Soil DNA from treatment code B1
The V4 variable region of the 16S rRNA gene was amplified using a pair of primers, 515F and 806R, linked to the barcodes and a Phusion high-fidelity PCR master mix (New England Biolabs, Ipswich, MA, USA). The PCR product was purified using a QIAquick gel extraction kit (Qiagen, Inc., Valencia, CA, USA). The amplified DNA library was constructed with a TruSeq DNA PCR-free sample preparation kit (Illumina, San Diego, CA, USA) and analyzed with a HiSeq2500 PE250 sequencing platform (Illumina, San Diego, CA, USA). Data of raw sequence reads was converted to fastq files. The fastq files were consecutively processed using the FLASH software version 1.2.11, the FASTP software version 0.20.1, the VSEARCH software version 2.21.1, and the QIIME2 software version 2021.4 to obtain the effective tags.