Height and stem diameter relationships for dicotyledonous trees and arborescent palms of Costa Rican tropical wet forest

RICH, P. M. (Harvard University, Harvard Forest, Petersham, MA 01366), K. HELENURM (Dept. Biology, Washington University, St. Louis, MO 63130), D. KEARNS (Institute of Ecology, University of Georgia, Athens, GA 30602), S. R. MORSE (Dept. Botany, University of California, Berkeley, CA 94708), M. W. PALMER (Dept. Botany, Duke University, Durham, NC 27706), L. SHORT (Dept. Botany, University of Wisconsin, Madison, WI 53704). Height and stem diameter relationships for dicotyledonous trees and arborescent palms of Costa Rican tropical wet forest. Bull. Torrey Bot. Club 113:241-246. 1986.-Allometric relationships between stem diameter and height were studied for dicotyledonous trees and arborescent palms in a tropical wet forest of Costa Rica. In a mixed population of dicotyledonous trees, stem diameter varies with the 3/2 power of height. The climax forest tree Pentaclethra macroloba (Willd.) Kuntze. appears to have a greater margin of safety against mechanical failure than the faster growing tree Pourouma aspera Trecul. This is consistent with Pourouma's shorter life span and narrower crown. As the arborescent palms Welfia georgii Wendl. ex Burret and Socratea durissima (Derst.) Wendl. grow in height, the margin of safety against mechanical failure decreases and/or the stem tissue stiffness and strength increases. Welfia shows little capacity to increase stem diameter during height growth. Socratea shows major stem diameter increase during height growth, but not enough to maintain elastic or geometric similarity. The tallest individuals of Socratea exceed McMahon's (1973) theoretical buckling limit for dicotyledonous trees. This is consistent with the observation that tall palms have stronger, stiffer stem tissue and narrower crowns than dicotyledonous trees. Differences in allometry of height and stem diameter indicate differences in stem tissue mechanical properties, the margin of safety against mechanical failure, and/or crown weight; however, we generally can not distinguish the relative importance of these three possibilities on the basis of studies of height and stem diameters alone.