Spatial and Temporal Variations of Vegetation Belts and Vegetation Cover Degrees in Inner Mongolia from 1982 to 2003

The Normalized Difference Vegetation Index (NDVI) data in Inner Mongolia during 1982 to 2003 were used to classify the vegetation belts in four time periods and reveal spatial shifts of the vegetation belts between two sequential periods. Then, we analyzed the spatial and temporal variations of the vegetation cover degree and its relation to thermal-moisture factors taking the tpical steppe belt as an example. During the study period, the area of the typical steppe belt showed an increscent tendency, whereas the area of the desert steppe belt indicated a decreasing tendency. Otherwise, areas of the forest belt, the forest steppe belt and the desert belt did not represent any apparent tendency. Generally speaking, an evolution succession of vegetation belts was dominant during period 1 (1982-1987) to period 2 (1988-1992), whereas a degradation succession of vegetation belts (following succession orders of forest→forest steppe→typical steppe→desert steppe→desert) was dominant during period 3 (1993-1998) to period 4 (1999-2003). In between, evolution and degradation successions of vegetation belts were counterbalanced during period 2 (1988-1992) to period 3 (1993-1998). A significantly positive correlation appeared in the western part of the Xilingol Tableland and the Ulanqab Tableland. In contrast to precipitation, the correlation between the vegetation cover degree increment and air temperature was less significant. From 1982 to 2003, areas with decreasing and increasing linear trends of the annual maximum vegetation cover degree accounted for 52.6% and 47.4% of the entire Inner Mongolia, respectively, of which significantly decreasing trends appeared at the western edge of the Hulun Buir Tableland and the both sides of the Da Hinggan Mountains.