Satellite Imagery Analyses of Seasonal Shifts of Vegetation Greenness at the Great Smoky Mountains National Park

Abstract

This study investigates the temporal shifts in seasonal vegetation coloration, focusing on changes in greenness levels (measured by NDVI) from 1982 to 2023, using multiple satellite sources including AVHRR, Landsat, MODIS, and VIIRS. The primary objectives of this research are twofold: (1) to determine whether greenness levels have significantly changed during spring and fall, and (2) to assess whether there are notable differences in NDVI values among the various imaging sensors used. Given the context of global warming, it is plausible that greenness levels would show an increase on the same date in early spring or late fall across multiple years. Our study area consists of the Great Smoky Mountains National Park, where we analyze the timing of seasonal changes, revealing a trend toward earlier springs and longer falls. Our findings indicate significant increases in NDVI values during spring across all datasets, notably from AVHRR and Landsat, while fall data shows less consistent trends, with MODIS and VIIRS revealing minimal changes.  The research highlights the importance of sensor selection in NDVI measurements, with non-parametric test results confirming significant variances among the sensors analyzed. This study contributes to understanding the implications of climate change on vegetation dynamics, underscoring the need for continued monitoring as seasonal patterns evolve.