Spatial patterns and habitat associations of Fagaceae in a hill dipterocarp forest in Ulu Gadut, West Sumatra

Abstract

Abstract:Spatial distribution patterns and habitat associations of Fagaceae species in a Fagaceae-codominated hill forest in Sumatra were investigated. Ten Fagaceae species believed to be zoochorous (animal-dispersed seed) and five codominant canopy and emergent anemochorous (wind-dispersed seed) species from Anacardiaceae and Dipterocarpaceae were studied. Five Fagaceae species and all codominant anemochorous species were significantly aggregated while the other five Fagaceae species showed a random distribution pattern. The median distance of small saplings from the nearest reproductively mature tree tended to be shorter for aggregated species than spatially random species. This implied that some Fagaceae species dispersed over longer distances than anemochorous species. Relationships between four habitat variables and distribution of the target species were examined with torus-translation tests. ThreeQuercusand oneLithocarpusspecies showed positive habitat associations. TwoQuercusspecies aggregated at the preferred habitat, but the others were randomly distributed. Thus tree species with specific habitat preference do not only aggregate at the preferred habitat. The three ridge-specialistQuercusspecies showed gradual changes in habitat association, which could reflect avoidance of competition among the species. Most of theLithocarpusspecies showed little correlation with habitat variables. Coexistence of the threeQuercusspecies partly reflected subtle differences in topographical preferences. Distribution of five of the sixLithocarpusspecies was unrelated to topography, so other mechanisms must be sought to account for the maintenance of coexistence in this species-rich genus.