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Trunk bending at 120mph

split barkCloseup of the lower portion of trunks bending in 120mph wind showed that the three pruning treatments resulted in the same lower trunk bending, and all three bent less than non-pruned trees. The inclinometer that measured lower trunk angle is visible in each closeup photograph. However bending on the upper portion of the tree was least for thinned and reduced trees; raised trees faired no better than trees that were not pruned. Raised trees in this study could be expected to act like lions-tailed trees in the landscape. Reduced trees might act like trees that received structural pruning.

Average angle of trunk from the vertical on 5 trees in 120mph wind is listed under each photograph.
Pruning treatment Before testing During testing
No pruning unpruned tree

trunk angle

Lower trunk angle = 27
Upper trunk angle = 46

Reducing

crown reduced in height

Crown was reduced in height using a reduction cut.

trunk angle

Lower trunk angle = 10
Upper trunk angle = 17

Thinning

thinned tree crown

Crown was thinned by removing primary branches back to trunk.

trunk angle

Lower trunk angle = 12
Upper trunk angle = 23

Raising

raised crown on tree

Crown was raised be removing lowest branches.

tree trunk angle

Lower trunk angle = 10
Upper trunk angle = 31