COMPOSITION AND DISTRIBUTION OF EPIPHYTIC ORGANIC-MATTER IN A NEOTROPICAL CLOUD FOREST, COSTA-RICA

We describe the abundance (dry weight) of angiosperms and other organic matter suspended within the inner crowns of a dominant host tree species, Ocotea tonduzii (Lauraceae) in a Neotropical lower montane forest. Epiphytic organic matter (EOM), defined as vegetation and dead organic matter, was randomly sampled from inner canopy branches of ten trees in Monteverde, Costa Rica. Total EOM (grams per square decimeter of branch surface area) showed a strong positive correlation with branch circumference and a strong negative correlation with branch angle. Approximately three times more dry mass occurred on large (86-140 centimeters circumference) branches than on small (15-50 centimeters) branches, and four times more dry mass occurred on less inclined (less-than-or-equal-to 30-degrees) than on more inclined (>60-degrees) branches. The variation of EOM was much greater within trees (between branches) than among different trees. EOM was composed of approximately 60 percent dead organic matter, 20 percent live and dead roots, 10 percent angiosperms, 5 percent ferns, and 5 percent cryptogams. Sixty-five angiosperm species in 18 families, with no strongly dominant species, were found among the 75 percent of plots that supported angiosperms. Araceae, Bromeliaceae, Ericaceae, Melastomataceae, and Orchidaceae contributed about 70 percent of the angiosperm biomass. Orchidaceae and Piperaceae were the most frequently represented families and those with the most species in the study plots. The most species-rich plots (greater-than-or-equal-to 6 species) occurred on brandies >50 centimeters in circumference, but the highest density of epiphytic angiosperm seedlings occurred on smaller, presumably younger branches.