Response of tundra ecosystem in southwestern Alaska to Younger-Dryas climatic oscillation
Response of tundra ecosystem in southwestern Alaska to Younger-Dryas climatic oscillation
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DOI：
10.1046/j.1365-2486.2002.00550.x
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发表时间：
2002-11
影响因子：
11.6
通讯作者：
F. Hu;B. Lee;D. Kaufman;Sumiko Yoneji;D. Nelson;Paul D. Henne
中科院分区：
文献类型：
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作者：
F. Hu;B. Lee;D. Kaufman;Sumiko Yoneji;D. Nelson;Paul D. Henne
在最后一次冰川-间冰期转变(LGIT)期间，气候变暖被向类似冰川的条件逆转所打断。生态系统变化的古记录有助于记录这些事件的地理范围，并提高我们对生物对气候强迫的敏感性的理解。为了重建生态系统和气候变化，我们分析了阿拉斯加西南部湖泊沉积物的化石花粉组合、生物硅含量(BSiO_2%)和有机碳含量(OC%)。大约13 600 CAL BP(称为 BP：14C)左右，桦树苔原取代草本植物苔原成为该地区的主要植被(称为 BP：14C，校准历年之前)，从桦树孢粉百分比的增加推断，从<；<； 5%到>；>；>； 20%与莎草科、禾本科和蒿属相关的减少。空中交通管制。13000Cal BP，桦木层厚度从28 下降到 5%，表明灌木冻土带已恢复为草本冻土带。灌木冻土带取代草本植物冻土带，在11 600 ，即 BP恢复为优势植被。较高的OC%和BSiO_2%值表明灌丛-冻土带时期比草本-冻土带时期土壤更稳定，水生生产力更高，尽管在此之前花粉变化滞后于生物地球化学指标的变化。13 000 Call BP。将我们的古生态数据与格陵兰岛冰芯dδ18O的记录进行比较，发现从年轻仙女木(YD)的开始到终止都有惊人的相似模式。这种相似性支持了这样一种假设，即与北大西洋地区一样，北太平洋地区也发生了明显的YD气候振荡。YD结束时生态变化的速度和幅度与温室实验和显示冻土带对气候强迫敏感的历史照片是一致的。
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%).Betulashrub tundra replaced herb tundra as the dominant vegetation of the region around 13 600 cal BP (cal BP:14C calibrated calendar years before present), as inferred from an increase ofBetulapollen percentages from << 5% to >> 20% with associated decreases in Cyperaceae, Poaceae, andArtemisia. Atc. 13 000 cal BP, a decrease ofBetulapollen 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 beforec. 13 000 cal BP. Comparison of our palaeoecological data with the ice‐core dδ18O 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.