西藏日喀则江当及其毗邻地区植被组成特点

THE CHARACTERISTICS OF THE VEGETATION COMPOSITION OF JIANGDANG AND ITS ADJACENT AREA AT RIGAZE COUNTY IN TIBET

西藏河谷风沙地貌最为发育的日喀则宽谷段及其毗邻山地植被的植物区系组成表现为日益旱化和寒化过程中发生的温性中旱生、旱中生植物为主，带有北温带区系成份性质。由于区系发展的时间短，属的分化显得微弱，形成许多寡种、属的科。其植被受基质及水热条件再分配的影响表现为明显的垂直性分异。以上述分析为基础。

Aeolian geomorphy is most developed in Rigaze wide valley.The flora of this area and its adjacent mountain area mainly consists of temperate meso xerophytes and xero mesophytes subjected to strengthening drought and frigidity. The flora has the vegetational characters of the north temperate zone. Due to the shorter time of the flora development, the differentiation of genus is not striking and there are a lot of families with only fewer genera and species. There, vertical segregation becomes an important aspect of the vegetational characters because of the different medium and the reallocation of water and heat. On the basis of the above points, the characters of the psammophytic vegetation mainly composed of Sophora morrcroftiana is discussed specially.