Cloud water interception of epiphytic bryophytes in a Peruvian upper montane cloud forest: an experimental approach

Epiphytic plants account for high proportion of biomass in tropical montane rain forests. In high-elevation cloud forests, where frequent fog passes through the canopy, the majority of this epiphytic biomass consists of bryophytes1. Together with physiological adaptations for water absorption and storage, bryophytes' abundance implies a regulatory role in the forest water cycle. Epiphytic bryophytes capture rain and fog droplets, potentially increasing water availability, and stabilize forest microclimate by slowly releasing the accumulated moisture. Their ecological impact on forest hydrology has been especially attributed to cloud water interception (CWI) during dry seasons2, but few studies have provided quantitative data to support this hypothesis3. We constructed an experimental design to measure the cloud water input into bryophyte assemblages on six artificial branches made out of plastic pipes. To contrast CWI efficiency to functional traits of bryophytes, we used four different dominant species (Plagiochila spp., Frullania sp, Herbertus sp. and Radula sp.) typical of different parts of the host tree. Our results show that bryophytes' water content changes following the daily fluctuations in temperature and humidity and that the magnitude of this variation is species-dependent. These findings highlight the importance of species composition as well as biomass on the ecohydrological functioning of bryophyte communities, both of which should be noted in conservation planning and management. References: 1Köhler L., Tobón C., Frumau K. A. & Bruijnzeel L. S. (2007). Biomass and water storage dynamics of epiphytes in old-growth and secondary montane cloud forest stands in Costa Rica. Plant Ecology, 193: 171-184. 2Hietz P. (2010). Ecology and ecophysiology of epiphytes in tropical montane cloud forests. In: Bruijnzeel, L.A., Scatena, F.N., Hamilton, L.S. (Eds.), Tropical Montane Cloud Forests: Science for Conservation and Management. Cambridge University Press, New York, pp. 67-76. 3Ah-Peng C., Cardoso A. W., Flores O., West A., Wilding N., Strasberg D. & Hedderson, T. A. (2017). The role of epiphytic bryophytes in interception, storage, and the regulated release of atmospheric moisture in a tropical montane cloud forest. Journal of Hydrology, 548: 665-673.