2025 CSDMS meeting-059
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A novel model uncovers the importance of dew deposition for canopy epiphytes in a tropical montane cloud forest
David Carchipulla-Morales,
(he/him/his),Wake Forest University Winston-Salem North Carolina, United States. carcpd21@wfu.edu
Tropical montane cloud forests (TMCFs) are ecosystems at high elevation where fog and low clouds regularly occur. These forests are routinely wet, which promotes biodiversity and plant richness not seen in other parts of the world. A key feature of TMCFs is the abundance of epiphytes, plants that live along the branches and trunks of trees and collect their water and nutrients from the atmosphere. Epiphytes can be vascular and non-vascular plants and usually store water about 4 times their dry weight in water. A critical gap in our understanding of hydrologic processes in TMCFs is the role that epiphytes play as water stores in the canopy. Deforestation and land use changes threaten the boundaries of TMCFs, frequency and amount of fog and low cloud immersion, and the abundance of epiphytes. In order to investigate how the loss of epiphytes or changes in patterns of fog and low clouds will affect TMCFs, we developed an epiphytes water balance model (EWB). The EWB model conceptualizes epiphytes in the host tree as a water store inside the canopy that is filled via vertical and horizontal precipitation, and depleted via evapotranspiration and host tree water uptake. We tested the model using idealized and observed dry season conditions for TMCFs in Monteverde, Costa Rica. Results from the idealized and real model simulations capture how epiphytes regulate water and energy fluxes in the canopy at diurnal scales, and are consistent with field observations. A key result is that dew deposition may recharge up to 34% of epiphyte water storage lost due to evapotranspiration over a 3-day dry-down event. We also found that energy and water mass balances are sensitive to the water storage size, i.e. the maximum water content and the abundance of epiphytes in the canopy. Our results provide the first quantitative demonstration of how epiphytes regulate temperature in TMCFs. This work sets the foundation for developing a process-based understanding of the effects of climate change on TMCF eco-hydrology.
