Temperature and Moisture Controls of Soil Respiration in a Dry Dipterocarp Forest, Ratchaburi Province

To quantify soil respiration and to investigate its diurnal and seasonal variations, soil respiration was studied in a dry dipterocarp forest located in Chombung District, Ratchaburi Province (13° 35’ 13.3” N, 99° 30’ 3.9” E). Soil respiration was measured hourly during February to July 2008 using a closed-automatic chamber method. The results showed that soil respiration varied significantly both spatially and seasonally. Among three replicates of measurements and within each hour of measurement, the coefficient of variations could be as high as 80%. On a daily scale, a weak relationship between soil respiration and soil temperature was observed. On a seasonal scale, a negative relationship between soil respiration and temperature was observed. However, a strong positive relationship between soil respiration and soil moisture over the moisture range of 17-19%vol was found. Soil respiration decreased beyond this moisture level. The total CO2 emissions during the six-month period in dry dipterocarp forest were 1.81 kgCO2/m 2 , or 4.9 tonne C/ha.