Structural Function of Buttresses of Tachigalia Versicolor

To the test the hypothesis that buttresses serve as tension members for structural support of lowland tropical trees, measurements were made of 518 buttresses from 100 Tachigalia versicolor trees. Buttress size, particularly buttress height, increased at a more rapid rate than tree size or number of buttresses. No significant polar orientation was found in the distribution of individual buttresses relative to prevailing wind direction or to the direction of tree lean. However, buttresses that were, by chance, oriented into the prevailing wind, or located on the side of a tree opposite the direction of a visually perceptible lean, tended to be longer, taller, and more voluminous. The concentration of buttress tissue on the windward side of trees and on the side opposite the direction of declination suggests that proliferation of buttresses is a response to wind—induced and lean—induced stresses and that buttresses serve a function as tension members providing structural support to this species. While direction of lean was somewhat dependent upon wind direction, the constant unidirectional stress exerted by a leaning bole was more significantly related to buttress size proliferation than was the stress exerted by wind alone.