Friday, August 7, 2009

PS 78-27: Epiphyte biodiversity and the coffee agricultural matrix: Canopy stratification and distance to forest fragments

Leigh C. Moorhead, Stacy M. Philpott, and Peter Bichier. University of Toledo


Agricultural matrix quality profoundly affects biodiversity and dispersal. Vegetatively complex coffee agroecosystems maintain species richness at larger distances from the forest. Yet few studies examine how coffee matrix quality affects diversity of epiphytic plants and none have examined vertical stratification and distribution of epiphytes in coffee agroecosystems with respect to nearby forests. Epiphytes colonize canopy trees and provide resources for birds and insects, thus any impact of agricultural production on epiphytes may affect other species.  We compared diversity, abundance, composition, and vertical stratification of epiphytes in a forest fragment and in two coffee farms differing in management intensity in southern Mexico. We additionally examined spatial distribution of epiphytes with respect to the forest to examine the quality of the two agricultural matrix types for epiphyte conservation. We sampled all vascular epiphytes in one forest fragment, a polyculture farm, and a shade monoculture farm at 100 m, 200 m, and 400 m from the forest. 

Epiphyte and orchid richness was greater in the forest than in the shade monoculture but not the polyculture farm. Epiphyte abundance and species composition differed with habitat type, but not with distance from the forest. In the forest, epiphytes were distributed throughout tree canopies, but in the farms, epiphytes were primarily found on trunks and larger branches. Epiphyte richness and species similarity to forests declined with distance to forest in the shade monoculture but not in the polyculture. Thus, polyculture coffee has greater conservation value. In contrast, shade monoculture coffee is likely a sink habitat for epiphytes dispersing from forests into the coffee.  Coffee farms differ from forests in terms of the habitat they provide thus protecting forest fragments is essential for epiphyte conservation. Nonetheless, in agricultural landscapes, vegetatively complex coffee farms may contribute to conservation of epiphytes more than other agricultural land uses.