Lake Records of the Vegetational and Climatic History of Southwestern Siberia

该提案要求支持对位于西伯利亚西南部阿尔泰山脉阿克塔什（50 20′N, 87 35′E）以北的一大片冰川湖泊的研究。它们位于海拔约2000米的大片未森林地区，针叶林在邻近的山脊上延伸到2200米以上的林木线。湖泊沉积物将被取芯，通过花粉分析来确定这个鲜为人知的地区的植被和气候历史。研究将包括1998年在野外勘探工作中获得的另外两个山区湖泊和一个托木斯克附近平原湖泊的岩心。山区和平原的重点是草原/森林边界的历史，花粉分析显示，这是一个对气候变化敏感的过渡带。在阿尔泰山脉东北部的哈卡斯草原地区（北纬55度，东经90度），叶尼塞河流域海拔约200米的第二个地区，其边缘山脊上有以桦树和落叶松为特征的森林草原，邻近山脉海拔约750米以上的针叶林。这些主要过渡带的起伏将由湖泊沉积物的地层花粉分析来确定。草原的湖水从淡水到咸水，通过对沉积物的硅藻分析确定的盐度历史将补充花粉分析，以重建气候历史，因为硅藻可以敏感地记录盐度随时间的变化，特别是在北美大平原的广泛研究表明。

This proposal requests support for a study of a large cluster of lakes of glacial origin occurs north of Aktash (50 20' N, 87 35' E) in the Altai Mountains of southwestern Siberia. They are located in large unforested areas at elevations of about 2000 m with conifer forest extending on adjacent ridges up to tree line above 2200 m. The lake sediments will be cored to determine by pollen analysis the vegetational and climatic history of this little known area. Included in the study will be cores from two other lakes in the mountains and one in the plain near Tomsk, obtained during exploratory field work in 1998. The focus in both the mountains and the plain is on the history of the steppe/forest border, an ecotone of proven sensitivity to climatic change as revealed by pollen analysis. In a second area northeast of the Altai Mountains in the steppe region of Khakassia (55 N, 90 E), at elevations about 200 m in a basin of the Yenesei River, the bordering ridges contain forest steppe characterized by birch and larch, with taiga conifers at elevations above about 750 m in the adjacent mountains. Fluctuations of these major ecotones will he determined by stratigraphic pollen analysis of lake sediments. Lake waters in the steppe range from fresh to saline, and their salinity history as determined by diatom analysis of their sediments will supplement pollen analysis for the reconstruction of the climatic history, for diatoms can sensitively record changes in salinity over time, as has been shown especially by extensive studies in the North American Great Plains.