Spatial and temporal variations in soil respiration hot spots in a lowland tropical rain forest, Peninsular Malaysia

Many studies have reported the presence of soil respiration hot spots, which are areas of extremely high soil respiration, but little is known about their causes. Because previous studies implied that they were caused by macrofauna, we conducted a field survey in a Malaysian lowland rainforest to examine whether increased soil respiration was induced by the activities of macrofauna such as termites, ants and earthworms. Soil respiration was measured in a grid system of 10 m intervals in a 1 ha plot. We measured soil respiration again three or four days after the first measurement to examine the spatiotemporal change in hot spots. After the second measurement, we excavated soil to a depth of 20 cm at the five points showing the highest soil respiration rates (hot spots) and their neighboring points as controls and visually searched for macrofauna. The average soil respiration for two measurements did not differ significantly (8.21 and 7.93 mu mol CO2 m(-2) s(-1), respectively). Four hot spots were revealed in each of the two measurements, but only one appeared in both measurements. Several ants (100-500 individuals, Lophomyrmex sp.) were observed in soil under soil respiration chamber areas at one hot spot and one control point, respectively. This suggests that the hot spots in the study site were not located near active nests or intensively active areas of macrofauna, and it is possible that the hot spots may represent the points of mass CO(2)flux transport events.