title: Distribution of vascular epiphytes along a tropical elevational gradient: disentangling abiotic and biotic determinants.
abstract: Epiphytic vascular plants are common species in humid tropical forests. Epiphytes are influenced by abiotic and biotic variables, but little is known about the relative importance of direct and indirect effects on epiphyte distribution. We surveyed 70 transects (10 m × 50 m) along an elevation gradient (180 m-1521 m) and sampled all vascular epiphytes and trees in a typical tropical forest on Hainan Island, south China. The direct and indirect effects of abiotic factors (climatic and edaphic) and tree community characteristics on epiphytes species diversity were examined. The abundance and richness of vascular epiphytes generally showed a unimodal curve with elevation and reached maximum value at ca. 1300 m. The species composition in transects from high elevation (above 1200 m) showed a more similar assemblage. Climate explained the most variation in epiphytes species diversity followed by tree community characteristics and soil features. Overall, climate (relative humidity) and tree community characteristics (tree size represented by basal area) had the strongest direct effects on epiphyte diversity while soil variables (soil water content and available phosphorus) mainly had indirect effects. Our study suggests that air humidity is the most important abiotic while stand basal area is the most important biotic determinants of epiphyte diversity along the tropical elevational gradient.
authors.affiliation: Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, 100091 China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Institute of Resource Insects, Chinese Academy of Forestry, Kunming, 650224, China.
authors.forename: Guangfu
authors.initials: G
authors.lastname: Liu
authors.affiliation: Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, 100091 China.
authors.forename: Runguo
authors.initials: R
authors.lastname: Zang
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China.|Section for Ecoinformatics and Biodiversity, Department of Bioscience, Aarhus University, Aarhus C, DK-8000, Denmark.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, 100091 China.
authors.forename: Xinghui
authors.initials: X
authors.lastname: Lu
authors.affiliation: Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, 100091 China.
authors.forename: Jihong
authors.initials: J
authors.lastname: Huang
mesh_terms: D000531:Altitude; D044822:Biodiversity; D002681:China; D017753:Ecosystem; D005163:Factor Analysis, Statistical; D008962:Models, Theoretical; D058526:Plant Vascular Bundle / Q000502:physiology*; D013045:Species Specificity; D014329:Tropical Climate