Grasslands Ecological Monitoring System (GEMS)

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Sentinel Network for Trend Detection

The differences in the seasonality of vegetation across the Great Plains reflect differences in land use and land cover. This image displays three MODIS Aqua NDVI scenes from 2003. Red is 25 May. Green is 12 July. Blue is 07 April. If an area has high NDVI at each date, then the area appears whitish. If an area has high NDVI only during one of the dates, then the area appears in purer tint of red, green, or blue. For example, the extensive bright green areas correspond to summer row crops (corn, soybean, spring wheat) that do not yet have a dense plant canopy by the end of May. Similarly, the blue regions across Kansas and Oklahoma correspond to areas of extensive winter wheat cultivation. The Badlands of South Dakota appear black because there is very little vegetation cover at any of the three dates. Blended colors correspond to significant vegetation cover at two of the three dates. For example, the tallgrass prairie of the Flint Hills in eastern Kansas and Osage Hills in northeastern Oklahoma appear as an orangish thumb. The network of sentinel stations are represented by the white circles across the three-state region.

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