Abstract
Fire management is increasingly used to manage forest stand structure and dynamics. Relatively intense fires can injure the tree stem and induce fire scar formation, affecting subsequent tree growth and wood quality. Here, we consider the physiological effects of fire scarring in white oak. Potential hydraulic conductivity, estimated from the mean vessel area and vessel number, was determined for growth rings formed before, during, and after the year of injury. We measured vessel anatomy using the ROXAS image analysis tool on the cross-sections of 14 white oaks of various ages with fire scars originating in different years through the late 19th and early 20th century. We found that the mean vessel area and potential hydraulic conductivity were significantly reduced for the year of and the year immediately following fire injury. After this two-year period, mean vessel area returned to levels present in wood formed prior to the injury. Age when scarred, radius from the pith when scarred, scar height above ground, and percentage of circumference scarred did not explain the degree to which potential hydraulic conductivity was lost in the fire scar year compared to the year prior. Overall, the magnitude of reduction in potential hydraulic conductivity was small but significant. An earlier study on the same cross-sections verified no reductions in radial growth after fire injury. Thus, it is likely that the conductance of older rings is adequate to sustain conductance. Nonetheless, we recommend further investigation, in particular, the ability to predict how tree size, age, position along a slope, and other variables may influence the degree of wounding and possible losses of potential hydraulic conductivity after the fire. Information like this for white oak and other common tree species may help elucidate the physiological impacts fire injuries have on trees existing in forest stands with periodic fire.
Highlights
One of the most well-known themes in forest ecology is the connection between fire and the global occurrence of oak-dominated forests
We considered how scar height, tree age when scarred, tree diameter when scarred, and percent of the circumference scarred affected the relationship between potential hydraulic conductivity and fire injury
For the final 14 cross-sections used in all subsequent analyses, Figure 3 shows the 95% confidence interval for for mean vessel number, mean vessel area (MVA),MVA, and Kr forKr raw, and ageandageclimate-detrended interval mean vessel number, and forage-detrended, raw, age-detrended, and and climatetime series over the
Summary
One of the most well-known themes in forest ecology is the connection between fire and the global occurrence of oak-dominated forests. From adaptations in mature trees related to minimizing injury and mortality [5,6], through the regeneration of new cohorts that persist through repeated fires by sprouting to gain a competitive advantage in post-disturbance environments [7,8,9], fire can play a central role in maintaining the structure and composition of oak-dominated forests [7,10,11]. Despite the evidence of enhanced oak regeneration and productivity after fire [18], the response of forestry professionals to prescribed burning is mixed, as fire can kill and damage individual trees and contribute to a considerable economic loss [19]. Important determinants of tree mortality and extent of economic value loss include the degree of fire injury as indicated by observations on fire scars and tree-related factors, including age and diameter when scarred [21,22,23]
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