NMDS analysis of SSU rRNA gene composition in non-fractionated DNA (colored points) indicates
that isotopic labelling does not alter overall microbial community composition,
microbial community composition in the soil microcosms changes over time, and
variance in non-fractionated DNA is smaller than variance in fractionated DNA (black points).
SSU rRNA gene sequences were determined for non-fractionated DNA from the
unlabeled control, $^{13}$C-xylose, and $^{13}$C-cellulose treatments over time (colors
indicate time, different symbols used for different treatments). Distance in SSU
rRNA gene composition was quantified with the UniFrac metric. The
leftmost panel indicates NMDS of data from both non-fractionated and
fractionated samples. The rightmost panel indicates NMDS of data only from
non-fractionated DNA. Statistical analysis is presented in main text. Samples not
represented in the ordination did not sequence successfully and constitute
missing data (e.g. ``12CCPS'' day 7).
