Soils that have the aquic moisture regime are virtually free of dissolved oxygen because they are saturated by water. To have an aquic moisture regime, a soil must be saturated for at least a few days a year, because it’s implicit in the concept that dissolved oxygen is virtually absent. It is also implicit that the soil temperature is above biologic zero for some time while the soil is saturated, because dissolved oxygen is removed from ground water by respiration of micro-organisms. The level of ground water fluctuates with the seasons; it is highest in the rainy season or in fall, winter, or spring when cold weather virtually stops evapotranspiration. [1]
Udic