Evolutionary trends in safety factors against wind-induced stem failure

Area of Science:

• Paleobotany
• Evolutionary Biology
• Biomechanics

Background:

• Early land plants evolved in terrestrial environments subject to wind forces.
• Increasing plant height during evolution may have increased susceptibility to wind-induced failure.
• Understanding the biomechanical safety factors of early plants is crucial for reconstructing their ecological roles.

Purpose of the Study:

• To test the hypothesis that safety factors against wind-induced stem failure remained high during early land plant evolution.
• To investigate the relationship between plant height, wind forces, and stem integrity in Paleozoic flora.
• To develop a protocol for assessing wind effects on early plant evolution.

Main Methods:

• Computed drag forces, stresses, and moments for 17 Paleozoic plant species.
• Calculated safety factors using the ratio of stem-tissue breaking stress to maximum wind-induced bending stress.
• Modeled plants within densely packed communities with equivalent heights and a consistent wind profile.

Main Results:

• Highest safety factors were found in ancient rhyniophyte and zosterophyllophyte species.
• On average, safety factors decreased in taller, geologically younger species.
• Tallest species (e.g., Archaeopteris) exhibited safety factors comparable to or higher than some presumed ancestors.

Conclusions:

• Results support the hypothesis of high safety factors against wind-induced failure in early land plants.
• Trends in safety factors were statistically robust among rhyniophytes and their descendants.
• The developed protocol offers a reasonable approach to explore wind's effects on early plant evolution, despite limitations.