A methanotrophic community in a tropical peatland is unaffected by drainage and forest fires in a tropical peat soil

摘要

The effects of drainage and forest fires on the methanotrophic activity and community structure of peat soils in a tropical forest were studied by analyzing methane fluxes and the population of methanotrophs. A denaturing gradient gel electrophoresis (DGGE) analysis was used to target particular methane monooxygenase genes (pmoA). An incubation experiment was performed to investigate methane production activity relative to the effects of flooding and litter fall. Low levels of methane fluxes were observed in the soils in drained forest, natural forest and burned forest sites. These fluxes did not differ significantly among the sites (-0.02 +/- 0.01-0.36 +/- 0.30 mg C m(-2) hr(-1)). The water-filled pore space (WFPS) showed a statistically significant positive relationship with methane fluxes and a statistically significant negative relationship with the populations of methanotrophs. A DGGE profile targeted on pmoA gene fragments showed no apparent differences in the gene patterns among the various soil types. Four of the excised bands showed identical sequences closely related to type 1 methanotrophs, Methylomonas spp. An incubation experiment showed stronger methane oxidation than methane production in the absence of litter, even under flooded conditions. These results indicated that labile organic carbon or intact photosynthetic products, such as litter, may act as the principal substrate for methane production in the flooded condition and that the recalcitrant woody organic matter preserved under flooded anaerobic conditions in the peat soils for a long period would, most likely, play only a subordinate role. Under these environmental conditions, the methanotrophic community may consist primarily of type 1 methanotrophs irrespective of drainage and forest fires, and its activity could be controlled by WFPS by adjusting the oxygen supply to the peat soils