Biomass and nutrient pools of canopy and terrestrial components in a primary and a secondary montane cloud forest, Costa Rica

Abstract

Canopy-dwelling epiphytes and their associated dead organic matter exist as complex subsystems of many forests, but they have only rarely been quantified in the context of the whole ecosystem. We assessed the biomass and nutrient capital of canopy-dwelling and terrestrially rooted components of a primary and an adjacent secondary montane forest in Monteverde, Costa Rica. Total aboveground terrestrially rooted biomass (dry weight) was 490.1 and 151 t ha −1 in the primary and secondary forest, respectively. The primary forest supported a total canopy biomass of 33.1 t ha −1; the secondary forest supported only 0.5% of that, 0.2 t ha −1. Trunk and branch epiphyte biomass in the primary forest was over 40 times and 100 times greater than trunk and branch epiphyte biomass in the secondary forest. The bulk (ca. 95%) of the ecosystem biomass is trunk and branch wood, which is slower to decompose than the non-woody, labile components of foliage and non-woody epiphytes. In contrast to the primary forest, where dead organic matter (crown humus, intercepted litterfall) comprised over 60% of the total epiphytic material, there were only trace amounts in the secondary forest. The important ecosystem roles performed by this material in the primary forest (e.g., retention of atmospheric nutrients, habitat for canopy invertebrates, and substrate for wildlife and bird foraging) are virtually absent in the secondary forest canopy.