Buttress roots and prevailing winds| uprooting

Eric Frei

Buttress roots act as tension members to prevent Australian tropical rainforest trees (Argyrodendron spp) from uprooting in a cyclone

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Sean Freeman

Its an interesting topic for thought and discussion somewhat limited by the lack of the full paper/presentation....I also have strong reservations about the value of the simplified vector modelling.

My very limited interaction with the group from JCU who under took the analysis of post Larry building damage developed quite intricate and complex modelling of the wind vectors across the affected region, whilst their focus was on building impacts not trees the data reveals a pattern of complex vortices statistically influenced by indices of terrain roughness.

Combine this with what we have come to understand about the inherent dampening capacities of healthy tree canopies and the picture becomes far less clear and certain.

None of this is to say that their conclusions are without merit...just that it is hard to make definative calls based on what is available in the quoted text.

Eric Frei

From an engineering point of view it makes sense.

The resistance to a turning moment where there is a buttress is far greater than where there isn't a buttress .... if some-one were to push you in the chest to make you fall on your backside wouldn't it be easier if your feet were together rather than apart in a walking stance?

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Sean Freeman

Yes agreed Eric as a structure buttress roots even out the stresses that loading would otherwise concentrate at the union betwen root and root crown.

Well worth pointing out that the roots are as important in compression as tension...just not sure their data is really proving anything more than any of us could state as a general observation.

Eric Frei

Hey Sean,

A while back I did about a 6 hour off the beaten track walk through Lamington National Park from O'rielly's.

We saw some monster trees uprooted, saw some monster limbs also busted off and huge tops busted out. Anyway, you know with the large figs that have large butresses never saw one of them blown over but did see other figs without the buttresses blown over.

Anyway, another thing is when there's blow overs or blown downs, sometimes the force isn't a direct rotation or flipping of the tree (or hinging of the tree), it can also be a lifting force like holding an umbrella .... you ever feel that lifting force and the brella wanting to go up like Mary Poppins?

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