CH4 oxidation capacities and microbial community structures developed in response to the presence of CH4 were investigated in two types of landfill cover soil microcosms, waste soil (fine material in stabilized waste) and clay soil. CH4 emission fluxes were lower in the waste soil cover over the course of the experiment. After exposure to CH4 flow for 120 days, the waste soil developed CH4 oxidation capacity from 0.53 to 11.25-13.48 mu mol CH4 g d.w.(-1) h(-1), which was ten times higher than the clay soil. The topsoils of the two soil covers were observed dried and inhibited CH4 Oxidation. The maximum CH4 oxidation rate occurred at the depth of 10-20 cm in the waste soil cover (the middle layer), whereas it took place mainly at the depth of 20-30 cm in the clay soil cover (the bottom layer). The amounts of the phospholipid fatty acid (PLFA) biomarks 16:1 omega 8c and 18:1 omega 8c for type I and II methanotrophs, respectively, showed that type I methanotrophic bacteria predominated in the clay soil, while the type II methanotrophic bacteria were abundant in the waste soil, and the highest population in the middle layer. The results also indicated that a greater active methanotrophic community was developed in the waste soil relative to the clay soil. (C) 2008 Elsevier Ltd. All rights reserved.