Spatial and temporal pattern of alpine grassland condition and its response to human activities in Northern Tibet, China

Abstract

The trend in condition of alpine grasslands from 1981 to 2004 in different topographic regions and with different intensities of human activity in Northern Tibet was analysed by using remote sensing data and geographic information system techniques. The results of this study showed that the condition of the alpine grasslands in 2004 varied throughout Northern Tibet. The changes in condition over this period of most of the alpine grasslands (76.7%) were without any significant trend, whereas a larger portion of the remaining area showed significant recovery then underwent significant degradation. Where significant degradation did occur it was mostly on the steeper slopes whereas significant recovery was mostly on the flatter areas (<1° slope). As a result of strong solar radiation, high temperature, drying effects and more grazing activities, alpine grasslands on the sunny slopes had a greater potential for degradation. The special geographic location of Northern Tibet (with an average elevation of 4500 m.a.s.l.) means that alpine grasslands are mostly confined to an elevation ranging from 4500 to 5500 m, where both human and grazing activities were mostly migratory from 1981 to 2004. As a result, by far the majority of the alpine grasslands (90.4%) had either no significant degradation or some or significant recovery between 1981 and 2004. A greater proportion of alpine grasslands at high elevations (above 5000 m) had a significant trend of degradation than at lower elevations. The negative impact of residential areas on alpine grassland condition was smaller than that of roads.