Species Richness and Cover of Orchids and Bromeliads on an Active Volcano

Abstract

Orchid and bromeliad species richness and cover were examined in 14 plots at 100-m intervals at 200-1500 m elevation along a 1957 flow of aa lava (blocky lava with a high silica content) on Concepción volcano in Nicaragua. Seventeen orchid species and four bromeliad species were recorded, using a point intercept method. Orchid and bromeliad species richness peaked between 600 and 1000 m and accounted for 50% or more of the species encountered. Orchid and bromeliad cover were greatest at 600-800 m and accounted for more than 50% of the vegetation cover. In particular, Sobralia spp. and Vriesea pedicellata accounted for the majority of vegetation cover at 700 and 800 m. Orchid and bromeliad species richness and cover were positively correlated with percent lichen cover and negatively correlated with herbaceous plant height. High temperature and low precipitation regimes apparently limit orchid and bromeliad distributions at low elevations, and competition with taller plants may limit their distribution at high elevations. Canopy orchids and bromeliads may play a key role in primary succession on active volcanoes in the tropics.