Studies of peat swamps in Sarawak with particular reference to soil-forest relationships and development of dome-shaped structures

Tie, Yui-Liong (1990) Studies of peat swamps in Sarawak with particular reference to soil-forest relationships and development of dome-shaped structures. Doctoral thesis, Polytechnic of North London.


The main objectives of the study are to investigate the soil-forest relationships and to examine the development of the dome-shaped morphology of the peat swamps in Sarawak.

Physical constraints confined sampling to only 11 transects with 58 cases. Besides pedological and vegetation investigations, the study also involved radio-carbon dating, and monitoring of litterfall, decomposition rate and water-table fluctuation.

Almost all the nutrient elements show a surface concentration indicating the effect of the standing vegetation. Below the topsoil, the degree of decomposition and the levels of most nutrient elements show a decreasing trend down the profile. The trend is reversed as the mineral substratum is approached due to the effect of the latter.

In spatial terms, the change from the floristically rich, high volume Phasic Community at the periphery (PC 1) to the low stature, floristically poor forest at the centre (PC 6) is reflected by a general decreasing trend of most nutrient elements in the surface peats. Discriminant analyses show that this forest zonation across the peat dome is mainly associated with the peat materials becoming less decomposed and having higher particle densities but lower levels of calcium, phosphorus, iron and copper, from PC 1 to PC 6.

It is shown that the initial formation of lowland peats in Sarawak took place under low-lying, poorly drained but largely terrestrial conditions rather than an aquatic situation with a permanent water body. As successive layers of peat in the shape of an inverted saucer were accumulated, the deposit grew vertically and laterally. As the peat at the centre got thicker, the rate of growth decreased as a result of lower soil fertility due to leaching and therefore lower biomass production. This allowed the adjacent areas to catch up and form the flat-topped structure. At the same time, the periphery steepened because the net rate of growth at the very edge also decreased due to a higher rate of decomposition.

It is also suggested that agricultural development, where necessary, should best be confined to the fringes of the peat dome with PC 1 and 2; PC 3 may be considered for silviculture with proper management, while PC 4 to 6 should be kept under the natural conditions.

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