Fire History of Walnut Canyon National Monument [draft]

Davis, Kathy

This report documents f ire history of Walnut Canyon National Monument. Analysis of fire scar and age class of conifer regenera t ion provided data for the ponderosa pine forest. Primary attention was given to frequency, spread, behavior, relative intensity, and effects of fires prior to the advent of active suppression efforts in drder to determine the natural occurrence and influence of fire. No data was collected for the pinyon-juniper forest and inner canyon vegetation, but observations were made and used as a basis for discussing fire characteristics. A total of 227 fire scars were used to record 87 fire years. Twelve years were found common on both rims. A fire occurred somewhere in this forest on the average of once every 3 years. The best record was for the period 1900 - 1750, when suppression and grazing had the least effect. The average frequency then for fires reoccurring in a stand was 14 years with a range of 6 to 21 years. The incident of fire was very low since 1900, with 6 fires recorded in 82 years. This shows the effects of settlement, i.e., grazing and suppression. Most fires appeared to be small (less than 10 acres). However, evidence found throughout the forest showed fire was a widespread occurrence. In ponderosa, fires were low to moderate intensity burns that thinned and pruned stands and rejuvenated the plant. community. In pinyon-juniper fires were very small (a few trees) or large stand replacing burns. Inner canyon burns were small, rapid burns occurring in sparse vegetation. In these two areas they were much less frequent than in ponderosa pine.