Background/Question/Methods In the tropics, the canopy habitat is a critical interface between the atmosphere and the rest of the forest. Rainforest canopies, in particular, contain resident epiphytes that represent up to 33% of the species in vascular flora. Epiphytes also play a large role in buffering evapotranspiration rates from their host trees and nutrient deposition reaching the forest floor. Therefore, how epiphytes will respond to global warming and nutrient addition is a crucial question to ask when building predictive models of whole ecosystem response. This study investigated the effects that temperature stress (3°C increase) combined with varying nutrient addition has on Vriesea cathyi (a tank epiphyte). We monitored relative growth rates for a 14 month period, conducted trichome and stomata density assays, analyzed specific leaf area, and conducted a nitrogen isotope uptake analysis along with an elemental analysis. This provided us with life history data from over 80 individuals across two temperatures and four nutrient addition levels.

Results/Conclusions We found that temperature significantly affected biomass production, relative growth rates, leaf physiology, and nutrient uptake. There were significant effects of temperature regime on trichome and stomata density as well as on specific leaf area. C:N content and ratios were significantly affected by nutrient addition level but not by temperature. Uptake rate of nitrogen was significantly greater in the warmer temperature and shown to be significantly affected by nutrient addition level. These results indicate that tank epiphytes will potentially be affected by increases in global temperature as well as changes in nutrient availability.