Costs and benefits of relative bark thickness in relation to fire damage: a savanna/forest contrast

Title
Costs and benefits of relative bark thickness in relation to fire damage: a savanna/forest contrast
Publication Date
2013
Author(s)
Lawes, Michael J
Midgley, Jeremy J
Clarke, Peter J
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
Wiley-Blackwell Publishing Ltd
Place of publication
United Kingdom
DOI
10.1111/1365-2745.12035
UNE publication id
une:13199
Abstract
1. In fire-prone ecosystems, bark protects the stem bud bank from fire. Absolute bark thickness is a good indicator of this protective function, but it depends on stem size as well as inherent differences between species. Relative bark thickness (i.e. relative to stem diameter) takes the latter into account. We argue that relative bark thickness is an important functional trait offering insights to the evolution of species persistence in fire-prone habitats. 2. During growth ontogeny different species can acquire absolutely thick bark through having: (i) relatively thick bark (i.e. an early commitment to thick bark) or (ii) relatively thin bark but fast stem diameter growth rates. We test the hypothesis that the most effective way of protecting tree stems from frequent fire is by having relatively thick-barked small stems. We predict that species with higher relative bark thickness are more common in fire-prone habitats. In habitats with long fire-free intervals such as rainforest, delayed investment in bark thickness results in thin bark. 3. We examined the relative bark thickness of woody congeners from Australian non-fire-prone forest and fire-prone savanna and in other tree-dominated systems world-wide. We determined the relative cost of acquiring absolute bark thickness of 0.5 cm for different rates of bark allocation. The insulating benefits of bark were considered a linear function of bark thickness. 4. Synthesis. We suggest that relatively thick bark minimizes the costs of acquiring absolutely thick bark, and it confers greater protection to smaller stems. The cost of acquiring thick bark prevents small trees from merely accumulating bark as a consequence of fast height or stem diameter growth. Accordingly, our field survey indicated that forest species had relatively thin bark and acquired thick bark only as a consequence of very large size, while fire-prone savanna species had relatively thick-barked small stems. Based on this, relative bark thickness appears to be a good predictor of local fire regimes and is a useful plant functional trait.
Link
Citation
Journal of Ecology, 101(2), p. 517-524
ISSN
1365-2745
0022-0477
Start page
517
End page
524

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