Figure 4.

Changes in bacterial pmoA gene copy numbers in soil microcosms incubated at 25 °C for 0, 14 and 28 days at low (15 μg NH₄⁺-N per g dry soil added initially; 7.5 μg NH₄⁺-N per g dry soil on days 7, 14 and 21) and high (150 μg NH₄⁺-N per g dry soil added initially; 75 μg NH₄⁺-N per g dry soil on days 7, 14 and 21) levels of ammonium as well as 0% and 1% methane in the headspace. Repeated methane addition every 3 to 4 days was started on day 14. Data plotted are mean values (n=2 or 3) and s.e. from nonlabeled microcosms destructively sampled at each time point.