| Abstract: | The steppe vegetation of the Xizang (Tibet) Plateau is somewhat similar to the temperate steppe of our country, but it possesses its own characteristics: 1. The elements of the Qinghai-Xizang floral region or plant species taking the Qinghai-Xizang Plateau as their chief distribution center play a dominant part in tile constitution of the steppe communities. In these communities, the plants are usually sparse and dwarf, their growth period is shorter and the biological productivity is lower than the steppe in the temperate zone. They possess synusia consisting of herbaceous plants fit for cold climate, synusia consisting of kobresia and synusia consisting of cushion plants. 2. There are 4 types of steppe vegetation in the Xizang Plateau. And the tussock-grass steppe is the most typical. According to their different ecological characteristics, they may be divided into 3 types. Of these, the most widely distributed type is the cold temperate-weak semiarid steppe. And there are many characteristical steppe communities. 3. Distributionally, the steppe in the Xizang Plateau belongs to a special type of vertical distribution in the subtropical latitude zone, it is different from the gene- rally known montane vertical belt, and possesses a vertical-horizontal distributive nature, i.e. "zonation of plateau". Within the Plateau steppe region, steppe eommunities with different ecological characteristics have clearly marked areal differentiaton, and which has determined the nature of the vertical belts in these areas. According to different basal belts of the vertical belt spectrum, such belts may be divided into 3 types. There are no forests in the montane vertical belt spectra in the Plateau steppe region, and the upper distributional limit of the steppe vegetation reaches an altitude of about 5200 (5400) m., which is the highest distributional limit of steppe on the earth. |
