论世界芨芨草属(禾本科)的地理分布

本文详细讨论了世界芨芨草属的地理分布等问题。1．全世界芨芨草属共有23种1变种，分为5个组。本文对它们进行了系统介绍。2．属的地理分布，最北为北纬62°(羽茅、毛颖芨芨草)，最南为北纬26°(林阴芨芨草)。就海拔而论，分布最低的海拔记录为120m(雀麦芨芨草)，分布最高的海拔记录为4600m(干生芨芨草和藏芨芨草)。3．本文讨论了芨芨草属5个组(芨芨草组，钝基草组，直芒草组，新芨芨草组，拟芨芨草组)的系统位置，和每个组包括的种类及5个组的分布格局。4．根据塔赫他间世界植物区系区划，统计了每个区的种数，明显看出伊朗—土兰区种类(18／24)是第一位，东亚区(14／24)居第二位。中国有17种，横断山脉地区、华北地区和唐古特地区种数最丰富(10种和9种)。5．研究结果表明：(A)从种的分布格局分析可见，横断山脉地区北部、唐古特地区东部和华北地区西部的交汇地是芨芨草属分布中心。(B)根据芨芨草属形态特征演化趋势分析和地史学资料推测横断山脉地区北部是芨芨草属的起源地。(C)有三条路线向外散布:a)从横断山脉地区向西沿喜马拉雅山脉，经克什米尔地区抵达地中海和中欧；b)从横断山脉向西北经祁连山、天山、塔里木盆地西侧山地，抵吉尔吉斯斯坦伊塞克湖； c)由横断山脉向东北经甘肃、宁夏、陕西、山西、河北和东北，抵达西伯利亚，东达堪察加半岛，西至鄂毕河上游，并经白令海峡陆桥分布到美国内华达山脉和落基山山脉。(D)该属植物集中分布于北半球半湿润、半干旱和干旱地区，以及极端干旱的荒漠区山地。植物的形成、发展和生态适应与气候相联系，并经过长期的适应和进化，塑造了一系列中生、旱中生的形态－生态特征和生活型。

ON GEOGRAPHICAL DISTRIBUTION OF ACHNA-THERUM BEAUV.(GRAMINEAE)

In this paper the worldwide geographical distribution of the genus Achnatherum is discussed in detail. The paper is divided into following five parts: 1. Conspectus of taxo-nomic system: The genus Achnatherum Beauv. comprises 23 species, which can be grouped into 5 sections. The characteristics of each section are described. An infrageneric system including species in each section is presented. 2. Geographical distribution of the genus: The northernmost occurrence of the genus is represented by A. sibiricum and A. confusum at latitude 62 N and the southernmost by A. chingii var. laxum at latitude 26N. As far as vertical distribution is concerned, the lowermost record of latitude in the genus is at 120 m (represented by A. bromoides) and the highest record at 4600 m (by A. jacquemantii and A. duthiei). 3. Systematic position and geographical distribution of sections: The systematic position of five sections in the genus, i. e. , Sect. Achnatherum, Sect. Timouria, Sect. Aristella, Sect. Neotrinia and Sect. Achnatheropsis, species in each section, and the distribution pattern of each section are discussed. 4. Geographical distribution of species; According to Takhtajan's regionalization of the world flora, the number of species in each region is presented. The Irano-Turanian Region (18/24) comes to the first in number of species, followed by the Eastern Asian Region (14/24). Seventeen species have been found in China, where the Hengduan Mountain Region, Huabei Region and Tangut Region are the richest in species ( 10 species and 9 species, respectively). 5. Discussions and conclusions: (A) The analysis of distribution patterns of species shows that the centre of distribution of Achnatherum. is located in the boundering area of the Hengduan Mountain Region, Tangut Region and the Huabei Region. (B) Based on the analysis of evolutionary trends in morpho- logical characters of Achnatherum and geological evidence, it is presumed that this genus probably originated in north part of the Hengduan Mountain Region. (C) Three migration routes lead to the present distribution pattern;a) From the Hengduan Mountain westward a-long the Himalayas across Kashmir Region to the Mediterranean and Central Europe, b) From Hengduan Mountain northward across the Qilian Mountain, west of the Huanghe corridor, Tianshan Mountain, mountains west of the Tarim basin to the Issyk lake, c) From Hengduan Mountains northeastwards across Gansu, Ningxia, Shaanxi, Hebei, and northeast part of China to Siberia, eastwards to Kamchatka Peninsula, westwards to upper stream of the Ob River, and across the Asia-Bering Land Bridge to Nevada and Rocky Mountains in west United States. (D) The majority of species of Achnatherum are distributed in subhumid, semi-arid and arid areas,and also on mountains of extremely arid desert region in the Northern Hemisphere. A .Series of morphological- ecological characteristics of mesophytes and moderate xerophytes and life-form resulted from long-term adaptation and evolution.