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WWETAC Focus Area: Landscapes

Schrader-Patton C, Grulke, N.E., Dressen M. E. 2016. Characterizing a forest insect outbreak in Colorado by using MODIS NDVI phenology data and aerial detection survey data. Gen. Tech. Rep. PNW-GTR-940e. Portland, OR: USDA Forest Service, Pacific Northwest Research Station. 35 p. TreeSearch link.

Satellite derived NDVI (normalized difference vegetation index) data at a resolution of 250 m were used to assess insect outbreak damage to forests on the Medicine Bow-Routt National Forest in Colorado. To translate the raster based information into a form useful to forest managers, maps were created that show intensity and time of insect disturbance, aggregated by forest stand polygon. Because NDVI loss is applied to forest stands, this reduction in greeness can be associated with stand species composition, canopy cover and tree size. This rapid assessment provides managers with a synoptic look at events such as insect outbreaks and droughts. Mortality patterns from these processes can help managers prioritize forest stand monitoring and salvage efforts.

Figure 3 (Left) from Schrader et al., 2016 (referenced above): (A) Sum of normalized difference vegetation index (NDVI) loss during the period 2001–2012 for FSVeg stands. Biennial NDVI loss pixel values were averaged for each stand and then summed over the six biennial periods. Nonforest and timber harvest areas are rendered in white. Class breaks were determined using the Jenks natural breaks algorithm; (B) total tree mortality as detected over the same period by aerial detection surveys.