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Response of tundra ecosystem in southwestern Alaska to Younger-Dryas climatic oscillation

机译：阿拉斯加西南部的苔原生态系统对Younger-Dryas气候振荡的响应

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Climatic warming during the last glacial-interglacial transition (LGIT) was punctuated by reversals to glacial-like conditions. Palaeorecords of ecosystem change can help document the geographical extent of these events and improve our understanding of biotic sensitivity to climatic forcing. To reconstruct ecosystem and climatic variations during the LGIT, we analyzed lake sediments from southwestern Alaska for fossil pollen assemblages, biogenic-silica content (BSiO2 %), and organic-carbon content (OC%). Betula shrub tundra replaced herb tundra as the dominant vegetation of the region around 13 600 cal BP (cal BP: (14) C calibrated calendar years before present), as inferred from an increase of Betula pollen percentages from < 5% to > 20% with associated decreases in Cyperaceae, Poaceae, and Artemisia . At c . 13 000 cal BP, a decrease of Betula pollen from 28 to < 5% suggests that shrub tundra reverted to herb tundra. Shrub tundra replaced herb tundra to resume as the dominant vegetation at 11 600 cal BP. Higher OC% and BSiO2 % values suggest more stable soils and higher aquatic productivity during shrub-tundra periods than during herb-tundra periods, although pollen changes lagged behind changes in the biogeochemical indicators before c . 13 000 cal BP. Comparison of our palaeoecological data with the ice-core ddelta(18) O record from Greenland reveals strikingly similar patterns from the onset through the termination of the Younger Dryas (YD). This similarity supports the hypothesis that, as in the North Atlantic region, pronounced YD climatic oscillations occurred in the North Pacific region. The rapidity and magnitude of ecological changes at the termination of the YD are consistent with greenhouse experiments and historic photographs demonstrating tundra sensitivity to climatic forcing. [References: 42]
机译：上一次冰期至冰期间过渡（LGIT）期间的气候变暖因逆转至类似冰河的条件而中断。生态系统变化的古记录可以帮助记录这些事件的地理范围，并增进我们对生物对气候强迫的敏感性的理解。为了重建LGIT期间的生态系统和气候变化，我们分析了阿拉斯加西南部的湖泊沉积物的化石花粉组合，生物硅含量（BSiO2％）和有机碳含量（OC％）。桦树灌木冻原取代了草本冻原，成为13 600 cal BP附近区域的主要植被（cal BP：（14）C校准的日历年，直到现在），这是由于桦树花粉的百分比从<5％增至> 20％推断的莎草科，禾本科和蒿的相关减少。在c处。 13 000 cal BP，桦木花粉从28降低到<5％，表明灌木冻原恢复为草本冻原。灌木冻原代替草本冻原恢复为11 600 cal BP的主要植被。尽管花粉的变化滞后于c之前的生物地球化学指标的变化，但较高的OC％和BSiO2％值表明灌木冻原期比土壤冻土期更稳定的土壤和较高的水生生产力。 13000 cal BP。我们的古生态数据与格陵兰岛冰芯ddelta（18）O记录的比较显示，从开始到终止年轻树蛙（YD）的方式都惊人地相似。这种相似性支持这样的假设，即在北大西洋地区，北太平洋地区发生了明显的YD气候振荡。 YD终止时生态变化的速度和幅度与温室试验和历史照片一致，表明苔原对气候强迫的敏感性。 [参考：42]

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