While there are many ecosystems that are important to consider in the context of climate change, one of particular importance is the tropical montane cloud forest (TMCF). TMCFs comprise only 1.4% of all tropical forests but are important due to their high levels of biodiversity and endemism as well as their importance in local and regional surface hydrology. Unfortunately, these important and beautiful ecosystems are highly vulnerable both to changes in land use and climate. TMCFs are currently undergoing deforestation rates that exceed that of other tropical forests. In addition, increasing land and ocean surface temperatures even far away from these habitats may increase cloud base heights and alter the microclimate of the TMCF.

One of the unique features of the TMCF is the epiphyte community. Epiphytes are non-parasitic plants (such as orchids and ferns) that live on the trunks and branches of trees. In the TMCF, epiphytes form a dense mat of vegetation in the forest canopies which creates microhabitats for other organisms and stores water and nutrients that provide important inputs to the ecosystem. These epiphytes receive most, if not all, of their water from atmospheric inputs. Therefore, increases in cloud base heights and/or precipitation may be particularly detrimental to canopy communities. In the Gotsch lab, we are working to understand the vulnerability of this community and its importance to the ecosystem. Some of the questions that we are exploring are:

• How vulnerable are epiphytes in the TMCF to seasonal drought stress and changes in cloud cover or precipitation?
• What ecophysiological strategies do plants in the canopy community employ in different habitats that receive more or less precipitation and cloud immersion?
• How does water storage by epiphytes in the canopy affect the physiology of the host trees?
• What is the impact of these aerial gardens on the water cycling and water storage in the ecosystem?

In the Gotsch lab we determine ecophysiological strategies by measuring functional traits, leaf and stem anatomy, and we quantify physiological processes such as transpiration and photosynthesis and determine vulnerability of plants by measuring leaf water stress and stem hydraulic vulnerability.  To relate these physiological parameters to larger environmental issues, we conduct field and greenhouse experiments and collaborate with hydrologists, meteorologists and ecological modelers.