Soils in the Mangrove Forests of the Apar Nature Reserve, Tanah Grogot, East Kalimantan, Indonesia

Abstract

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 Avicennia officinalis 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 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_2O), CEC (23.72±0.70 meq/100g dry soil), exchangeable cation and NH_4-N (453.705±1.031ppm), and lower in organic matter (6.81±0.14%) than those covered by Ceriops. The results suggest that Avicennia officinalis 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.