ECOLOGICAL CONSEQUENCES OF ROOT GRAFTING IN TABONUCO (DACRYODES-EXCELSA) TREES IN THE LUQUILLO-EXPERIMENTAL-FOREST, PUERTO-RICO

Root grafting was commonly found in cabonuco (Dacryodes excelsa Vahl), a dominant tree species of tabonuco forest in the subtropical wet for est of Puerto Rico. Over 60 percent of all stems and basal area of tab onuco occurred in unions, dumps of trees interconnected by root grafts . Self and intraspecific grafting were extensive, while interspecific grafting was not common in tabonuco trees. Seedlings and saplings did not show any grafting, probably because of their size or age. Grafted trees were taller and had a smaller crown/DBH ratio. Hurricane damage was significantly higher in isolated individual tabonuco trees than th ose in unions. Weak relationships between diameter class, area, and si ze of union, and inter-tree distances and the sum of the trunk circumf erences of the two nearest neighbors suggested that a noncompetitive f orce such as root grafting was more important than competitive forces in maintaining the unions of tabonuco, and thus the forest community. A conceptual model of the costs and gains of tabonuco in unions is pre sented.