Monitoring Northeastern United States Forest Condition Using Landsat Data

The broad overviews obtained with Landsat data can provide information concerning the location, types, and magnitudes of forest changes not easily obtainable by other means. One of the main goals of the current study is to provide spatial information regarding the more subtle forms of forest change rather than those primarily related to land cover conversion. A forest-dominated area in northern Vermont was selected as the principal study area for this investigation. This region was the site of extensive field and remote sensing investigations of forest decline in the 1980s, when it was discovered that forest decline was pervasive at high elevations and that the declining conditions could be mapped and monitored using Landsat data. A pilot study was conducted to determine the nature and level of spectral changes that have taken place in these high-elevation forests since this time period. Datasets used included Landsat multispectral scanner (MSS) data acquired in 1976 and 1991, Landsat thematic mapper (TM) data acquired in 1991, and Landsat enhanced thematic mapper plus (ETM+) data acquired in 1999. After developing an approach that enabled forest spectral comparison across sensors, it was found that subtle forest changes have occurred throughout much of the region, with the most obvious changes having occurred at the higher elevations. Additional investigation is warranted to determine the reasons behind these subtle changes.