Applying spectral analysis and time series characteristics,the decision tree algorithm was put forward,which can extract the main fall crops effectively and easily.

Based on the historical climate data and spring phenological data in the same period from Tulufan and Shanshan station during 1980-2004,we statistically analyzed the change tendency of air temperature and spring phenology and their correlativity,the correlations of each phenology,and the influences of temperature change in different time interval on phenology.

(2)There is a high correlation between spring phenology and temperature,slight correlation between spring phenology and days of precipitation.

According to the phenological observation data of Shishahai Area in a time span of 13 years,by the method of plant phenological period frequency distribution pattern,the phenological season of Shishahai Area is divided.

Phenological observation data of plant communities from 1982 to 1996 at 5 sites and a method for phenological cumulative frequency modeling were used to determine the beginning dates of local phenological seasons and their corresponding threshold values of normalized difference vegetation index(NDVI) in each year.