Old-Growth Ponderosa Pine from Succession In Pine-Bunchgrass Forests In Arizona and New Mexico

The growing understanding of the importance of landscape diversity has led forest managers to anticipate the need to maintain or create old-growth ponderosa pine stands in the southwest United States. Recurrent low intensity fires were historically part of the process that created and sustained old growth. Succession is described for Pinus ponderosa/Festuca arizonica, P. ponderosa/Muhlenbergia virescens, P. ponderosa/Muhlenbergia montana, and Pseudotsuga menziesii/Festuca arizonica habitat types. These environments all have similar fire histories, grassy understories, and oldgrowth Pinus ponderosa in late successional and climax stages. Eleven stages of succession are described and the role of fire is enumerated. Stages 8,9, and 10 are old growth, the features of which begin to develop at about 200 years (age of oldest trees at breast height) but are best expressed after about 300 years. Fire is important within early stages to direct succession to an old-growth objective. Recurrent fires are needed to maintain quality old growth and to lessen the probability of a stand-replacing catastrophic fire. Fire management within old-growth reserves could be applied to the Monument Canyon and G. A. Pearson research natural areas as well as wilderness areas, national parks, and forest districts where planned landscape diversity includes an old-growth allocation.