The abundance and distribution of rattan over an elevation gradient in Sulawesi, Indonesia
Forest Ecology and Management
The rattan flora of Central Sulawesi is abundant, species rich and patchily distributed in lowland and montane forests. I recorded the abundance and distribution of rattan on five randomly established 10 m X 1000 m transects between 830 and 1330 m elevation and associated changes in forest canopy heights, photosynthetically active radiation (PAR) and soil characteristics. Rattans were observed at all sites and elevations (100% of 10 m X 10 m sample plots in the transects contained rattan), but exhibited the greatest diversity (species richness) between 1180 and 1280 m elevation. Overall (all species and elevations), there was an average of 314 mature rattan genets per hectare. The two most prominent rattans in terms of size, abundance and distribution, Calamus zollingeri and Daemonorops robusta, averaged 62 and 40 genets/ha overall, respectively. Several other rattans, including C. leiocaulis, C. leptostachys, and C. ornatus occurred on all transects and all elevations. In contrast, C. didymocarpus, C. minahassae, C. symphysipus and Korthalsia celebica were patchily distributed, and C. didymocarpus and C. sp. ('kalaka') were restricted to higher elevations. Resident cane collectors differentiate C. zollingeri and D. robusta into low and high elevation forms on the basis of morphological and growth characteristics, but this distinction is not discernable in sterile specimens. Based on local classification, lowland forms of C. zollingeri and D. robusta were replaced by high elevation forms over less than 200 m vertical elevation which corresponds to the transition from upper lowland to montane forests. The mean canopy height of upper lowland forest between 900 and 1000 m was significantly greater than that of montane forests between 1100 and 1300 m (30.0 and 21.2 m, respectively). Soils in upper lowland forests had significantly higher concentrations of NO3 and P, significantly lower organic matter levels and higher pH than montane soils in both O and A/E soil horizons. PAR levels did not vary significantly by forest type. Most large diameter rattans are marketed under a single trade name and cannot be distinguished by cane characteristics. These findings have significance for biodiversity conservation and management because rattan harvesting is widespread and unmanaged, and the Sulawesi rattan flora remains poorly known taxonomically and ecologically.