Document Actions

Vegetation Monitoring and Decision Support

Ground-based vegetation monitoring presents some practical challenges to natural resource managers tasked with assessing vegetation dynamics across large areas through time. Information obtained from ground-based techniques can be enhanced through frequent, synoptic observations made from satellite sensors. Since 1989, the USGS/EROS Data Center (EDC) has been deriving an index of vegetation greenness from 1km satellite imagery commonly used in phenology studies, the normalized difference vegetation index (NDVI). Through NASA/Raytheon sponsorship, the University of Arizona has partnered with natural resource managers to make these data operationally accessible online. The resulting “RangeView” website empowers a user to zoom in anywhere in the conterminous U.S., northern Mexico and southern Canada, and run a time series animation of NDVI for any sequence from 1989 to the current period. It also permits side-by-side comparisons of different periods and relative greenness products (e.g. difference from average). Recent advancements include a new sensor which includes images of 250m resolution since 2001 which RangeView has been able to provide on-line for the southwestern U.S.

Aspen Fire Time Series Images

The power of the RangeView web site lies in providing the user spatially explicit information on vegetation greenness using biweekly satellite images. Visualizing spatial and temporal vegetation changes in response to climate or disturbances, such as wildfire, helps illustrate the value of frequent imagery to natural resource managers. Arizona's largest wildfire in June 2003 occurred on Mount Lemmon, north of Tucson. The Aspen Fire burned a total of 84,750 acres west and north of Mt Lemmon highway. A year before the Bullock Fire claimed 30,563 acres east of the highway and the Oracle Hill fire burned 2,432 acres just north of Mt. Lemmon. The images below show the Mt Lemmon prior to the Aspen Fire beginning on June 9, 2003 – all but where the Bullock and Oracle Hill fires burned the year before are deep green. In the middle images a decline in vegetation greenness is evident (and there are white areas where smoke and clouds prevailed over the 16 day composite image). The images on the bottom (July 27 and then September 13), the fire perimeter is clearly visible – much less green than prior to the fire.

MODIS NDVI 250m Images