Wu Z.,Chinese Academy of Sciences |
Wu Z.,State Key Laboratory of Environmental Protection Regional Ecological Processes and Functions Assessment |
Wu Z.,State Key Laboratory of Environmental Criteria and Risk Assessment |
Li F.,Chinese Academy of Sciences |
And 11 more authors.
Journal of Natural Disasters | Year: 2014
Based on existing studies, this study developed a method to estimate degraded grassland according to theoretical vegetation coverage extracted from remote sensing data. This method was applied to the case of the Three-river Headwaters Region in Qinghai Province of China using the decade data of Pathfinder NOAA AVHRR NDVI from 1981-2006, vegetation maps, soil maps, DEM and the meteorological data of growing season. The study area was first classified into 768 ecological units based on vegetation types, elevations, soil types, cumulative precipitation and accumulated temperatures of growing season with similar growing conditions within each ecological unit. Then, the maximum vegetation coverage value was assigned to corresponding ecological unit as the theoretical vegetation coverage. Finally, vegetation coverage of the other period was compared with the theoretical vegetation coverage to obtain the status of grassland degradation of that time. This method could solve the problem about lack of reference system and misuse of remote sensing data in large-scale grassland degradation evaluation in some extend. The results show that the pattern of degradation of grassland in the Three-River Headwaters Region had formed before 1980s and this pattern remained relatively stable during 1980s and 1990s. After 2000, the grass land degradation was preliminarily controlled, but the situation remains grim. Degrees of grassland degradation vary in different counties and the status of grassland degradation is more serious in western counties than in eastern counties. The results are agree with the status quo of the study area.