干旱区生态环境知识资源中心

The Hindu Kush and Karakorum Range represent a traditional old pasture land in which Artemisia-dwarf shrubs are characteristic. To assess the grazing impact on the vegetation, six stands were selected, four in the area of Yasin (Gilgit district) and two in Phargam (Chitral district), along a gradient from 2600 in to 3600 in a.s.l. A total of 35 releves were defined and the vegetation was recorded sociologically. About 100 plant taxa were rated according to their morphological and functional features. Additionally, microclimatic and phytomass data were collected.

Three types of "steppes" were distinguished within the wide Artemisia vegetation belt: (1) The open semi-desert-steppe is rich in ephemerals and ruderal strategists. Perennial plants are dense, small leafed, hairy and sometimes thorny species. The productivity of phytomass is very low, 70 % being located underground. (2) The more mesophilous Artemisia persica-steppe the total cover reaches 30 % to 65 % depending on intensity of grazing. Apart from the overgrazed sites, in which Artemisia persica - a semi-woody chamaephyte - dominates, rhizomatous hemicryptophytes prevail. In the less grazed parts more shrubs and perennial grasses occur. (3) In the thorn cushion-steppe Acantholimon lycopodioides and A. kokadense are prominent. Many herbaceous species are flat, hairy and have a shoot basis covered with dead plant material. Stress-tolerant strategists and stress-tolerant competitive strategists prevail. Artemisia persica and the proportion of annuals decrease.

The most important mechanisms of settlement were found to be sexual reproduction by therophytes and the asexual and clonal reproduction by perennial herbs, grasses and sedges. Overgrazing inhibits these processes of potential recovery, enhancing desertification and transforming potential herb- and grass-rich steppes into monotonous Artemisia-steppes and semi-deserts.