PARENT SESSION
Poster Session #18: Fire Ecology I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Fire tolerance of trees in tropical rainforest fragments.

BRADDEN, MAC¹, MIYANISHI, KIYOKO^*,1, ¹ University of Guelph, Guelph, ON, Canada

ABSTRACT- Long-term persistence of natural small species-rich rainforest fragments in a frequently-burned savanna in Belize is an interesting phenomenon with implications for maintenance of recent anthropogenic rainforest fragments. We hypothesize that their persistence is due to the presence of a suite of tree species at the savanna-forest boundary that are resistant to fire-kill, thus maintaining the integrity of the closed canopy environment and protecting the fire-sensitive core species. A field fire-heating experiment, comparing survival times (time for the cambium to reach 60°C) among 14 tree species with previously identified core or edge affinities based on spatial abundance patterns, showed that edge species were significantly more fire tolerant than core species. To understand the role of various bark properties in insulating the cambium, we used a heat transfer model where survival time is directly proportional to bark thickness squared and inversely proportional to bark thermal diffusivity (determined from conductivity, bulk density and specific heat). Since bark fiber, air, and water differ in these properties, bark moisture content influences diffusivity. The model provided a close fit to the data with thickness accounting for 76% of the variance in survival time, moisture content 13% and bulk density <1%. A survey of bark thickness of 500 trees (33 species), categorized by their spatial abundance patterns as core, generalist, edge and savanna species, showed that mean thickness of these groups was significantly different with groups ranked in the expected order from core to savanna.

KEY WORDS: rainforest, savanna, fragmentation, fire