Spatial and temporal variation in soil respiration in a Southeast Asian tropical rainforest

The influence of soil temperature and water content on soil respiration rate, and its spatio-temporal variation, were evaluated for a lowland dipterocarp forest in Peninsular, Malaysia. Soil respiration rate, temperature and water content were measured in a 50-m × 50-m plot with a nested sampling design of varying grid size. The variation in soil respiration rate increased with plot size. Geostatistical analysis indicated that the range of spatial autocorrelation for soil respiration rate and water content fell between 4.4 and 24.7 m. Spatially, the soil respiration rate was low where soil water content was high. In contrast, temporally, the soil respiration rate was low when the soil was dry. During dry periods, the soil respiration rate was still lower in wetter areas. These results suggest that a physical factor such as the restriction of gas diffusivity in water-saturated soil is not the primary cause of the low soil respiration rates in wetter places, and that several physical, biological and chemical properties co-varying with soil water drive the bipolar spatial and temporal variation of soil respiration rate.