METABOLIC AND ENVIRONMENTAL CONTROL ON METHANE EMISSION FROM SOILS: MECHANISTIC STUDIES OF MESOTROPHIC FEN IN WEST SIBERIA NICOLAI S. PANIKOV 1,2∗ , SVETLANA N. DEDYSH 2 , OLEG M. KOLESNIKOV 2 , ALLA I. MARDINI 2 and MARIA V. SIZOVA 1,2 1 Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ, U.S.A.; 2 Institute of Microbiology Russian Academy of Sciences, Moscow ( ∗ author for correspondence, e-mail: npanikov@stevens-tech.edu; fax: 201 216 8196) (Received 7 July 2000; accepted 31 January 2001) Abstract. The biological mechanisms regulating methane emission from natural wetlands are the fo- cus of this article. A novel technique provides estimates of the distribution of CH 4 sources within an undisturbed soil profile by recording the transient gas dynamics after soil enclosure by deep (50 cm) chamber. The combined use of conventional surface and soil chambers across a 200-m fen transect allowed us to relate the observed methane emission to its instant generation and uptake. Surprisingly, the methane generation was relatively constant (9–12 mg CH 4 -C hr -1 m -2 ) and highly variable net emission (0.2–20 mg CH 4 -C hr -1 m -2 ) was closely correlated (r = –0.809) with methane uptake. In laboratory incubations, CH 4 uptake followed Michaelis-Menten kinetics. Added chloride and nitrate irrespective of the cation’s nature suppressed uptake as a strong noncompetitive inhibitors (K i ∼0.5 mM). The methane formation turned out to be unstable and under anaerobic incubation, the formation of CH 4 , CO 2 and H 2 displayed sustained weekly oscillations. We conclude that effects of environmental factors alone are not sufficient to predict the variation in emission, which depends also on metabolic control of respective soil organisms. The multitude of such controls is dependent on diversity of respective soil organisms and could be grouped into a limited number of categories considerably simplifying large-scale simulations. Keywords: competitive, emission, inhibition, methane production and uptake, methane sources and sinks, noncompetitive, soil profile, sustained oscillations 1. Introduction Methane is an important green house gas affecting the heat balance at the Earth’s surface. Considerable efforts have been paid recent decade to interdisciplinary studies of methane emission to atmosphere as dependent on environmental factors, estimation of source/sink strength, understanding the basic underlying mechanisms and construction of the realistic and robust models able to predict future methane dynamics (Whalen and Reeburgh, 1988; Harris et al., 1993; Fowler et al., 1995; Hein et al., 1997; Matthews and Fung, 1987). Most of the known models describing methane emission belong to the category of semi-empirical models (Schimel and Panikov, 1999), which contain both mech- anistic terms and arbitrary expressions without clear physical/biological meaning. Water, Air, and Soil Pollution: Focus 1: 415–428, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.