Spatial and temporal change of vegetation in growing seasons in Hebei Province based on SPOTVGT NDVI

SPOT-VGT NDVI datasets were used to analyze spatial and temporal changes of NDVI in vegetation growing seasons from 1998 to 2012 in Hebei Province, China. Vegetation types were come from MODIS product MCD12Q1 in 2004. The slope of liner regression equation was used to analyze the change trend of NDVI. The results showed that NDVIs in vegetation growing seasons showed a trend of fluctuating increase from 1998 to 2012. The lowest annual average NDVI in growing seasons was 0.49 in 1999, and the highest NDVI was 0.59 in 2012. The Pearson correlation coefficient (r) between annual average NDVI and mean precipitation was 0.893, the average NDVIs were related to precipitation more closely than to air temperature. The spatial distribution of NDVI in Hebei Province presented a trend of decrease from middle area to both sides. There were two areas with high NDVI values and two areas with low NDVI values. The highest average NDVI value 0.77 appeared in the southeast of Yanshan Mountains, especially near Wuling Mountain. The lowest NDVI value 0.01 appeared in the eastern coast of Hebei Province. Broadleaf forest had the highest average NDVI value 0.68 in growing seasons, followed by shrubland with NDVI value 0.64. The lowest NDVI 0.13 was in sparsely vegetated land or wetlands. The area of NDVI decrease in vegetation growing season accounted for 9.16%, while that of NDVI increase accounted for 90.84%, indicating that NDVI showed an increasing trend from 1998 to 2012. The areas with rapid NDVI increase were distributed in farming land of North China Plain, Taihang and Yanshan Mountainous regions. The areas with rapid NDVI decrease were mainly distributed in Bashang Plateau region, Beijing-Tianjin-Tangshan cities belt, Shijiazhuang, Xingtai and Handan cities, indicating that vegetation in these regions presented a trend of deterioration. The reasons were also analyzed.