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Title: METHANE OXIDATION AND PRODUCTION ACTIVITY IN SOILS FROM NATURAL AND AGRICULTURAL ECOSYSTEMS

Author
item CHAN, ALVARUS - IOWA STATE UNIVERSITY
item Parkin, Timothy

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2001
Publication Date: 11/1/2001
Citation: CHAN, A.S., PARKIN, T.B. METHANE OXIDATION AND PRODUCTION ACTIVITY IN SOILS FROM NATURAL AND AGRICULTURAL ECOSYSTEMS. JOURNAL OF ENVIRONMENTAL QUALITY. 2001. V. 30. P. 1896-1903.

Interpretive Summary: Methane is a potent greenhouse gas, therefore, it is important to understand the factors which contribute to the addition or removal of methane gas to or from the atmosphere. Some bacteria living in soil are capable of consuming atmospheric methane, while other soil bacteria can produce methane. Therefore, determination of whether a given soil is a source or a sink for methane depends upon the relative activities of these different groups of bacteria. Our study was designed to determine how agricultural practices influence the activities of methane producing and consuming bacteria in soil. Through laboratory incubations of soil from fields under a variety of agricultural practices, we determined that the activities of common methane consuming bacteria are decreased as compared to the bacteria in prairie and forest lands. This diminished methane consumption activity was related to the nitrogen levels in the soils. This information will aid scientists and policy makers in assessing the relative contribution of terrestrial ecosystems to the greenhouse effect.

Technical Abstract: Methane flux from soil is the result of two processes, methanogenesis and methane oxidation. Land use may have a profound impact on the relative activities of these groups of organisms. In this study, laboratory incubations were performed with soils collected from a variety of ecosystems including forest, prairie and agricultural systems. Methane production as well as consumption potentials were measured. Methane production potentials of most soils were low and in the range of 0.02 to 0.35 nMol CH4 g soil **-1 h**-1; however soils from two of the agricultural sites which experience periodic water saturation had CH4 production potentials in the range of 100 to 300 nMol CH4 g soil**-1 h**-1. The high methanogenic potential of these systems may indicate that CH4 oxidizers may not be wholly dependent on atmospheric CH4 for their survival and maintenance. Mean CH4 oxidation rates under ambient atmospheric CH4 concentrations (1.4 to 2 ul CH4/L) ranged from 2.8 to 91.1 pMol CH4 g**-1 h**-1 with the prairie ecosystems exhibiting the highest activity. Methane oxidation activity was markedly enhanced in soils incubated in an atmosphere enriched CH4 (10 ml/L), and rates ranged from 2.8 to 736 nMol CH4 g soil **-1 h**-1. This stimulated CH4 oxidation activity was greater in the agricultural soils as compared to the forest and prairie soils. Methane oxidation appeared to be related to nitrogen status (NO3**- and NH4**+) of the ecosystems. Under ambient atmospheric CH4 concentrations, CH4 oxidation was negatively related to soil mineral N (NO2**- + NO3**- + NH4**+) concentration.