青藏高原扇穗茅高寒草原的基本特点

 扇穗茅(Littledalea racemosa)是青藏高原特有的疏丛短根茎禾草，主要生长在昆仑山以南的高原东北部的高寒草原带到高寒灌丛草甸带。它耐寒、耐贫瘠，水分生态适应幅度较广。扇穗茅草原是中国科学院、青海省可可西里综合科学考察队1990年考察后首次报道的一个高原特有的高寒草原群系。它主要分布在青海西南部的昆仑山以南、沱沱河以北、乌兰乌拉山和可可西里山以东地区。其群落的种类组成比较简单，约40余种。植物区系地理成分以青藏高原成分占优势，还有中亚成分和北温带成分。生活型组成以地面芽植物为主，一年生植物仅记录到一种，没有高位芽植物。植物生态类型全部是适应高寒气候生长的植物，水分生态类型以寒旱生植物为主，其次为寒中旱生植物。群落结构随环境条件的变化而有较大的差异。群落盖度一般在8月中旬最高，约为10—34%，扇穗茅一般占1／3以上。 扇穗茅草原是青藏高原有蹄类动物，如野牦牛、藏野驴、藏羚等国家一类珍稀野生保护动物和盘羊等二类珍稀野生保护动物的重要活动场所之一，对于这些动物的生存具有重要的意义。

MAIN CHARACTERISTICS OF LITTLEDALEA RACEMOSA ALPINE STEPPE IN QINGHAI XIZANG(TIBET)PLATEAU

Littledalea racemosa is one of the endemic grass species distributed only in the Qinghai- Xizang Plateau. and mainly within the alpine beIt between 4400- 4900m above sea level. The distribution area of the alpine steppe dominated or co- dominated by L. racemosa is delineated by the Kunlun Mountains in the north. the Tuotu- ohe river in the south. and the Hoh xil Mountains in the west.The steppe community is relatively poor in species. only 34 species being recorded in the 8 investigated plots.The 61.8%of the species are of Qinghai-Xizang Plateau geographic elements. and more than half (also 61.8%)of species belongs to the hemicryptophytes.Most of species are perennial with exceptions of 2 prostrate shrubs and I annual. Based on the species composition and structure of the investigated com- munities. at least 4 community- types of the alpine steppe were distingui- shed.they were the L. racemosa dominated steppe. the L. raccmosa and Carcx moorcrojtii co- dominated steppe. the L. racemosa and Astragalus conf- ertus(A. polycladus)c0-dominated steppe. and the L. racemosa and Stipa purpurea co- dominated steppe. The difference of soil texture and structure were the principal reason for formation of these community-types.