Differentiation in architectural properties and functional traits of forest-floor saplings among heath, peat swamp, and mixed dipterocarp forests

There are physiognomically distinctive forest types in lowland tropics reflecting variation in edaphic conditions. Tree saplings that contribute to forest regeneration are expected to show morphological properties in response to forest environment. However, it remains unknown how sapling properties are similar or different across forest types. We examined architectural and functional traits of forest floor saplings across heath, peat swamp, and mixed dipterocarp forests that characterize lowland forests in Kalimantan, Indonesia. Saplings (150-310cm tall) of 41 species, which represent each forest type, were selected under the canopy of developed forest stands. Among these, we chose one species found in all forest types and two species in heath and peat swamp forests. Significant differences in crown allometries were found across forest types and across species. Saplings in mixed dipterocarp forest had thicker trunk and wider crown at the same sapling height compared to other forests and they had higher specific leaf area, higher mass-based leaf nitrogen content and lower wood density. Heath forest saplings showed lowest leaf nitrogen content and highest wood density. Species with across forest-type distribution showed intra-specific variation in sapling traits, and which was similar to the difference among forest types. We conclude that saplings show morphological response to nutritional and water conditions that characterize forest types. Keywords: allometry, Kalimantan, nitrogen content, specific leaf area, wood density Tropics, 2014, 22(4), 157-167.