SOURCES AND SINKS OF METHANE AND CARBON-DIOXIDE EXCHANGES IN MOUNTAIN FOREST IN EQUATORIAL AFRICA

Sources and sinks of methane were studied in the Mayombe forest, a tropical evergreen forest located in a mountainous region in central Africa. Important methane emissions, reaching 6 x 10(13) molecules /cm2/s, were measured in flooded lowlands where soil characteristics: pH and redox potential, favor the growth of methanogenic bacteria. However, basically, soils of this region constitute a sink of atmospheric methane with uptake rates ranging from 10(10) to 10(11) molecules/cm2/s. Methane emission from termite nests was also studied; it appeared to be a minor component of the methane budget. CH4 concentrations were measured inside the forest and in the surrounding atmosphere, CO2 being used as a qualitative tracer of air exchanges. In spite of intense but scattered and size-limited sources this environment seems to be a net sink of atmospheric methane.