Abstract
As forests become increasingly fragmented and degraded, land-sharing practices that allow human uses and biodiversity to coexist become even more important. In this dissertation, I evaluate the potential for shade-grown coffee farms to offer habitat for epiphytes-plants that grow in trees without connection to the ground-while simultaneously benefitting farmers. My work combines methods from community and functional ecology with those from people-environment geography. I integrate these data to paint a comprehensive picture of the potential for shade coffee farms to fulfill the needs of both plants and people. In the chapters that follow, I use data from 31 shade coffee farms and 2 protected forests to consider the ecology of epiphytes in shade coffee, including community assembly and environmental filtering, and the interests of farmers in managing trees within their farms. I first investigate how epiphytes initially colonize shade trees, looking at a chronosequence of tree age across 87 plots to follow epiphyte accumulation over time. Epiphytes take several years to initially colonize trees, but colonization accelerates over time. Key taxonomic groups accumulate in shade trees at different rates and environmental filtering and dispersal limitation appear to drive community assembly. Because epiphyte communities take considerable time to establish, newly planted trees in coffee farms require consistent land tenure and long-term management to become valuable habitat for diverse epiphyte communities. Stand age and complexity interact with farm macroclimate to determine epiphyte species composition in shade coffee farms. I use structural equation modelling to assess the relative strength of these factors in structuring epiphyte communities. While stand structure and climate both have strong effects on epiphyte richness, the effect of climate is mostly mediated through bryophyte cover. Since bryophytes are highly susceptible to desiccation and vulnerable to climate change, vascular epiphyte species that strongly associate with them may also be at risk. Abiotic conditions in shade coffee farms are warmer and drier than in forests, so differences in functional traits between epiphytes in the two habitat types may foreshadow functional shifts under climate change scenarios. Distributional data from two coffee farms and adjacent protected forest and functional trait data for 37 common species suggest that epiphytes in coffee farms may be responding to multiple layers of abiotic factors including microclimate within the tree, microclimate within the farm, and macroclimate across the landscape. Moreover, while some epiphyte groups seem to follow similar trait spectra as ground-rooted taxa, those rules may not hold true for all epiphytes. To put these ecological findings into context, I conducted 33 semi-structured interviews with owners and managers of shade coffee farms. While coffee producers value trees for the many ecosystem services they provide, they know very little about epiphytes. Economic situation, access to technical knowledge, and producers' personal values all influence tree management, and thus epiphyte habitat, on farms. Because farmers saw many benefits from trees and few detrimental effects of epiphytes, there is great potential for conservation interventions to add and maintain trees in coffee farms, providing suitable substitute habitat for many epiphyte species.