Temporal and spatial variations of EVI and its response to influence of climate with different grassland types in Xilin Gol League

MODIS/EVI data from 2000-2014 were combined using the Harmonic Analysis of NDVI Time-Series (HANTS) and Maximum Value Composites method (MVC) to investigate spatio-temporal variations of vegetation EVI and its climatic factors. Trend line and correlation analyses were used to examine Xilin Gol League Grassland from 2000 to 2014, providing a scientific basis for the protection of vegetation. Results showed that the EVI value of different vegetation increased after May, peaking in July or August. The Warm Grassland Desert, Warm Mountain Meadow, and Swamp vegetation showed a downward trend, while other vegetation types showed an upward trend. Vegetation in most parts of the Xilin Gol League had no significant changes in spatial pattern. It keeps an improved trend in the vegetation that the Warm Grassland, Warm Desert Grassland, Warm Meadow Grassland, Alpine Grassland and Warm Desert in the central, southern, southwestern Xilin Gol League, Erenhot, Sonid Left, East Ujimqin, and West Ujimqin. However, the vegetation in Low-salinity Meadow, Improved Grassland, and Warm Grassland Desert showed slowly decreasing trends in the northern, southern, and western parts of the Xilin Gol League. Vegetation EVI was mainly controlled by mean temperature, precipitation, mean relative humidity, and sunshine hours, which is affected by the average wind speed. Temperature was the most important factor affecting vegetation growth. The correlation between EVI and meteorological factors was high in Low-salinity Meadow, Improved Grassland, Warm Grassland, and Warm Desert Grassland and low in Alpine steppe. The improved area was larger than the degraded area in Xilin Gol, and vegetation was mainly controlled by temperature.