Epiphyte biomass in Costa Rican old-growth and secondary montane rain forests and its hydrological significance

Epiphyte biomass and associated canopy water storage capacity may vary greatly in tropical montane forests depending on climate, forest structure, and stand age. This study compares old-growth and secondary forests in the upper montane belt of the Cordillera de Talamanca (Costa Rica) with respect to biomass of non-vascular and vascular epiphytes and their effect on water fluxes in the canopies of an old-growth forest, an early-successional stand (10–15 years of age), and a mid-successional stand (c. 40 years). Irrespective of stand age, epiphyte communities were strongly dominated by non-vascular plants (70–99% of total epiphytic biomass). Epiphyte biomass in the old-growth forest (3400 kg ha−1) was more than 20 times that of the youngest stand (160 kg ha−1) and more than six times that of the intermediate stand (520 kg ha−1). Consequently, the water storage capacity of non-vascular epiphytes and canopy humus increased from 0.06 mm in the early-successional, via 0.18 mm in the mid-successional, to 0.97 mm in the old-growth stand. Thus, the recolonization by epiphytes of tropical successional forests after clear-cutting, and the restoration of epiphytic water storage capacity will require many decades if not centuries.