Fig. 5

Estimated abundance of in situ microbial genes in Bawburgh (B) and Wytham (W) soils using synthetic spikes. Abundance in soil was calculated as follows: microbial rRNA abundance = (number of microbial-origin reads/number of synthetic-origin reads) × synthetic spike copies added to sample prior to DNA isolation for 16S rRNA with P synthetic spike, 18S rRNA with E synthetic spike and ITS with F synthetic spike. Gene copy number per gram soil on the y-axis is plotted against synthetic spike level (1–8, Table 1) on the x-axis