Methane oxidation and production activity in soils from natural and agricultural ecosystems

Methane (CH(4)) flux from soil to the atmosphere is the result of two microbial processes, methanogenesis and CH(4) oxidation. Land use may have a profound impact on the relative activities of these groups of organisms. In this study, the CH(4) production and consumption potentials of soils from agricultural and nonagricultural ecosystems were assessed in laboratory incubations. Methane production potentials of most soils were low and in the range of 0.02 to 0.35 nmol CH(4) g soil(-1) h (-1); however, soils from two of the agricultural sites that experience periodic water saturation had CH(4) production potentials from 100 to 300 nmol CH(4) g soil (1) h (-1). The high methanogenic potential suggests that CH(4) consumers may not be wholly dependent on atmospheric CH(4) for their survival and maintenance. The prairie soils exhibited the highest CH(4) oxidation under ambient atmospheric CH(4) concentrations, and CH(4) oxidation activity was markedly enhanced in incubations with an atmosphere enriched in CH(4). This stimulated CH(4) oxidation activity was generally greater in the agricultural soils as compared with the forest and prairie soils. Methane oxidation appeared to be related to soil nitrogen status. Under ambient atmospheric CH(4) concentrations, CH(4) oxidation was negatively related to soil mineral N (NO(2)(-) + NO(3)(-) + NH(4)(+)) concentration. However, a positive relationship between soil mineral N status and CH(4) oxidation activity was observed in incubations with atmospheres enriched in CH(4). This pattern suggests that the agricultural lands contain different populations Of CH(4) oxidizers than the natural systems.