design: We used the primer sets 515F/806R and ITS1F/ITS2R 109 to amplify a portion of the bacterial 16S rRNA gene and fungal ITS1 region, respectively. Extracted DNA was PCR-amplified using barcoded primer pairs to permit multiplexing using primers targeting the hypervariable V4 region of the 16S rRNA bacterial gene 109 and barcoded primer pairs targeting the fungal internal transcribed spacer region 109. PCRs were prepared in duplicate in 25 L reaction volumes consisting of 10 L Platinum Hot-Start PCR Master Mix (Invitrogen, Carlsbad, CA, USA), 11 L PCR H 2O, 1 L of each 10 M primer, and 2 L of template DNA. PCR cycling conditions were at 94C for 3 min, followed by 35 cycles of 94C for 45 s, 50C for 1 min and 72C for 1:30 min with the final extension step at 72C for 10 min. All samples were normalized using the Quant-IT PicoGreen dsDNA Assay Kit (Invitrogen, Carlsbad, CA, USA) and pooled by plate in equimolar concentrations to 150ng.  Plate pools were cleaned with MinElute PCR Purification Kit (Qiagen) and pooled equimolar to yield a  4 nM library for sequencing. Pooled libraries were sequenced on separate Illumina MiSeq runs (Illumina, California, USA) using a 2  250bp cycle kit at the Center for Microbial Exploration at the University of Colorado Boulder. We included associated blanks to identify potential contaminants in our pipeline.