[Correlation analysis of regional vegetation seasonal fluctuation and climate factors based on MODIS-EVI]

Taking Zhejiang Province as study area, and based on the data of MODIS-EVI, daily mean air temperature and daily precipitation from 52 weather stations, and actual land use in 2001-2004, the time lag cross-correlation analysis was made to relate the seasonal fluctuations of enhanced vegetation index (EVI) of farmland, woodland and garden plot with air temperature and precipitation. The results indicated that in most areas of Zhejiang, EVI had no time lag to air temperature, but about one month lag to precipitation. The time that air temperature or precipitation significantly influenced the seasonal fluctuation of most areas EVI lasted about 50 days. The correlation coefficients of the EVI of farmland, woodland and garden plot with air temperature and precipitation differed with time lags. When the time lag was zero, the correlation coefficient decreased in the sequence of woodland > garden plot > farmland, and when the time lag was not zero, it changed in adverse. The EVI of these three land-use types all had stronger correlation with air temperature than with precipitation, indicating that air temperature had more influence on the seasonal fluctuation of EVI.