Treefalls, Crown Asymmetry, and Buttresses

Crown asymmetry may have important consequences for forest dynamics. Previous research has shown that the tendency for tree crowns to grow laterally away from neighbours was associated with increased tendency for gap-edge trees to fall into preexisting gaps. We report the fates over a 6.7-year period of 127 trees whose crown shapes had been mapped previously in a tropical broad-leaved forest in Panama. We demonstrate directly that trees tended to fall on their heavy sides, and that more asymmetrical trees were more likely to fall than less asymmetrical trees. Using data from two different forests (in Panama and Costa Rica) we also show that buttress formation is greatest on the sides of trees away from the direction of crown asymmetry, supporting the hypothesis that buttressesin tropical trees serve at least partly as tension elements (...)