Lecture Notes – Vegetation indices Fred Watson, ENVS 436/536, CSUMB, Fall 2010 Many of these slides are from Jianglong Zhang and Cindy Schmidt

Vegetation Indices Highlights subtle variations in the spectral responses of vegetation: –Reflects strongly in near IR; absorbs strongly in red –Can discriminate between healthy and stressed vegetation pre-visually Image via Zhang

(Some) Vegetation Indices Ratio Vegetation Index: NIR/Red –Range: 0 (bare soil) to >20 (dense vegetation) –Sensitive to variations in dense canopies –Rarely used Normalized Difference Vegetation Index: NDVI = ( NIR – Red ) / ( NIR + Red ) Range: -1 (bare soil) to 1 (dense vegetation) Sensitive to low levels of vegetation cover Compensates for unwanted variation due to changes in illumination etc. Very common Slide via Zhang

Vegetation Indices Image via Zhang

Here’s a video of NDVI changing across the lower 48 states: Link via Zhang

Image via Zhang

Image Ratioing Benefit: –Looking at relative brightness values, not absolute so radiometric errors are reduced. Ex: absolute reflectance values for forested areas may vary depending on orientation relative to sun illumination; however the ratio of the reflectance values should be similar. Slide via Zhang

Landsat TM image NDVI image Slide via Zhang

Study of Yellowstone meadow phenology lead by Watson, Thein, et al. (start by showing video)

EcoViz: Yellowstone Ecosystem Science and Visualization Meadow phenology survey

MODIS phenology

Forest cover survey

Leaf Area & Water versus Forest Age