This paper deals with the relation between soil respiration and some enviromental factors in a deciduous broad-leaved forest at Sanbe Forest of Shimane University.
1. The rate of soil respiration showed a seasonal change that has a peak at July, and the values of maximum were 9.89-11.38 CO_2g/m^2･day.
2. The soil respiration increased exponentialy with the increase of temperature, and the trend could be expressed by the following formula ; log Y=aT+b(Y:CO_2 g/m^2.day, T:temperature ℃, a and b:constant). In the case of air temperature as T, the formula of April to August that air temperature ascended was different from that of September to December that air temperature descended. The value of the constant "a" were 0.033-0.048 in the ascended period of air temperature larger than 0.029-0.045 in the descended period of air temperature. The value of the constan "b" differed by five plots, and were effective to the annual amounts of carbon dioxide evolved from forest soils. In the case of earth temperature as T, the formula did not differ by the periods. The value of constant "a" were 0.033-0.047.
3. The relation between soil respiration and water content were not closely as the relation to temperature, and the rate of soil respiration was the largest at 40-60 % of water content.
4. The annual amounts of soil respiration were 1969 CO_2 g/m^2･year in P-1,1719 in P-2, 1627 in P-3, 1888 in P-4 and 1943 in P-5.