Published online by Cambridge University Press: 23 February 2017
Experiments were carried out to determine methane (CH4) consumption in different soil (vertisol) aggregates under elevated carbon dioxide (eCO2) and temperature. Soil aggregates of <0·25 mm diameter (microaggregates), 0·25–1 mm diameter (mesoaggregates) and 1–2 mm diameter (macroaggregates) were incubated under different CO2 (400, 800 and 1200 µm/m or ppm CO2) and temperature (25, 35 and 45 °C) conditions. Methane consumption was high in mesoaggregates and low in microaggregates under ambient CO2 and temperature (25 °C). However, eCO2 and temperature significantly inhibited CH4 consumption and decreased culturable microbial numbers. Methane consumption in mesoaggregates was inhibited by 21–66% at 800–1200 ppm of CO2. Principal component analysis designated soil aggregate size as the most important component of variation, followed by temperature and CO2. Ordination biplot indicated eCO2 and temperature impacted negatively on CH4 consumption and culturable methanotrophs. Results highlighted that mesoaggregates of 0·25–1·00 mm are hotspots for CH4 consumption and that rising atmospheric CO2 and temperature may inhibit CH4 consumption significantly in a tropical vertisol.