Monitoring phenological key stages of winter wheat basing on temporal series of EVI data in Anhui China

Abstract

As an important factor during crop growing period, phenological stages is widely used in growing monitoring, field management and output forecasting. Temporal series MOD09A1, the 8-day reflectivity composite productions provided by NASA, which derived from TERRA/MODIS(Moderate Resolution Imaging Speetroradiometer) images from October in 2007 to June in 2008 were used to calculate enhanced vegetation index(EVI). Based on winter wheat's whole growing stages, four key phenological stages were defined from temporal series EVI as following: seedling stage, greenup, heading stage and maturity, then the spatial-temporal distribution of four phenological key stages were researched. The statistic temporal scale (a period of ten days) monitoring on ground has different with EVI temporal scale (8d) for winter wheat growth period, but they have better coincidences in seedling stage, greenup, heading stage and maturity. The seedling stage was from last ten-days of October to first ten-days of November, the greenup was from the middle ten-days to last of February of the next year, the heading stage was from the first ten-days to middle of April and the maturity was from the last ten-days of May to first ten-days of June. From the south to the north, with the increasing of latitude, the difference of every phenological key stage was not very obvious in winter wheat planting areas in Anhui Province. Only the maturity of samples in north of Anhui Province were postponed for about 8d. From the east to the west, with the decreasing of longitude, the greenup and maturity stage were postponed for about 8d in winter wheat planting area in Anhui Province and the seedling stage and heading stage have not obvious difference. On the whole, spatial distribution of phenological key stages of winter wheat is monitored and precision and accuracy of agricultural monitoring is improved basing on temporal series of EVI data.