Seasonal Variation in Flammability Characteristics of Quercus marilandica and Quercus stellata Leaf Litter Burned in the Laboratory

John R Weir,Ryan F Limb

doi:10.4996/fireecology.0903080

Abstract

AbstractHistorically, the Cross Timbers forest of Oklahoma, Kansas, and Texas burned frequently. Fire managers in the region often have varied success when conducting prescribed fires, with one hypothesis being that fuel quality varies with litter age. This study was designed to determine the time-since-leaf-fall flammability characteristics of the two dominant tree species in the Cross Timbers, Quercus marilandica and Q. stellata. Principal components analysis indicated that the burn characteristics of both species are strongly influenced by time since the onset of leaf fall. The percent consumption of leaf litter and flame time of the two species began to diverge at 123 days after leaf fall and continued throughout the remainder of the study. There was no difference between the other flammability characteristics of ember time, total burn time, average temperature, and maximum temperature. Fuel consumption and fire behavior in hardwood leaf litter fuels can vary considerably, possibly as result of fuel mass loss from decomposition, which may due to a loss of flammable material. Our results show that the longer the time period from leaf fall to burn, the greater the change in burn characteristics of these two Quercus species. By identifying these similarities and differences between the leaf litter of dominant tree species, fire managers can adjust fire prescriptions to better meet burn objectives.

Highlights

Fire and human activity have affected the past and present ecology of oak forests (Abrams 1992)
But only with leaf litter collected right after leaf fall, consumption and flammability results for Q. stellata were comparable to our results right after leaf fall (Kane et al 2008), showing similar flammability characteristics for this species across regions
Quercus marilandica had greater consumption than Q. stellata, but consumption declined for both species over the year

Summary

Introduction

Fire and human activity have affected the past and present ecology of oak forests (Abrams 1992). The Cross Timbers, or post oak (Quercus stellata Wangenh.)-blackjack oak (Q. marilandica Muenchh.), forest contains about 19 million ha of upland hardwood forest-tallgrass prairie, ranging from southeastern Kansas, through Oklahoma, and into north Texas (Engle 1994). This region was prone to frequent fire (Stambaugh and Guyette 2006, Clark et al 2007, Stambaugh et al 2009), but due to settlement, landscape fragmentation, and fire suppression, the historic fire pattern has been interrupted. From other studies and personal experience of the senior author, the traditional late winter to early spring fires often fail to spread or consume little of the leaf litter fuels

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Conclusion