Suites of Fire-Adapted traits of Oaks in the Southeastern USA: Multiple Strategies for Persistence

J Morgan Varner,Joseph W Veldman,J Kevin Hiers,Jesse K Kreye,Jeffrey M Kane

doi:10.4996/fireecology.1202048

Abstract

Fire is integral to the functioning of terrestrial ecosystems of the southeastern USA and is a strong selective force on plant species. Among woody plants, oak species (Quercus spp. L) have diverse life history traits that appear to reflect their evolution in this fire-prone region. Oaks also occur across wide gradients of fire frequency and intensity, from annually burned savannas to fire-protected forests. As such, oak functional traits are presumed to reflect adaptations to acquire limited resources (i.e., “physiological traits”) or survive environmental stress (i.e., “protective traits”). Oak functional traits may also influence fire regimes (i.e., via “flammability traits”) by altering fire behavior through effects on fuels and their combustion. We synthesized evidence from ecophysiological measurements, laboratory burning and drying experiments, and field experiments to determine the suites of functional traits that reflect fire adaptive strategies in eight Southeastern oaks for which abundant data were available. We found strong correlations among Principal Components Analysis axes for flammability (litter burning and drying), protective (bark and wound responses), and physiological (growth) traits. The eight oaks clustered into three strategies: 1) pyrophytic species that produce highly flammable leaf litter, accrue thick bark rapidly, close wounds rapidly, and grow slowly; 2) mesophytic species that produce low flammability litter, have thin bark, and are fast growing; and 3) fire-avoider species with a mixture of traits from the two extremes. This synthesis clarifies the relative pyrophily of Southeastern oaks and suggests how suites of fire-related traits influence fire regimes and species habitat preferences.

Highlights

Woody plants have developed a diversity of traits to decrease their susceptibility to fires, including investments in bark, responses to wounding, resprouting, storage or “banking” of seeds, and cued germination of seeds, among a host of other fire-adapted traits (Landers 1991, Bond and van Wilgen 1996, Keeley and Zedler 1998, Jackson et al 1999, Smith and Sutherland 1999)
The concept of “fire adapted strategies” has been covered in detail elsewhere, but in general, woody plant traits associated with fire can be categorized broadly into those that (1) enable survival of above-ground stems, (2) rely on resprouting of above-ground stems from bud banks, (3) rely on soil or crown seed banks, or (4) lack traits to survive fire (Agee 1993, Keeley and Zedler 1998; Figure 1)
We evaluated the relationships among functional traits in eight Southeastern oak species and identified potential multi-trait strategies

Summary

Introduction

Woody plants have developed a diversity of traits to decrease their susceptibility to fires, including investments in bark, responses to wounding, resprouting, storage or “banking” of seeds, and cued germination of seeds, among a host of other fire-adapted traits (Landers 1991, Bond and van Wilgen 1996, Keeley and Zedler 1998, Jackson et al 1999, Smith and Sutherland 1999). Flammability traits have been categorized (Fonda 2001), with species coarsely classified as those that promote or facilitate high intensity surface fires and those that dampen, diminish, or extinguish surface fires (Kane et al 2008, Kreye et al 2013, Mola et al 2014). The combination of these seemingly contradictory traits (self-protection and promotion of fire) has been evaluated in Pinus spp. Trait correlation in these cases suggests that species use multiple traits or “suites of adapted traits” to persist and increase in abundance in fire-prone landscapes

Methods

Results

Conclusion