How methane feedback response influence redox processes in a tropical vertisol

It has been predicted that soil CH4 consumption potential will increase due to rise in concentration of atmospheric CH4. However, it is unclear how this altered activity of soil will influence soil biogeochemical processes. Experiments were carried out to examine the effect of CH4 feedback response on (1) CH4 consumption potential, (2) population dynamics of methanotrophs, and (3) reductive biogeochemical processes in a tropical vertisol. Soils of different CH4 consumption potentials were prepared by three CH4 feeding cycles. Soils were then incubated to determine terminal electron accepting process (TEAPs) comprising sequential reduction of terminal electron acceptors (NO3 (-), Fe3+, SO4 (2-), and CO2). Diversity of methanotrophs was estimated by terminal restriction fragment length polymorphism (TRFLP) targeting the pmoA gene. Methane feedback increased apparent CH4 consumption rate (k) from 0.49 to 1.09 mu g CH4 consumed per gram of soil. Potential denitrification rate (PDR), potential iron reduction rate (PIR), potential sulfate reduction rate (PSR) increased with k (p < 0.0001). Abundance of methanotrophs and heterotrophs was positively and significantly correlated with k (p < 0.0001). Methane feedback cycle influenced composition of the methanotrophs community (p < 0.0001). Principal component analysis (PCA) explained 83.86 and 12.05 % of variation by first two components.