How fire scars are formed: coupling a disturbance process to its ecological effect

Abstract

Using results from the field and laboratory, we give a detailed explanation of an important and commonly observed ecological phenomenon, fire scarring of trees. Four key observations associated with the formation of fires scars are explained using fluid dynamics and heat transfer processes. When a fire passes by a tree, its height increases on the tree's leeward side because of the occurrence of two leeward vortices. The flame height increases in the vortices because the turbulent mixing of fuel and air is suppressed. The flow of gaseous fuel in the vortices becomes greater than the rate of mixing with the air, and hence there is an increased height along which combustion can occur. Fire scars are found only on the leeward side of trees because the vortices increase the residence time of the flame on the leeward side of the tree compared with the residence time of the flame on the tree's windward side. This leads to differential heating around the tree bole. Small trees rarely have fire scars because their cambium is usually completely killed by a passing fire and (or) their foliage is killed by crown scorch. Fire scars are usually triangular in shape; wider at the base and decreasing in width with height. The triangular shape is a result of the temperature isotherms within the standing leeward flame, which are triangular in shape.

Establishing Local Master Ring-Width Chronologies and Their Utilization for Estimating The Age of Big Old Trees

“…For such cross-dating therefore more local master tree-ring chronologies have to be established at the least based on the distribution map for precipitation. (Gutsell and Johnson, 1996;James, 2010). 갑 작스런 생육 변화(기상변화, 경쟁)로 수목생장이 불 량하게 될 경우 발생되는 미세연륜(narrow ring), 위 연륜(false ring), 실연륜(missing ring), 불연속륜 (discontinues ring) 등을 찾아내야 하는 어려움이 존 재한다 (Schweingruber, 1988).…”

Mitigating old tree mortality in long-unburned, fire-dependent forests: a synthesis

“…Although trees can be scarred numerous times from reoccurring fires and survive, exposed fire scars are particularly susceptible to further injury in subsequent fires, especially if decayed wood is present. The leeward side of the tree, usually the uphill side in sloped areas, is most susceptible to cambium injury because of increased residence times, flame lengths, and temperatures as flames wrap around the backside of the tree and create vortices (Gill 1974;Gutsell and Johnson 1996). Guyette and Stambaugh (2004) found 90 percent of fire scars were located on the uphill side of the tree in mixed oak-shortleaf pine (Quercus spp.…”

Fire Regime in Marginal Jack Pine Populations at Their Southern Limit of Distribution, Riding Mountain National Park, Central Canada

“…Direction of fire spread was estimated by converting the compass bearing for the fire scar orientation to a cardinal direction. The scars were assumed to have formed on the leeward side of the tree during a fire event [23,51]. Only the first scar was used for the direction analysis because subsequent scarring is often more likely to occur after the first burn due to exposed cambium and thinner bark in the region of the first scar [23].…”