Characterizing land condition variability in Northern China from 1982 to 2011

For the last three decades, Northern China has been considered as one of the most sensitive areas regarding global environmental change. The integration of AVHRR GIMMS and MODIS NDVI data (1982-2011), of which for the overlapping period of 2000-2006 show good consistency, were used for characterizing land condition variability. The trends of standardized annually ΣNDVI, temperature, precipitation and PDSI were obtained using a linear regression model. The results showed that Northern China has a general increase in greenness for the period 1982-2011 (a = 0.05). Also, annually ΣNDVI is significantly correlated with temperature and precipitation data at the regional scale (p < 0.05), implying that temperature and precipitation are the dominant limiting factors for vegetation growth. Since the greening is not uniform, factors other than temperature and precipitation may contribute to greening in some areas, while the grassland and cropland ecosystem are becoming increasingly vulnerable to drought. The results of trend analysis indicate that greenness seems to be evident in most of the study areas.