Measuring stability of baldcypress and laurel oak with static winching

We evaluated the structural response to simulated wind stress applied to
two coastal tree species native to the southeastern USA that have
contrasting rates of windthrow during hurricanes: Baldcypress (Taxodium
distichum) and laurel oak (Quercus laurifolia). In a static winching
study, we evaluated the stability of 30 individuals each of laurel oak and
baldcypress by quantifying the critical turning moment required to cause
structural failure. Biomass of trunk segments and branches was measured
directly in the field for a subset of trees pulled and used to develop
regressions to determine biomass of other trees. Baldcypress were more
likely to snap than uproot, while the opposite was true for laurel oak.
Baldcypress critical turning moments were higher than laurel oak based on
biomass, but were similar when compared by diameter and other size
proxies, and ranged from 10.9–43.9 kN m. Models that incorporated crown
size and shape indicated smaller baldcypress could withstand higher wind
speeds than laurel oak before failing. Unlike laurel oak, many smaller
baldcypress were so flexible that they bent to the ground instead of
failing. We conclude that baldcypress will remain wind resistant and thus
ecosystem services and functions provided by this species should be
maintained. Conversely, laurel oak, while stable at large diameters, is
more likely to experience catastrophic failure and be less stable at
smaller diameters than baldcypress, which suggests that their presence in
built environments should be carefully evaluated.