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Plant phenology in mountainous areas follows elevation gradients, with spring green-up beginning in low elevations and increasing in elevation as the season progresses. This green-up is an important ecological event as studies have shown ungulates sync their spring migration to this green wave for maximum nutrition consumption at the beginning of the season. This correlation is useful when studying habitat use of ungulates. The current standard for tracking this green-up uses the normalized difference vegetation index, or NDVI. This index tracks changes in vegetation using satellite imaging every eight days and assigns a value on a greenness scale that correlates to the amount of green vegetation present at a scale of 6.25 ha. Vegetation change can be measured by the change in the values of the greenness scale over time. While this index is useful for studying large areas, its accuracy in spaces less than 6.25 ha is questioned. The goal of my research is to classify vegetation green-up using daily camera trap photos collected at 106 sites throughout a study area from March to July of 2019. This study area is in Spanish Fork Canyon in central Utah and includes elevations from 1,000 to 3,000 meters. The photos from these sites provide camera-based greenness values at ground level at a small spatial scale. Comparing the average rate of change in camera-based greenness values to the instantaneous rate of greenup (IRG) derived from NDVI data will show how accurate satellite-based indices for this area are. The purpose of this study is to track vegetation green-up in this area and investigate the accuracy of IRG by comparing it to camera-based greenness values that evaluate vegetation greenness on a much smaller scale.


Utah State University

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Life Sciences

Vegetation Green Up: Ground-Truthing NDVI Data Using Wildlife Cameras

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