THE EFFECT OF CONTROLLED SOIL-TEMPERATURE ON DIEL CH4 EMISSION VARIATION

During the 1994 dry season, diel methane emission variations were moni tored in the greenhouse and the phytotron of the International Rice Re search Institute, Los Banos, Philippines at ambient and artificial soi l temperature regimes using a closed chamber technique. Diel soil temp erature regimes affected methane emission rates. Under ambient tempera ture regime, methane fluxes increased with rising soil temperature in the morning and reached a maximum in the early afternoon, then decreas ed rapidly and leveled off at night, while soil temperature declined g radually till sunrise next morning. Changing diel soil temperature reg imes resulted in changes in diel methane emission patterns irrespectiv e of the amplitudes of the methane emission rates. Using Arrhenius equ ation to simulate temperature dependence of methane emission variation s indicated that soil temperature is a major factor controlling diel m ethane emission variations (r(2) = 0.78). (C) 1997 Elsevier Science Lt d.