Riparian forest is a source energy and matter for the aquatic ecosystem. The abilities of riparian forest are to control and recycle the allochthonous inputs from the upland drainage basin and the river itself. This processess are a fundamental aspect of river ecology. We studied the riparian forest in karst ecosystem setting, at the protected forest of Sampolawa headwaters river, Baubau, Southeast Sulawesi. We focussed on the structure and composition of species richness of the forest. Data were collected using quadrate methods, 20mx20m, with 4 replicates placed at each river side. Results reveal that the forest compossed of 7 growth-forms, trees, saplings, seedlings, palm, herbs, liana, and spike moss. The tree species richness of tree and sapling was 33 and 37 species in consecutively. The tree species of Sphatolobus sp., Aglaia silvestris, and Canarium asperum dominated this riparian forest. Similarly the sapling dominance were Sphatolobus sp., Aglaia sp., and Chrysophyllum lanceolatum, as well as the seedlings of Sphatolobus sp., Palaquium obovatum and Chrysophyllum lanceolatum. Thus, the Sphatolobus sp. will be the future tree. However, Anthocephalus macrophyllus saplings were not found, thus this tree was endangered. Soil nutrients of NO3, NH4, PO4, and C organic were high, which indicated that the litterfall decomposition occurred at the forest riparian floor. The Riparian forest was a primary forest and very diversed in species richnes but had low densities. All the tree, sapling, and seedling species characterized the riparian forest of karst ecosystem at the headwaters of Sampolawa River in the karst ecosystem setting.

Keywords: Anthocephalus, karst-riparian forest, headwaters

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