Research on the Relationship Between the Spatial and Temporal Variation of Greenup and Precipitation in Mongolian Plateau

The Mongolian Plateau is located in the hinterland of Eurasia with sensitive climate and fragile ecology. The change of precipitation has obvious effects on the plateau vegetation greenup, which affects the plateau agriculture and animal husbandry production and the stability of the ecosystem. NDVI and TRMM data were used to analyze the relationship between greenup and precipitation factors in the plateau. The results were as follows: (1)The greenup of the plateau began from the pastoral area, and then was the forest area and the agricultural area. The grassland of Mongolia had the delayed trend, while the pastoral area of Inner Mongolia showed an advance trend; (2) The rainy season moved from northeast towards southwest, and the spatial consistency between the initial date of rainy season and the greenup was relatively strong; (3) The average annual precipitation of the plateau decreased from northeast to southwest. The precipitation of forest region and agricultural area increased obviously, the increase range of pastoral area was small, but the precipitation of Gobi region was decreasing. (4) The correlation between the greenup and precipitation factors shows that: in agricultural area, the main limiting factor for greenup was annual precipitation. For the forest area, it was the initial date of the rainy season. In the pastoral area, greenup date was controlled by two factors simultaneously, and it was more closely related to the initial date of the rainy season.