The secondary forest of Tanah Grogot, East Kalimantan, Indonesia
The Plant Diversity of Malesia
The mangrove forest occurring in the Apar Bay, Tanah Grogot is typical of the luxuriant mangrove forest developed in the coastal zone of East Kalimantan province. It has been declared a nature reserve and has an estimated area of about 128,000 ha. This mangrove forest consists mainly of pure stands of A vicennia ojjicinalis L. in the seaward zone and Ceriops tagal (Perr.) C. B. Robins in the landward zone, both of which grow on similar substrates. Soil samples from pure Avicennia and Ceriops
... nnia and Ceriops stands were analyzed in terms of their physical and chemical properties. All soils examined were weakly acidic, high in organic matter and low in available phosphorus. They were also characterized by high bulk density and moderate CEC (cation exchange capacity). The soils covered by the dominant species of Avicennia contained less sand and more silt than those covered by Ceriops. Generally, the soils covered by Avicennia were higher in pH (4.83±0.38 in H 2 0), CEC (23.72±O.70 meq/lOO g dry soil), exchangeable cation and NHcN (453.705±1.031 ppm), and lower in organic matter (6.81±0.14%) than those covered by Ceriops. The results suggest that Avicennia ojjicinalis L. and Ceriops tagal (Perr.) C. B. Robins grow well in their present substrates, as shown by their high biomass and stand density per 100m 2. The most extensive and luxuriant mangrove swamp forests in Kalimantan, Indonesian Borneo, are found in East Kalimantan province, where their total area is about 266,800 ha, or 69.58% of the total mangrove swamp forest in Kalimantan [Darsidi 1984J. The forests are well developed structurally and floristically along the coast, estuaries, deltas and small islands. Mangrove swamp forests in East Kalimantan province are among the most productive environments [Sukardjo 1993J. They provide tremendous economic benefits to mankind through fishery production (over two-thirds of East Kalimantan fish harvest is linked to the health of mangrove swamp forest areas), maintenance of the water table for agriculture, water storage and flood control.