The goal of this project is to examine vegetation and landscape response to recent weather patterns in the Gila National Forest of New Mexico, a remote and undeveloped forest in the southwestern U.S. Although parts of the Forest have recently received substantial rainfall, like much of the western United States, the southwestern region of New Mexico has been experiencing drought conditions, particularly over the last decade. Four MODIS-Terra images were obtained in total, at two different resolutions (250m and 1000m) and on two separate dates (June 2002 and June 2004). Analysis focused on the MODIS 16-day composite Normalized Difference Vegetation Index (NDVI) product. The NDVI is a simple, well-known, and reasonable proxy for evaluating on-the-ground conditions through change in vegetation type and/or robustness. Elevation and land cover classification data were obtained from the U.S. Geological Survey (USGS). Long-term normals and annual averages for precipitation, temperature, and streamflow data were obtained for weather and stream discharge stations proximate to the Gila National Forest.
The percent change in NDVI between 2002 and 2004 was positive for all land classes, indicating that vegetation fared better in 2004 than 2002. Precipitation records showed that 2002 was a very dry year, while 2004 was anomalously wet, particularly early in the year. A transect generated to evaluate the relationship between change and elevation demonstrated that below 2000m a greater NDVI value was consistently recorded in 2004 than in 2002. The combination of satellite imagery and on-the-ground weather data supported the assessment of the immediate and longer-term effects of temperature and precipitation patterns on the natural resources of the Gila National Forest.