These traits allow species to endure heating (via thick bark) or to “resprout” quickly capturing growing space and available water, nutrients, and light ( Agee 1993).
Fire-adapted traits are numerous and have been classified in various ways ( Keeley and Zedler 1998), with two of the most important for persistence in fire-prone environments being rapid bark accumulation and vegetative regeneration ( Bond and Van Wilgen 1996). Fire-prone ecosystems are therefore dominated by pyrophytes with traits that enable persistence in response to fire frequency, intensity, and severity ( Bond and Van Wilgen 1996, Bond and Keeley 2005, Simon et al. Fire plays an important role in the evolutionary environment of fire-adapted ecosystems through dynamic interactions in which fire both affects and is affected by the species and environment ( Pausas and Keeley 2009, Bond and Scott 2010). The dynamics, composition, and spatial structure of species are intertwined with the climate, soils, and disturbance regimes of their ecosystem. These results confirm the adaptive importance of bark thickness to enhancing species survival in frequent fire regimes. Red maple, a commonly cited invader during fire-free intervals, invested the least in bark thickness and, with rock chestnut oak, had an average height and height:diameter ratio significantly greater than blackjack oak and all other species, respectively. Bark taper revealed that while other species allocated similarly to bark along the length of their stem, blackjack oak allocated much more at its base (in the flaming zone) and relatively less as height increased. Bark comprised over half (bark:wood = 0.55) of the basal diameter of blackjack oak, which was 3×, 4×, and 6× greater than the bark:wood ratio of sand hickory and rock chestnut oak, common persimmon, and red maple, respectively. Using bark thickness and inside bark diameter measurements taken at 20-cm intervals along the main stem of saplings (average age 4–5 years) we found that, while average wood diameter did not differ across species, significant differences occurred in the ratio of bark to wood. Sampled species included blackjack oak ( Quercus marilandica), sand hickory ( Carya pallida), common persimmon ( Diospyros virginiana), rock chestnut oak ( Quercus montana), and red maple ( Acer rubrum).
We compared bark accumulation in five co-occurring hardwood species within a longleaf pine ( Pinus palustris) ecosystem in the mountains of northeastern Alabama, USA. A key aspect of tree survival is rapid accumulation of protective bark within fire return intervals. Fire affects numerous aspects of plant growth and anatomy, particularly in those species adapted to persist in fire-prone environments.
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