Fall colors

Fall colors
Trees in Simpson Plaza, UW Campus - Oct 11, 2013 (photo: Ramesh Sivanpillai)

Friday, December 5, 2014

Monitoring the Phenology of Quaking Aspen at UW

-- Parmeshwor Aryal, Gregory F. Galli, and Jacob A. Rohrer

Plant response to seasonal change varies based on type of plant species and the growth stage. The Normalized Difference Vegetation Index (NDVI) has been predominantly used to determine the effects of environmental conditions on vegetation performance and their phenological changes over the growing season. A study was conducted to understand the phenology of quaking aspen (Populus tremuloides Michx.) in response to the seasonal environmental changes.

Spectral reflectance values of adaxial (top) and abaxial (bottom) foliar surface of a young quaking aspen tree were obtained and NDVI values were calculated for both surfaces from early fall (September 11, 2014) to late fall (October 21, 2014).

Phenological changes in a quaking aspen from September 11 to October 21, 2014

As the fall season progressed into winter, the NDVI values of both surface of leaf decreased over the time which was congruent with the visual changes in leaf color. The NDVI values of adaxial surface was found to be higher than that of abaxial surface. That suggested that the NDVI is effective indicator for phenological changes during growing season and for determining different reflectance between two sides of the leaves.

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