河西山地绿洲荒漠植物群落种群多样性研究Ⅰ生态地理及植物群落的基本特征

A Study on the population diversity of plant community in Hexi mountain oasis desert area:Ⅰ General features

河西山地绿洲荒漠区包括祁连山北坡中段森林草原区、张掖荒漠绿洲区和东大山森林草原区等 3个地理地段 ,海拔在 1450～ 4 2 0 0 m之间。近 50年气候的变化趋势是 2 0世纪 6 0年代冬冷夏热春雨多 ;70年代冬暖夏冷 ,夏秋雨多 ;80年代至本世纪末 ,年平均气温偏低 ,降水量增加。相应地 ,祁连山发育的现代冰川今后将出现稳定乃至前进现象。黑河流量动态变化与降水量的变化趋势一致。主要植被类型有红砂荒漠、山地荒漠草原、典型草原、寒温性针叶林、高山灌丛及高山流石滩植被等。祁连山北坡产高等植物 10 6 4种。植物区系从区系特征上可以分为两个区系小区 ,即祁连山北坡中段、东大山森林草原区和河西荒漠区。东大山与祁连山北坡中段属于同一个植物区系类型 ,是一个年轻衍生的温带植物区系 ,区系发生在晚第三纪至第四纪。河西荒漠区是一个古老的植物区系。维管植物生活型谱组成中 ,地面芽植物占优势 ,其次是高位芽植物、一年生植物、隐芽植物和地上芽植物 ,分别占 6 0 %、17.6 %、11%、6 .5%和 4 %。

The Hexi mountain oasis desert area consists of three geographical areas: the forest grassland area on the northern slope of the middle part of the Qilian Mountain Range, the Zhangye desert oasis area and the Dongdashan Mountain forest grassland area. The altitude varies between 1 450 m to 4 200 m and the changes in the climate have shown a trend of decreased annual mean temperature and increased precipitation through the past 50 years. In accordance with this climatic trend, the glacies in the Qilian Mountains would be expected to have some steady development. Also, the volume of discharge of the Heihe River has been highly correlated with the changes in the climate. The major types of native vegetation include Reaumuria desert, mountain desert grassland, grassland, cold temperate coniferous forest, highland bush and alluvial communities, with 1 064 vascular plant species identified. The vegetation in the Qilian Mountains and that in the Dongdashan Mountains can be classified into a same floristic area that is younger than the Zhangye desert oasis area. Among the native plants hemicryptophytes make up 60%, phanerophytes 17.6%, therophytes 11%, cryptophytes 6.5% and chamaephytes 4%, and their distribution is highly dependent on the altitude.