Characteristics of Soil Temperature and Heat Flux within a Tropical Rainforest, Lambir Hills National Park, Sarawak, Malaysia

抄録

Soil temperature and heat flux were measured within a tropical rainforest, Lambir Hills National Park, Sarawak, Malaysia from March 2001 to April 2002. The vertical profile of soil temperature (-2~-50 cm depth) was measured by Copper-Constantan thermocouples at 4 different depths (-2, -10, -20 and -50 cm) and the soil heat flux was measured by a heat flow sensor at 10 cm below the forest floor. Clear seasonal variation was not seen in either temperature or heat flux. The daily range of soil temperature was the largest at the surface layer (-2 cm) and amplitude rapidly decreased with depth. The immutable layer (the highest layer of the daily temperature range < 0.1°C) of this study site estimated by the vertical profiles of the soil temperature was 41.35 cm below the forest floor. The daily range of soil heat flux was about ±5W/m², corresponding to less than 0.5 % of global solar radiation above the canopy. The soil temperature was highest in the surface layer during the period around noon; it was lowest during the period from midnight to early morning. According to the results of the soil heat conductivity analysis, it was suggested that the organic matter and water content were high within the upper soil layer (-10 cm depth). The estimated soil heat flux using a simple model was slightly higher for daytime and lower for nighttime than the observed levels. This discrepancy was assumed to be caused by the diurnal change of the soil water content in the upper layer.