Variations in microbial activity due to fluctuations in soil water contentat the water table interface

A soil column experiment was designed to investigate the response of an ind igenous microbial population to a vertically fluctuating water table. A sub surface environment with a transitional zone was simulated. The water table in the soil columns was raised and lowered, and compared to columns under static conditions. Carbon dioxide and oxygen concentrations were measured. Peaks of CO2 occurred in the fluctuating columns immediately following a ri se in the water table. Dissolved O-2 in the fluctuating columns was consist ently lower throughout the experiment, but these lower concentrations were exaggerated immediately following a rise in the water table. Values for tot al organic carbon in the pore water were slightly lower in the fluctuating columns. The results of this soil column study indicate that vertical fluct uation of the water table can enhance microbial activity of indigenous soil microbial populations. This increase in microbial activity suggests an inc reased rate of available carbon under these conditions.