Nutrient release from epiphytic bryophytes in tropical montane rain forest (Guadeloupe)

Abstract

Drought exposure in the upper canopy of tropical montane rain forest (Guadeloupe) leads to the pulsed release of solutes from epiphytic bryophytes within the cloud forest canopy. This efflux, leached from newly rewetted mosses and hepatics, was greatest for ions normally held within intracellular pools. Estimates of solute efflux from stem segments of canopy bryophytes reached 80.1 kg ha−1 year−1 for K, 1.4 kg ha−1 year−1 for P, and 11.8 kg hal−1 year−1 for N during experimental rewetting episodes. Estimates of solute efflux from intact bryophyte mats during field rewetting episodes were smaller, only 28.7 kg ha−1 year−1 for K and 0.2 kg ha−1 year−1 for P. The difference between these measurements is thought to reflect internal recycling of released ions within the canopy bryophyte mats during rewetting episodes. Nonetheless, nutrient loss to throughflow solution represents a significant portion of the standing nutrient capital held within canopy bryophyte mats. By releasing previously sequestered nutrients, bryophyte communities not only provide access to resource pools that would otherwise be inaccessible, but may stimulate the further transformation of nutrients as leaf epiphyll and decomposer communities respond to enriched throughflow solution pulses. These data suggest that recycling of nutrients between members of the standing biomass in tropical montane rain forest is not a steady state process, as often envisaged, but rather may be highly episodic in nature. Key words: tropical montane rain forest, bryophytes, epiphytes, nutrient cycling, throughflow.