Abstract

Landsat time series data sets were acquired for the Santa Fe National Forest in New Mexico. This area includes\rthe San Pedro Parks Wilderness area, which was designated as an official wilderness in 1964. Eight autumnal\rLandsat Thematic Mapper (TM) scenes acquired from 1988 to 2006 were analyzed to determine whether\rsignificant changes have occurred throughout the region during the past 18 years and, if so, to assess whether\rthe changes are long-term and gradual or short-term and abrupt. It was found that, starting in about 1995,\rmany of the conifer stands within the Wilderness area showed consistently gradual and marked increases in\rthe Shortwave Infrared/Near Infrared Index. These trends generally imply decreases in canopy greenness or\rincreases in mortality. Other high-elevation conifer forests located outside of the Wilderness area showed\rsimilar spectral trends, indicating that changes are potentially widespread. The spatial patterns of forest\rdamage as inferred from the image analyses were very similar to the general patterns of insect defoliation\rdamage mapped via aerial sketch mapping by the United States Department of Agriculture Forest Service\rForest Health Monitoring Program. A field visit indicated that zones of spectral change are associated with\rhigh levels of forest damage and mortality, likely caused by a combination of insects and drought. The study\rdemonstrates the effectiveness of using historical Landsat data for providing objective and consistent longterm\rassessments of the gradual ecosystem changes that are occurring within the western United States.