Influences of edaphic factors on the distribution and abundance of a rare palm (Cyrtostachys renda) in a peat swamp forest in eastern Sumatra, Indonesia

Tropical plant community ecology is often assumed to be driven largely by stochastic disturbance, replacement and demographic processes despite a general lack of information about the physical environment. Tropical soils are more diverse, at regional, intermediate and local scales than usually is recognized. This study was conducted to test hypotheses about the importance of edaphic parameters in determining the abundance and distribution of the rare lipstick palm Cyrtostachys renda Blume and its co-occurrence with other plants. Eight of 11 tropical tree species were positively associated with C. renda. For Gluta renghas, Shorea parvifolia, Eleiodoxa conferta, Pandanus terrestris and Korthalsia flagellaris, the association with the palm was strong. The palms E. conferta and K. flagellaris appeared to have similar ecological and habitat requirements. The lipstick palm is adapted to specific edaphic conditions related to soil quality and drainage. It prefers fine sand, well-drained soil and low mineral content, reflected in associations between these variables and stem density, clump density, clump size, frequency, basal area and canopy circle area. High levels of soil Ca++, Mg++ and K+ are associated with sites where the palm is absent. The C/N ratio of soils appears to influence palm densities and sizes. All known populations occur in habitats with C/N-values less than 19, with the largest populations in areas with C/N-values of 13. Our findings suggest that edaphic variables are important determinants of the abundance and distribution of this tropical peat swamp forest species. © 2006 Ecological Society of Australia.