DNA extractions were performed using the DNeasy PowerLyzer Power Soil kit (Qiagen). PCR amplicon libraries targeting the V4 region of the 16S rRNA gene were generated using a barcoded primer set adapted for Illumina MiSeq, followed by paired-end sequencing. The primers (515FY/806RB) included sequencer adapter sequences, with 12 bp Golay barcodes incorporated in the reverse primer.