Ecophysiology in Relation to Exposure of Pendant Epiphytic Bryophytes in the Canopy of a Tropical Montane Oak Forest1

Abstract

ABSTRACTWe investigated ecophysiological and morphological traits affecting light and water use of four commercially important pendant epiphytic bryophyte species in a montane oak‐bamboo forest in Costa Rica. Predictions based mostly on ecophysiological studies of temperate bryophytes and vascular plants were experimentally tested on tropical montane bryophyte species ranked on the basis of their distributions in the canopy from the most protected (1) to the most exposed sites (4): (1)Phyllogonium viscosum; (2)Pilotrichella flexilis; (3)Dendropogonella rufescens; and (4)Frullania convoluta. As predicted, highly exposed species tended to have higher light saturation and compensation points, higher dark respiration rates, more chlorophyll, higher chlorophylla:bratios, and higher nitrogen concentrations. Contrary to predicted trends, exposed‐site species had lower water contents at full saturation; there were no detectable differences among species in the rate of water loss. Rates of carbon gain in all species reached asymptotes with increasing water content, but the moisture compensation point for carbon uptake of the mossD. rufescenswas substantially higher than in the other species. Observed patterns result from interactions among processes related to water storage and transport operating at different scales and are determined by various morphological traits including the density, size, and disposition of phylloids, as well as by whole‐clump architecture.