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Tropical montane cloud forests (TMCFs) are ecosystems with high biodiversity that are threatened by deforestation, land use changes, and climate change. One of the unique aspects of TMCFs is the high biomass and diversity of epiphytes. Epiphytes are vascular and non-vascular plants that live in tree canopies, creating arboreal micro-ecosystems. They provide ecological services by capturing and retaining allochthonous nutrients from rain and fog, and by supporting the presence of canopy pollinators and other fauna. Predicted changes in cloudiness and land conversion threaten the abundance of epiphytes, and thus their capacity to contribute to ecosystem functions. However, how losses in epiphyte abundance will affect microclimate and host tree water status is still unclear and requires the ability to simulate the role of epiphytes in canopy water storage dynamics. We developed a water balance model for epiphytes in TMCFs. We consider epiphytes in the host tree as a water store inside the canopy that is filled via precipitation from both rain and fog, and depleted via evapotranspiration and host tree water uptake. The model was used to simulate water and energy fluxes between the epiphytes and their surroundings under idealized and real dry season conditions for TMCFs near Monteverde, Costa Rica. Results from the idealized and real simulations capture how epiphytes retain water under dry-down conditions, leading to small diurnal variability in temperature, low evapotranspiration rates, and enhanced dew deposition at night. We find that dew deposition recharges up to 34 % of epiphyte water storage lost due to evapotranspiration over a 3-day dry-down event. Our results provide the first quantitative demonstration of the importance of epiphyte water storage on temperature and dew formation in TMCFs. This work sets the foundation for developing a process-based understanding of the effects of epiphyte loss on TMCF ecohydrology. 

As watersheds are complex systems that are difficult to directly study, the streams that drain them are often sampled to search for watershed “signals.” These signals include the presence and/or abundance of isotopes, types of sediment, organisms (including pathogens), chemical compounds associated with ephemeral biogeochemical processes or anthropogenic impacts, and so on. Just like watersheds can send signals via the streams that drain from them, we present a conceptual analysis that suggests plant canopies (equally complex and hard-to-study systems) may send similar signals via the precipitation that drains down their stems (stemflow). For large, tall, hard-to-access tree canopies, this portion of precipitation may be modest, often <2%; however, stemflow waters, like stream waters, scour a large drainage network which may allow stemflow to pick up various signals from various processes within and surrounding canopies. This paper discusses some of the signals that the canopy environment may impart to stemflow and their relevance to our understanding of vegetated ecosystems. Being a conceptual analysis, some examples have been observed; most are hypothetical. These include signals from on-canopy biogeochemical processes, seasonal epi-faunal activities, pathogenic impacts, and the physiological activities of the canopy itself. Given stemflow's currently limited empirical hydrological, ecological and biogeochemical relevance to date (mostly due to its modest fraction in most forest water cycles), future work on the possible “signals in stemflow” may also motivate more natural scientists and, perhaps some applied researchers, to rigorously monitor this oft-ignored water flux. 

Abstract Stormwater is a vital resource and dynamic driver of terrestrial ecosystem processes. However, processes controlling interactions during and shortly after storms are often poorly seen and poorly sensed when direct observations are substituted with technological ones. We discuss how human observations complement technological ones and the benefits of scientists spending more time in the storm. Human observation can reveal ephemeral storm-related phenomena such as biogeochemical hot moments, organismal responses, and sedimentary processes that can then be explored in greater resolution using sensors and virtual experiments. Storm-related phenomena trigger lasting, oversized impacts on hydrologic and biogeochemical processes, organismal traits or functions, and ecosystem services at all scales. We provide examples of phenomena in forests, across disciplines and scales, that have been overlooked in past research to inspire mindful, holistic observation of ecosystems during storms. We conclude that technological observations alone are insufficient to trace the process complexity and unpredictability of fleeting biogeochemical or ecological events without the shower thoughts produced by scientists’ human sensory and cognitive systems during storms.