Factors influencing plant species similarity between tropical forest fragments and coffee agroforests

Student First Name: 
Michelle
Student Last Name: 
Stuhlmacher
Student Picture: 
Michelle Stuhlmacher and team building transects in the Costa Rican rainforest
Project Picture: 
Road to forest fragment
Expected Year of Graduation: 
2015
Department/Major: 
Geography
Student Team Members: 
School for Field Studies, Center for Sustainable Development, Costa Rica
Mentor(s): 
Achim Haeger
Other Team Members: 
Rafael Acuña, Augustín Contreras, Rosy Cohane-Mann, Corie Gibson, Shannon Urato, April Martens, Matt Tsui, Justin Covino, Maura Welch, Erin Conway, Whitney Moore, Amanda Lam, Elise DiNuzzo, Paige Triola, Jim Casey, Cameron Wethern, Elie Mango & Claire Fox
Fun Fact About Yourself: 
Michelle spent a long time wandering the departments of Colombian College before declaring a major. All it took was one introductory course to Physical Geography and the rest is history.
Project Abstract: 

Agricultural deforestation results in a variety of environmental issues (i.e. greenhouse gas emissions, erosion, decreased diversity) but agroforestry or organic management reduces the impact of agriculture by continuing to provide some ecosystem services. This study examines the interaction of forests with agroforestry systems. It was expected that organic coffee farms would have a greater species similarity to surrounding forest fragments than conventional counterparts. Species similarity was also expected to increase as the amount of forest surrounding a coffee farm increased. Seven conventional and seven organic coffee farms as well as five forest fragments in the Central Valley of Costa Rica were studied. Woody stemmed plants (with a DBH of >5cm) in 1 ha plot were identified and species information was compared. Species similarity was calculated with the Sorensen similarity coefficient and an ANCOVA was used to analyze the effects of farm management and forest area on level of species similarity between farms and forests. The combined effects of forest area and farm type explained almost 40% of species similarity (R²Adj = 0.398, p = 0.024). Individually, the forest area had a significant effect (p = 0.0166) on species similarity but farm type's influence was not significant (p = 0.0934). Organic coffee farms had higher average species similarity (0.092 ± 0.032 vs. 0.071 ± 0.028) and biodiversity than conventional farms (24 ± 8.52 vs. 17.29 ± 6.18 species/ha). The positive species similarity relationship implies that forest fragments are the source of diversity for the farms and therefore important to maintaining tropical biodiversity.