Grassland Cover Change near the Source of the Yellow River:Case Study of Madoi County,Qinghai Province

Grassland is the main cover type in the region which includes the source of the Yellow River.There are many studies on grassland in this area,but most of them use data from after the 1980s,and are not comprehensive.The data used in this research is from the 1970s,so reflects the situation from an earlier time period.We used remote sensing images from 1977,1990 and 2003 for the interpretation of land cover in Madoi County in Qinghai Province.As other research has shown,the degradation of grassland is mainly due to changes from grassland to other land use types,but there also other types of changes such as fragmentation and decreased coverage.We first used the classification system for grass cover change,and then through the comparison of remote sensing images from different time periods,the grass cover change is clearly described and we calculated statistical data on grass cover change in Madoi County.The grass degradation area of each type and degradation degree of each level was derived from analysis of the interpretation results.The temporal and spatial characteristics of grass cover change were obtained and analyzed in terms of elevation,slope,and aspect characteristics.The results show that the grass degradation pattern of Madoi County was already formed in the 1970s and degradation has continued since then,becoming serious after the 1990s.The grass cover change in Madoi County is mostly lightly or moderately degraded,and the main type of grass cover change in Madoi County is fragmentation or decreased coverage.Changes in grass cover were mostly between the elevation of 4200 meters and 4700 meters,and concentrated on slopes between 0 and 15 degrees.There is no relationship between grass cover change and aspect.There are multiple causes of grass cover change in Madoi County,and quantitative analysis should be done to reveal the main factors causing the grass degradation patterns,to provide decision-making support for ecosystem restoration work.