ontario. Our work at Cootes Paradise is important for multi-proxy coastal wetland studies in general, in addition to the late Holocene environmental history and prehistory of the Great Lakes region.
机译：经常使用多个代理指标来提出有关古环境变化的可靠论据。我们使用化石花粉和硅藻（来自安大略湖西端沿海湿地库克斯天堂（Cootes Paradise）的495厘米岩心）调查了全新世晚期的生态变化。我们使用共识分析来证明在将数据划分为源区域（在此情况下为高地和湿地分类单元）后，花粉图最好进行分区，因为每个组对环境变化的响应不同。我们还使用共识分析来证明聚类对所用距离度量的敏感性。记录始于BP 2400 C-14年，当时湿地被浅水喷头和附生硅藻所占据。在BP 2100 14C年，附生硅藻Epithemia spp。的下降，禾本科（Poaceae）（参见Zizania aquatica）花粉的上升以及花粉浓度的同时上升表明此时水位上升。在大约BP 800 C-14岁时，硅藻记录显示出小型底栖的草莓属植物有脉动。此后不久，山地花粉光谱发生了变化，包括松树增加和Fagus减少。旱地林木的这种变化在其他地方与“小费时代”有关，硅藻数据为这种气候事件对水生系统的影响提供了一些证据。硅藻和花粉的记录均表明与欧洲定居的影响有关的变化很大，包括安布罗西亚和香蒲的花粉增加。浮游性硅藻在沉降后的组合中占主导地位，表明大规模的水文和生态变化，可能与鲤鱼的引入和易洛魁河条的改变有关，易洛魁河条将湿地与安大略湖分开。除了晚新世环境历史和大湖地区的史前史之外，我们在Cootes Paradise的工作对于总体而言对多代理沿海湿地研究也很重要。

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