Biomass and mineral capital of epiphytes in an Acer macrophyllum community of a temperate moist coniferous forest, Olympic Peninsula, Washington State

Abstract

The epiphyte community of a Pacific northwest temperate rain forest makes up a conspicuous portion of the canopy, especially on the Acer macrophyllum trees that grow along river terraces of wet western slopes of the Olympic Mountains. Destructive sampling methods were used to assess the composition, biomass, and nutrient concentrations of live and dead epiphytes on representative host trees to determine the mineral capital contained in the epiphytic components of the standing vegetation. Average epiphyte standing crop on mature Acer macrophyllum trees is 35.5 kg. The nutrient capital (grams) is N, 370; P, 44; K, 145; Ca, 270; Mg, 50; and Na, 9. Although epiphyte biomass constitutes less than 2% of total aboveground ecosystem dry weight, it is equivalent to nearly four times the foliar biomass of host trees on a single-tree basis. Epiphytes are efficient at garnering nutrients from atmospheric sources and retaining them within the biotic portion of the ecosystem. They supplement the nutrient-gathering apparatus of host trees and buffer nutrient pulses on a short-term and on a seasonal basis.