Changes trend of terrestrial vegetation greenness period during recent 10 years in Songnen Plain

Based on GIS spatial analysis, the NDVI timeseries data of different vegetation types in northeast China were extracted by using the NDVI data from 1998 to 2008. Meanwhile, the phenological phases of vegetation types were simulated by Logistic function with their variation trends in 1998-2008. Results showed that 1) in 10 years, the date of vegetation beginning to grow was stable in Songnen Plain, and the growth trend in the local area was earlier than normal with a more than tendays value; 2) in the study area, the vegetation final date delayed evidently with a threeday average scale; 3) in a word, the change trend of vegetation grown season in Songnen Plain fluctuates between 2 and 3 days.