Environmental controls on dominance and diversity of woody plant species in a Madrean, Sky Island ecosystem, Arizona, USA

Abstract

The Sky Island archipelagos of the Sierra Madre Occidental contain diverse, highly endemic, and topographically complex ecosystems, yet the local and landscape-scale controls on woody plant dominance and diversity patterns are poorly understood. This study examines variation in woody plant species composition in relation to a suite of environmental variables (i.e., elevation, potential soil moisture, soil type, geologic substrate, and heat load) in the Chiricahua National Monument, Arizona (CHIR). Nine vegetation types were identified using cluster analysis that varied by species composition and plant life form. Non-metric multidimensional scaling and correlation analyses identified significant relationships between vegetation composition and elevation, potential soil moisture, and heat load. Rarefied species richness varied among vegetation types, and in relation to topography, with higher species richness occurring on more topographically complex sites. β (species turnover) and γ (landscape) diversity were also high in CHIR compared to other temperate forests. This study highlights the importance of local- and landscape-scale environmental controls on species diversity and vegetation patterns in Madrean evergreen woodlands.