Figure 3.
Changes in gene ratios or relative gene abundances plotted together with selected geochemical parameters of the control and 10% (w/w) biochar-containing soil microcosms over time. Panel a shows N2O emissions in comparison with the ratio of nosZ over the sum of nirS and nirK gene copy numbers (nosZ/(nirS+nirK)). In panel b, ammonium concentrations are plotted together with the ratio of AOA over AOB (AOA/AOB ratio) as calculated from the bacterial and archaeal amoA gene copies numbers. Panel c shows ammonium concentrations and the relative abundance of nifH genes over total bacterial 16S rRNA genes. The small inserted graphs show a magnified view of the data for the first 8 days. Note that the y axes of the inserted graphs in panels b and c have a slightly different scale from the corresponding overview graphs. Open symbols with dashed lines represent data measured in the control microcosms without biochar. Filled symbols with solid lines represent data of the soil microcosms with 10% (w/w) biochar. Statistically significant differences (univariate ANOVA, post hoc: least significant difference) between control and 10% (w/w) biochar microcosms at a certain time point are indicated by lower-case characters above the individual data points (a=nosZ/(nirS+nirK), b=N2O, c=NH4+ and d=nifH/bacterial 16S rRNA genes).