干旱区生态环境知识资源中心

Sediments spanning the last 30000 yr BP were obtained from two sections in the southern part of the Tengger Desert, northwestern China (38degrees10’46 "N, 102degrees45’53 "E). The pollen assemblage suggested a Picea forest domination under a wetter and cooler environment from 27580 to 23510 yr BP. During the following period from 23510 to 21880 yr BP a Cyperaceae meadow occurred under a wet and cold climate. Wetter and cooler conditions returned and a Picea forest re-occupied this region between 21880 and 20910 yr BE Front 20910 to 15590 yr BP a steppe under a dry environment dominated the region. The first temperature increase started at ca.15590 yr BP. The pollen assemblage covering the period between 15590 and 10890 yr BP can be divided into six minor zones, suggesting that the vegetation compositions changed rapidly under unstable climate. Between 10710 and 10370 yr BP the climate became cold and dry again. The climatic conditions became warmer and more humid between 10260 and 9140 yr BE From 8450 to 7950 yr BP a steppe landscape under a dry climate occupied this region. Between 7950 and 7290 yr BP climate seemed more humid. The folio-wing period from 7290 to 5670 yr BP was generally warm. The period between 5670 and 3510 yr BP was characterized by dramatic climatic oscillations. Relatively cold intervals appeared around 7760 and 7380, 64906290, 5670-5010, 4470-3510 yr BP. Two pronounced dry events occurred in 6290-5670 and 5010-4470 yr BP with a marked wet spell from 3510 to 3000 yr BP.