Monitoring of Land Use in the Major Grain Crop Production Area Using Temporal Characteristics of Ndvi Obtained from Coarse Resolution Satellite Data

NDVI obtained from satellite at the pixel over the area of crop cultivation would represent a specific temporal profile, which could be discriminated from that of other land use. In this study, the author attempted to estimate the acreage of winter wheat sown area using multitemporal NDVI obtained from NOAA-AVHRR data. The study site was selected in the Huang-Huai-Hai plain in China, where the most popular cropping pattern was double cropping of winter wheat and maize. First, the author examined a linear unmixing method, of which the value of NDVI at pixel was assumed as a composition of end-member values of NDVI in proportion to land use components. This method could be adopted if there was a high spatial resolution data taken in the appropriate period to estimate end-member values, and could be applied to the area where cropping season was almost resonant in the wide area. Secondly, he examined a relation of the ratio of winter wheat sown area in a pixel from the values of 2-temporal NDVI, which could show the relation with the components of land use. Estimated acreage by the either method showed a compatible spatial distribution with the acreage obtained from LANDSAT-ETM+ data. The advantageous point of the second method was that it would not require a high spatial resolution data for each year, supposed that the consistent parameters were adopted. By applying this method, the author could characterize the recent changes of winter wheat sown area in the northern part of the Huang-Huai-Hai plain.