Vegetation of Qinghai Hoh Xil Region
Chin J Plan Ecolo. 1993, 17 (2):
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Qinghai Hoh Xil region is situated in the central part of the Qinghai-Xizang (Tibetan) Platean, the western side of the Qinghai-Xizang Highway between the Kunlun Mountains in north and the Tangkulashan Mountains in south (about 33˚52′—36˚16′ N lat.; 89˚24′—94˚04′ E long.). It is more than 80000km in size and the average altitude is as high as 4600—5000m while some peaks over 6000m. Most of this region is depopulateted because of its extreme elevation harsh climate, short growth period of forage grasses and difficulty for traffic. The mean temperature is lower than -5℃ in the whole year and lower than 6℃ in the hottest month, lower than -16—20℃ in the coldest month in most of areas of this region. The growing season of forage grasses is shorter than 100 days. The mean annual precipitation is relatively abundant with about 240--300mm in the eastern part and gradually reduced towards the northwest. About 69% of the total precipition falls in the three wormest months (June—Auguest) when plants grow. Soil is usually rough for its strong physicla effects and also week in biological effects. About 200 seed-plant species of 73 genera of 29 families have been noted in this region. Daisy family(Compositae), grass family (Gramineae),cabbage family (Cruciferae), and pea family. (Leguminosae) are the four richest species families. Families of grass, sedge (Cyperaceae), pea and daisy are the four most important ones in regetation composition. Stipa, Littledalea, Kobresia, Carex, Astragalus, Oxytropis, and Saussurea etc. are the most important genera. Almost 79% species are of Qinghai-Xizang Plateau geographic elements. About 69% species are hemicryptophytes the most adaptable lifeform to this kind of climate.Alpine steppe, Alpine meadow and alpine sparse vegetation are the main vegetation types. They occupy 51%, 14% and 26% of the total area respectively. Other types such as cushion vegetation, alpine desert, prostrate scrub etc. are also found. Generally the alpine steppe is distributed in the central part of the region, while the alpine meadow in the southeast and the alpine sparse vegetation in the northwest. This pattern of vegetation distribution is determined by the climatic factors. But vegetation distribution in some places is strongly affected by the following factors: landform, soil physical structure, soil moisture and soil salinity etc.