京杭大运河沿线第四纪植被变迁分析

京杭大运河是世界上开凿最早、规模最大、里程最长的人工河流。笔者以运河区域内第四纪古植物证据为基础，对孢粉植物群的组成、区系成分和生态功能类型进行了分析，对第四纪植被进行了重建。结果显示：该区域共有陆地植物105科；植物区系以温带成分为基本骨架，具有温带和热带过渡性质，反映出干湿交替、冷暖更替和水陆镶嵌的古环境特点。点多样性指数显示，北部为22～68个科（属），南部为65～117个科（属）。孢粉植物群划分为13个生态功能类型。运河沿线中全新世森林植被自北而南分为凉温带针阔混交林、温带落叶阔叶林、暖温带常绿落叶阔叶混交林，以及亚热带常绿阔叶林4个植被带。影响运河沿线第四纪植被变迁的主要因素有第三纪植物遗存、第四纪气候变迁和早期人类活动等。

Analysis of Quaternary vegetation changes along the Beijing-Hangzhou Grand Canal

The Beijing-Hangzhou Grand Canal is the earliest in excavation,the largest in watershed and the longest in mileage for man-made rivers in the world.Based on the paleobotanical evidence during the Quaternary along the canal,genus and family composition,floristic composition,and ecological function types of the palynoflora were analyzed in this paper.The Quaternary vegetation was reconstructed.The results are as follows: There are 105 families of land plants recognized.Temperate floristic elements can be viewed as the basic framework in this flora,with temperate and tropical transitional nature.This flora also reflect the following environmental fluctuations,e.g.alternation of wet and dry conditions,replacement of warm and cold climate,and mosaic of land and water environment.The index of point diversity is 22—68 families(genera) in the north,and 65—117 in the southern.Palynoflora along the canal can be divided into 13 types of ecological function.Along the canal,the mid-Holocene forest vegetation,from north to south,can be divided into four categories: cool-temperate mixed coniferous and deciduous forest zone,temperate deciduous broad-leave forest zone,warm temperate evergreen and deciduous broad-leave forest zone,and subtropical evergreen broad-leave forest zone.The main factors affecting the Quaternary vegetation change along the canals are the Tertiary plant residues,Quaternary climate change and early human activities.