THEMATIC MAPPER CHARACTERIZATION OF LODGEPOLE PINE SERAL STAGES IN YELLOWSTONE-NATIONAL-PARK, USA

Landsat Thematic Mapper multispectral data were used to identify the s pectral reflectance characteristics of Yellowstone lodgepole pine (Pin us contorta var latifolia) successional stages, and to examine the rel ationships between spectral and biophysical factors. Ten spectrally de fined forest cover types were created from unsupervised classification of the Landsat TM data, using a geographic information system to rest rict data analysis to areas of similar slope, elevation, and surficial geology within the Central Plateau region of the park. Biotic data on forest overstory and understory conditions were collected from 69 sam ple sites within the 10 spectral cover classes. Field data were used t o regroup the 69 sites into six biotically and spectrally distinct cov er types, ranging from early postfire regeneration (LPO) to late-stage (LP3) subalpine fir succession. Increased absorption in the visible ( TM 1, 2, and 3) and middle-infrared (TM 5 and 7) bands were related to the age and development of a stand. Changes in absorption were rapid during the initial stages of stand regeneration, but the rate of chang e slowed as stands progressed into later successional stages. Biotic f actors relating to the physical structure of the forest canopy (height , basal area, biomass, and LAI) are cor-related with the visible and m iddle-infrared bands of the Thematic Mapper. Understory factors were p oorly correlated with spectral response, except soil and fireweed, whi ch are dominant early in succession, but rapidly decrease in Later sta ges. The spectral reflectance of a successional forest stand over time is a function of the combined effects of the overstory canopy, the am ount of shadow within a canopy, and the condition of the forest unders tory As a forest develops from a disturbance to old-growth, the spectr al response of a stand progresses along a vector or vectors linking th e three factors. Spectral response changes are nonlinear with respect to time, as large-magnitude changes are observed in the first 20-30 ye ars following a disturbance, and the rate of change lessens as forests develop into old-growth.