Abstract
Bark thickness is a key structural feature in woody plants in the protection against fire. We used 19 provenances of Pinus halepensis, an obligate-seeder species, in a replicated common garden at two environments contrasting in water availability to assess the interacting effects of site environment and population in the relative allocation to bark, expecting lower allocation at the drier site. Secondly, given the average fire frequency, we analyzed whether trees reached the critical absolute thickness soon enough for population persistence via aerial seed bank. Our analyses indicated that trees at the moister site allocated a rather fixed quantity of resources independent of tree size, and almost all populations reached critical absolute bark thickness to eventually survive fire. In contrast, at the drier site allocation to bark reduced with tree size, and most populations did not reach the critical bark thickness. Populations from areas with higher fire frequency had thicker basal bark, while those from areas with severe droughts and short vegetative periods, had thinner bark. In conclusion, drought-stressed trees have a higher risk to die from fires before achieving reproduction and building a sufficient aerial seed bank.
Highlights
Bark is a key structural feature in woody plants, and the correlation between bark thickness and fire regime has recently attracted increasing interest by plant scientists (Pausas, 2015, 2017; Rosell, 2016)
We focused our research on Pinus halepensis Mill., a wellstudied model species in Mediterranean fire-prone ecosystems (Ne’eman et al, 2004)
We found that measuring bark thickness at a single point was accurate enough given the uniformity of P. halepensis bark at this age
Summary
Bark is a key structural feature in woody plants, and the correlation between bark thickness and fire regime has recently attracted increasing interest by plant scientists (Pausas, 2015, 2017; Rosell, 2016). Bark thickness is the most studied bark property so far, due to its correlation with cambial insulation and protection, especially against fires The degree of heat insulation by bark increases with the square of its thickness (Hare, 1965; Vines, 1968; Peterson and Ryan, 1986). Bark thickness strongly decreases the thermal diffusivity –the most important bark protective property (Vines, 1968)
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