Effectiveness Of Litter Removal To Prevent Cambial Kill-Caused Mortality In Northern Arizona Ponderosa Pine

Removal of deep litter and duff from the base of mature southwestern ponderosa pine (Pinus ponderosa Laws.) is commonly recommended to reduce mortality after prescribed burns, but experimental studies that quantify the effectiveness of such practices in reducing mortality are lacking. After a pilot study on each of four sites in northern Arizona, we monitored 15-16 sets of 8 matched trees on areas designated to be burned and adjacent not-burned sites and randomly assigned one of four litter and duff removal (to mineral soil) treatments: (1) rake to a distance of 23 cm from the bole, (2) leaf blow to a distance of 23 cm, (3) rake to a distance of 1 m, and (4) no litter or duff disturbance or removal. By 3 years postburn, no trees had died because of any of the treatments, but litter and duff removal prevented most cambial kill. However, 17% of the burned, no removal trees had some cambial kill. Litter and duff removal to 23 cm was as effective in preventing cambial kill and bole char as removal to 1 m, and there was no difference between removal by raking versus leaf blower removal. These results suggest that litter and duff removal is not needed to prevent ponderosa pine mortality after fall prescribed burns, but removal to 23 cm is adequate to prevent spots of cambial kill or moderate bark char. FOR. SCI. 56(2):166-171.