USING GENERAL LAND OFFICE RECORDS TO ASSESS FOREST SUCCESSION IN PONDEROSA PINE DOUGLAS-FIR FORESTS IN WESTERN MONTANA

Original (1901 and earlier) General Land Office (GLO) records were use d to quantify successional changes in Ponderosa Pine/Douglas-fir (Pinu s ponderosa/Pseudotsuga menziesii) forests in western Montana followin g altered fire regimes. GLO bearing tree data provided the means to re construct presettlement forest structure in the study area: the former Fort Missoula Timber Reserve (FMTR), located in Pattee Canyon near Mi ssoula, Montana. Tree importance values, tree density values and basal area values were estimated from the GLO survey notes and compared to forest data collected in 1992 to assess successional trends. The resul ts show that with reduced fire influence, Douglas-fir in FMTR has made major gains in stand dominance over ponderosa pine and western larch (Larix occidentalis), especially on north aspects; on south aspects, f ormer savanna and grassland communities have experienced conifer invas ions.