摘要
西藏东南部封闭湖泊高分辨率的花粉记录反映，在１６ ｋａ ＢＰ以前花粉组合以藜科（Ｃｈｅｎｏｐｏｄｉａｃｅａｅ） 和蒿属（Ａｒｔｅｍｉｓｉａ） 为主，花粉浓度很低，应为荒漠草原植被。当时气候寒冷干燥，１ 、７ 月份和年均温分别低于现在当地７ ～１０ ℃，０．５～１．５ ℃和４～６ ℃。年降水量仅２５０ ｍｍ 是现今当地年降水量的４０ ％ ；１２ ｋａ ＢＰ以后气温和降水逐渐增加，出现木本植物花粉，桦属（ Ｂｅｔｕｌａ） 和松属（ Ｐｉｎｕｓ）等，在９ ．２～５ ｋａ ＢＰ发育森林或森林草甸；８～６ ｋａ ＢＰ是研究区气候最适宜期，１、７ 月份气温均高于现在２～３ ℃，年降水量比现在当地高１００ ｍｍ 左右；５．５ ｋａ ＢＰ以后气温和降水呈非线性下降，主要发育草原植被。
Studies on the pollen from cores of Lake Hidden (29°48.77′N, 92°22.37′E) and Ren Co (30°43.97′N, 96°40.97′E) in Southeast Xizang (Tibet) showed climatic changes and the evolution of vegetation since the Last Glacial Maximum (LGM). Before 16 ka BP pollen assemblages were dominated by Chenopodiaceae (20%～50%) and Artemisia (10%～30%) and pollen influx values were very low from Lake Ren Co in Basu county. The vegetation around the lake was probably a desert_steppe during the LGM. The data also suggest that the climate in the Basu area was cold and dry during the LGM and the last glacial time. The mean annual temperature was probably 4～6 ℃ colder than the present, and the mean annual precipitation was only 250 mm, about 40% of the present. The Southwest monsoon became stronger from 12 ka BP to 6 ka BP reaching its acme by 7 ka BP, but weakened gradually from 5 ka BP to the present. The paleovegetation was dominantly forest or forest_meadow around Lake Hidden and Ren Co during the 9.2～5 ka BP. The mean temperature in January was probably 2～3 ℃ higher than the present, and the mean annual precipitation was 100 mm more than the present. The timing of vegetational and climatic changes based on pollen records generally supports the results of global climatic_model experiments that predict a strengthened monsoon system during the early to middle Holocene followed by a weakened monsoon system.
基金
国家自然科学基金
关键词
南亚季风
花粉记录
西藏东南部
古植被与古气候
South Asia monsoon, Pollen records, Southeast Tibet, Paleovegetation and paleoclimate
