Burning characteristics of needles from eight pine species

Abstract

Ponderosa pine (Pinus ponderosa), Jeffrey pine (P. jeffreyi), longleaf pine (P. palustris), and south Florida slash pine (P. elliottii var. densa) are fire resisters. Trees of these species are able to survive the direct effects of wildfires. Monterey pine (P. radiata), knobcone pine (P. attenuata), sand pine (P. clausa), and jack pine (P. banksiana) are fire evaders. Trees of these species are killed by wildfire, but species survive on the postfire site via seed germination. Needles were burned in a 2×2 factorial experiment to compare these eight species, all of which are prominent in fire-related communities. The experiment tested two factors - fire adaptive strategy (resisters vs. evaders), geographic region (western vs. eastern United States) - and interactions between those two factors. Flame height, flame time, ember time, burn time, percent fuel combusted, and mean rate of weight loss were measured. Longleaf pine, ponderosa pine, and south Florida slash pine had the highest values for flame height, percent fuel combusted, and mean rate of weight loss. Knobcone pine and Monterey pine had the longest ember time and burn time. Sand pine and jack pine had the longest flame time. Resisters tested highest in flame height, percent fuel combusted, and mean rate of weight loss. Evaders had greater flame and burn times. Western pines were significantly greater than eastern pines in all burning characteristics except flame time and mean rate of weight loss. Significant interactions between fire adaptive strategy and geographic region existed for all burning characteristics except mean rate of weight loss. The interaction was accounted for primarily by differences between western evaders, which had some of the highest values for each characteristic, and eastern evaders, which had some of the lowest values.