东昆仑阿拉克湖地区近2ka以来风成沙沉积的气候变迁记录

对青海都兰县巴隆乡阿拉克湖东岸风成沙剖面的孢粉分析结果表明，该地区气候近2ka来经历了4个温暖期与寒冷期交替阶段：温暖期出现在20～180，330～410，700～920，1140～1380a；寒冷期出现在180～330，410～700，920～1140，1380～1920乱温暖期气候为温干偏湿，寒冷期气候为温凉干旱．其中700～920a出现丰富的常见于亚热带和温带地区的漆树、乔木植物发育的孢粉组合，是近2ka中该地区气候最为温暖和潮湿的时期，提供了西部也存在与东部唐代温暖期对应的证据．1500a以后沉积的风成沙中已找不到足够能分析环境的孢粉数量，说明进入“小冰期”后无论是乔木植物还是草本植物的数量都迅速减少，到现代该地区乔木植物已基本绝灭．考虑到该地区人口密度很低，人类活动不应成为造成该地区乔木植物绝灭的根本原因，笔者认为主要原因应归为长达300多年的“小冰期”寒冷和干旱气候的自然因素．

Climate Variance Record of Aeolian Sand in Recent 2 ka, Alakehu Area, Eastern Kunlun Mountains

Sporopollen analysis to aeolian sand section at the east bank of the Alakehu, eastern Kunlun, shows a climate variance process in recent 2 000 a which happened 4 periods of warm and cold alternation. The warm periods occurred during 20-180, 330-410, 700-920 and 1 140-1 380 a respectively, and the cold periods during 180-330, 410-700, 920-1 140 and 1 380-1 920 a. The climates were warm-dry-slightly damp during warm periods and warm-slightly cold and dry during cold period. 700-920 a is the warmest and dampest period in recent 2 000 a, which is implied by the rich of rhus, that mainly distribute in semitropical zone and temperate zone and also rich of arbor sporopollen, and is accorded to the warm period of eastern China in Tang Dynasty which is recorded by the history documents. After 1 500 a, lacking of sporopollen shows that either arbor or herbage decreased sharply when the Little Ice Age came and became almost extinct nowadays. The authors suggest that cooling and drying in (about) 300 a the Little Ice Age is the main reason to the extinction of the arbor, not the people activity.