Very interesting, Stumper. Our Cottonwoods here in upstate NY are almost all species Cottonwood, Populus Deltoides (of course with a few Lombardy Populars, but nothing like what Ontario, Canada, has). The branches mostly all are real thick off the trunk and will extend out quite a ways, but in comparison with most other trees, the ratio of the girth of the branch off the trunk, to the length of the limb, is relatively large. (The twigs, of course, are very brittle). I see this simply as a structural evolutionary compensation (since the chemical composition of the wood itself might not evolve as fast), due to thousands of generations of the species under selective pressure by gravity, winds, ice, etc.
That's why, as I see it, certain brittle-wooded trees don't fail nearly as often as we'd expect during storms. They've evolved structural compensations that perhaps we don't see so readily. Other trees that haven't failed nearly as much as I've expected during severe storms are Calery Pear, Zelcova, and Silver Maple. I have no explanation for these trees' relative resilience to storms, but I've seen them survive comparatively unscathed, while perfectly healthy Oaks, Hickories, and Sugar Maples have failed. Of course, my observations are not scientific, just anecdotal. I'll admit there's a lot of bias in personal observation, so maybe some feeback can prove me wrong.
Chucky
