Hydraulic conductivity and moisture characteristics of tropical peatland-preliminary investigation

Abstract

The hydrological condition and its related moisture characteristics of the soil are important factors contributing to forest and plant growth in peatland ecosystem. These hydrological characteristics would also provide an indirect view point of the current management practices in the case of land cover other than natural forest. This paper reports our recent research findings on the behavior of field hydraulic conductivity (K) and moisture characteristics of peatlands typically found in Sarawak. The field hydraulic conductivity measurements were carried out on different forest types, namely mixed peat swamp, Alan forest and Padang Alan forest in the virgin peat swamp forest at Loagan Bunut National Park using auger hole and pumping method.. The moisture characteristics of peat materials were obtained from samples taken from different areas in Sarawak representing different degrees of peat decomposition under various agronomic practices. The moisture characteristic determination was conducted in the laboratory using a combination of sand/kaolin box for suction pressure less than 500 cm (pF<2.7; < 0.5 bar) and pressure membrane apparatus for 500-15000 cm (pF 2.7-4.2 or 0.5-15 bar). Peat materials from different ecosystems behaved differently in terms of its hydraulic conductivity. The hydraulic conductivity values depended on the hydraulic gradient and the degree of decomposition of peat. Generally, the higher the hydraulic gradient, the greater the K value. This implies that under shallower water table, the drainage process would occur slower thus more favorable to plant growth through maintaining the soil moisture status. However, it would also imply the higher likelihood of flooding. The K value was directly proportional to the degree of decomposition.