Spatial and temporal characteristics of grassland degradation in theriverhead area of the Yellow River

摘要

With the support of MSS images of the middle and late 1970s, TM images of the early 1990s and TMJETM images of 2004, grassland degradation in the riverhead area of the Yellow River was investigated. The spatial and temporal characteristics of the grassland degradation were analyzed. The results showed that the grassland degradation patterns were formed basically in the middle and late 1970s. The grassland degradation is obviously characterized by fragmentation, coverage decrease, swamp meadow drying, sandification and salification. The spatial heterogeneity of the type and degree of grassland degradation was significant. Sandification and salification mainly occurred in north-western alpine steppe, coverage decrease mainly in north central alpine steppe, and fragmentation and coverage decrease mainly in south-western alpine meadow. The grassland degradation is a continuous change process which has a large influenced area and is in a long-term scale. Slight and moderate degradation are more common, while serious degradation only occurs in some local regions. Moderate and serious degradation tend to increase since mid and late 1970s. Large-scale and moderate-degree degradation and desertification are generally typical characteristics of the grassland degradation in the riverhead area of the Yellow River.