Bark thickness across the angiosperms: more than just fire

Area of Science:

• Ecology
• Plant Biology
• Evolutionary Biology

Background:

• Total bark thickness (TBT) variation is often attributed solely to fire.
• Bark's multifunctionality, including inner living and outer dead regions, suggests other factors influence thickness.

Purpose of the Study:

• To investigate the contributions of fire, climate, and plant size to variations in TBT, inner bark thickness (IBT), and outer bark thickness (OBT).

Main Methods:

• Sampled 640 angiosperm species across 18 sites with diverse environmental conditions (precipitation, temperature, fire regime).
• Analyzed bark thickness in relation to stem size, climate variables, and fire frequency.

Main Results:

• Stem size was the primary driver of bark thickness variation.
• IBT correlated with stem diameter and was thicker in hotter, drier environments, suggesting a role in water/photosynthate storage.
• OBT showed less correlation with size and was thicker in drier, seasonal sites with frequent fires, indicating a protective function.

Conclusions:

• Bark thickness is influenced by multiple factors, including plant size and environmental conditions, beyond just fire.
• IBT and OBT have distinct drivers and contribute to TBT variation.
• Bark thickness is evolutionarily labile, with significant variation occurring within sites.