Abstract:
Landsat Thematic Mapper (TM) imagery was used to analyze seasonal and interannual change of forest stands in Ft. Leavenworth, Kansas for the years 1987, 1988, 1990, and 1994. In preprocessing the scenes were haze corrected. Differential GPS coordinates taken in the field and points from paper maps were used in the resample. The area of study was isolated from all other areas with the use of ISOCLUST an unsupervised classification module. Boolean images were produced using RECLASS and the GROUP modules for the July scenes. The boolean images were multiplied by the normalized difference vegetation index (NDVI) values for analysis of the July scenes.
In the analysis of the July scenes, the July 1987 NDVI values had the highest mean. So the July 1987 boolean image was used as a mask for all the other images. The mask was
multiplied by the NDVI values for each of the scenes. The histogram statistics were analysis for each date.
The July 1987 mean NDVI value was the highest for all the dates. In visual analysis, July 1987 had the largest extent and the most vigorous vegetation of all the scenes. In visual analysis of the June, July, and October 1988 images the most vigorous vegetation was in valleys and low-lying areas reflecting the drought conditions of that year. However, the study-forest mean NDVI values for 1988 did not reflect a drought year. The mean NOVI values in July 1988 and July 1994 have comparable results with similar values. The lowest mean occurred in July 1990. Visual interpretation of July 1990 revealed a year of low vegetation vigor. This can reflect a lag in the health of leaves to drought conditions which started in 1988 and continued into 1989.
