Abstract: Based on the 1982-2006 normalized difference vegetation index (NDVI) and meteorological dataset of Southwest China, and by using ANUSPLIN, ArcGIS, and SPSS software, this paper analyzed the seasonal and annual variations of six shrubs’ NDVI and their correlations with climatic factors in the area. In the past 25 years, the annual average NDVI of three subalpine shrubs at high altitude (subalpine needle-leaf evergreen shrubs, subalpine broadleaf deciduous shrubs, and subalpine sclerophylla broadleaf evergreen shrubs) increased significantly, whereas that of the other three shrubs at mid and low altitudes (deciduous shrubs in temperate zone, evergreen xeromorphic succulent thorny shrubs in subtropical and tropical zones, and broadleaf evergreen and deciduous shrubs in subtropical and tropical zones) had less increase.The mean annual air temperature in the six shrubs except the evergreen xeromorphic succulent thorny shrubs in subtropical and tropical zones had a significant increase, and the mean annual precipitation presented an increasing trend in subalpine needle-leaf evergreen shrubs but a decreasing trend in the other five shrubs, reached a significant level in the deciduous shrubs in temperate zone. In the three subalpine shrubs at high altitude, the monthly NDVI was significantly positively correlated with mean monthly air temperature and monthly precipitation, and the correlations with the previous month’s mean air temperature and precipitation were the highest, showing a remarkable lag effect. For the other three shrubs at mid and low altitudes, the correlations of NDVI with air temperature and precipitation decreased obviously. At the high altitude, climate warming caused an increase of mean annual NDVI, suggesting that air temperature was the driving factor of the annual NDVI variation of the three subalpine shrubs. At the mid and low altitudes, the significant increase of air temperature didn’t cause a significant increase of NDVI.

Key words: Soil nitrogen, Nitrogen cycle, Model, Simulation