Last glacial vegetation reconstructions in the extreme-continental eastern Asia: Potentials of pollen and n-alkane biomarker analyses
Last glacial vegetation reconstructions in the extreme-continental eastern Asia: Potentials of pollen and n-alkane biomarker analyses
复制标题
DOI：
10.1016/j.quaint.2012.04.007
复制
发表时间：
2013-03
影响因子：
2.2
通讯作者：
P. Tarasov;S. Müller;M. Zech;D. Andreeva;B. Diekmann;C. Leipe
中科院分区：
文献类型：
--
作者：
P. Tarasov;S. Müller;M. Zech;D. Andreeva;B. Diekmann;C. Leipe
目前的研究提供了树木覆盖率，年降水量和平均7月温度的定量重建来自Billyakh湖（65°17′N，126°47′E，海拔340米）的花粉记录，跨越最近的ca。50 ka（ca. 50，000卡年）。树木覆盖的重建表明，木本植物的存在，通过整个分析的时间间隔，虽然树木在Billyakh湖周围的植被在14 ka BP（<5%）之前只发挥了很小的作用。这一结果证实了树木花粉的低百分比和低分数的冷落叶林生物群系在PG 1755记录从比里亚赫湖。最暖月平均温度的重建值为108 -10 °C，不支持Billyakh湖周围的落叶松林或林地在末次冰期最冷的阶段（1032 - 1015 ka BP）。然而，来自北方西伯利亚的现代病例。在比里亚赫湖以北750公里处，表明个别落叶松植物可以在7月平均气温约8 °C的极低温度下在灌木和草地苔原景观中生长。这使得上扬斯克山脉的西部和南部前陆可以提供足够潮湿和温暖的微生境，并允许个体落叶松标本在末次冰期的极端气候中生存的假设变得合理。重建的末次冰期年降水量平均值约为270 mm。这一数值比西伯利亚东北部比利亚赫湖以东的极端大陆平均值高出近100毫米，目前那里生长着以落叶松为主的冷落叶林。这表明，比里亚赫湖周围的末次冰期环境从来没有太干燥落叶松生长，夏季温暖不足是主要因素，这限制了树木生长在末次冰期。西伯利亚植物的正构烷烃分析表明，在这项研究中，相当复杂的烷烃分布模式，这挑战了化石记录的解释。特别是，极低的正烷烃浓度在当地的针叶树和灌木的树叶表明，他们的贡献，因此，化石湖泊沉积物可能不高，以追踪第四纪历史的针叶类群使用正烷烃生物标志物的方法。
The current study presents quantitative reconstructions of tree cover, annual precipitation and mean July temperature derived from the pollen record from Lake Billyakh (65°17′N, 126°47′E, 340 m above sea level) spanning the last ca. 50 ka (ca. 50,000 cal yrs). The reconstruction of tree cover suggests presence of woody plants through the entire analyzed time interval, although trees played only a minor role in the vegetation around Lake Billyakh prior to 14 ka BP (<5%). This result corroborates low percentages of tree pollen and low scores of the cold deciduous forest biome in the PG1755 record from Lake Billyakh. The reconstructed values of the mean temperature of the warmest month ∼8–10 °C do not support larch forest or woodland around Lake Billyakh during the coldest phase of the last glacial between ∼32 and ∼15 ka BP. However, modern cases from northern Siberia, ca. 750 km north of Lake Billyakh, demonstrate that individual larch plants can grow within shrub and grass tundra landscape in very low mean July temperatures of about 8 °C. This makes plausible the hypothesis that the western and southern foreland of the Verkhoyansk Mountains could provide enough moist and warm microhabitats and allow individual larch specimens to survive climatic extremes of the last glacial. Reconstructed mean values of annual precipitation are about 270 mm during the last glacial interval. This value is almost 100 mm higher than modern averages reported for the extreme-continental north-eastern Siberia east of Lake Billyakh, where larch-dominated cold deciduous forest grows at present. This suggests that last glacial environments around Lake Billyakh were never too dry for larch to grow and that the insufficient summer warmth was the main factor, which limited tree growth during the last glacial interval. The n-alkane analysis of the Siberian plants presented in this study demonstrates rather complex alkane distribution patterns, which challenge the interpretation of the fossil records. In particular, extremely low n-alkane concentrations in the leaves of local coniferous trees and shrubs suggest that their contribution to the litter and therefore to the fossil lake sediments might be not high enough for tracing the Quaternary history of the needleleaved taxa using the n-alkane biomarker method.