Evaluating the growth basal area method as a tool for estimating site productivity in uneven-aged ponderosa pine stands

The move toward ecosystem management requires foresters to manage for a diversity of forest structures, including uneven-aged stands.There are numerous knowledge gaps in the science of uneven-aged management.This has become evident in the area of estimating potential site produQtivity.There are many methods of appraising "site quality," but all fall short in uneven-aged conditions.Foresters need a method of estimating site quality in uneven-aged stands that is both dependable and practical.This study evaluated the Growth Basal Area method and variations thereof for estimating site productivity in uneven-aged stands.The GBA method has been used successfully in even-aged stands, and may have potential for application in uneven-aged stands.Numerous amendments and extensions of the GBA concept were explored including basal area and sapwood area as density measures, and fixed-and variable-radius plot estimates of competition around the subject tree.Hall's GBA approach was applied and amendments explored in eight uneven-aged ponderosa pine stands across Montana.The results suggest that Hall's method may not apply well in uneven-aged stands.There is a lack of evidence to support the strong relationship Hall found between GBA tree growth and surrounding density estimates.Amendments to Hall's method indicate that variable-radius plots may be more effective than fixed-radius plots for estimating the density of competition around GBA trees.Results also indicated that sapwood area density measures may be no more helpful than basal area measures, within Hall's approach.The variable of GBA tree sapwood area provided the greatest correlation with GBA tree basal area increment, and is recommended for consideration in future models.This study suggests that until uneven-aged stand dynamics are better quantified.Hall's approach has marginal utility in uneven-aged ponderosa pine stands.Milner.Kelsey helped with all my mensurational questions and gave important directions.Patterson, most importantly, bolstered my statistical background.Others outside the university also provided their time to this project.Jim Menakis aided with my core readings at the Missoula Fire Lab. Bob Wheeler provided necessary information regarding eastern Montana plots.Steve Slaughter pointed me in the direction of uneven-aged stands in the Clark Fork valley.Numerous graduate students provided information and assistance in this project.Foremost, I would like to thank Sandy Kollenburg who helped with increment and sapwood readings.Dean Coble aided with my statistical questions.Narayanan Valappil directed me to potential sampling sites.I would like to thank undergraduates who spent their weekends helping me in the field.Mike Reichenberg spent days coring in snow, rain, and sunshine.I can attribute my success in the field to his very aid.I would also extend thanks to Ann Lydiard who helped collect data at ninemile.And last but not least.Kirk Forsyth who also helped me collect data.Finally, I would like to