Development and Vegetation Dynamics of a Lowland Ombrogenous Peat Swamp in Kalimantan Tengah, Indonesia

Abstract

The development and vegetation dynamics of an extensive Holo- cene lowland peat swamp from the Sebangau River near Palangkaraya in Kali- mantan Tengah, Indonesia, have been determined by means of a palynological study. From palynological analyses of six sediment cores taken along an 8 km tran- sect from the margin to the approximate geographical centre of the swamp it has been possible to assess both temporal and spatial changes of vegetation. Along the entire length of the transect, peat formation began abruptly over a topogenous eutrophic or mesotrophic swamp in which Gramineae and Lyco- podium cemuum were conspicuous elements. It is considered that this swamp may have existed under more seasonal climatic conditions than those which characterize the area today. Shallow peats probably bore a mixed swamp forest throughout their period of growth, whereas on deeper peats this gave way to a transitional community dominated by Dacrydium sp. and then to a true padang forest dominated by Combretocarpus rotundatus. During the latter phase of peat development the area witnessed a widespread invasion by Calophyllum retusum, this occurring quite independently of the swamp catena. This invasion may be analogous to the 'invasion fronts' some- times encountered in lowland dipterocarp forests. A comparison is made of the development of the Sebangau peats with the Marudi peat profile of Anderson & Muller (1975) from Sarawak. The major differences between the vegetation succession in the two areas relate to the nature of the substrate; the Marudi peats developed over mangrove, whereas those at Sebangau formed over a freshwater deposit. Evidence is presented to suggest that local river patterns have changed markedly during the course of the Holocene.