全新世中国热带北界变迁的探讨

SHIFT OF THE NORTH BOUNDARY OF CHINA'S TROPICS DURING HOLOCENE

本文根据孢粉、动物群、石笋、珊瑚礁、红树林等约 30个全新世古环境分析实例 ,认为年均气温变化 2℃左右 ,就会引起热带界线的变动。热带北界的迁移过程可分 3个阶段 :全新世回暖期北返阶段 ( 1 1 0 0 0～ 85 0 0aB .P .) ,热带北界北移 1 .5个纬度 ;升温期北进阶段( 85 0 0～ 5 0 0 0aB .P .) ,向北推进 3～ 5个纬度 ;降温期南归阶段 ( 5 0 0 0～ 30 0 0aB .P .) ,向南回归 1～ 4个纬度。热带北界的展布既有纬度地带性 ,也有经度地带性 ,这与东亚季风、寒潮、台风的影响以及地形格局有关。

According to paleoenvironmental analyses of about thirty examples related to spore-pollen, mam malia fauna, stalagmite, coral reef and mangrove, shift of the northern boundary of China's tropics during Holocene are discussed in this paper. Three stages of shift were recognized. The first stage was in Early Holocene (11 000～8 500?aB.P.), corresponding to a warming time, with the north boundary moving 1.5° northwards, i.e. from about 22°N, which was the north boundary during the Last Glacial Maximum, to about 23.5°N. The second stage was in Middle Holocene( 8 500～ 5 000?aB.P.) , corresponding to a temperature rising time, with the north boundary moving 3°～ 5° northwards. The third stage was in Late Holocene(5 000～3 000?aB.P.), corresponding to a temperature-dropping time, with the north boundary returning 1°～4°. Some elements such as the East Asia Monsoon, cold tide, typhoon and landform to influence shift of the north boundary were discussed in this paper.