design: For soil sample of peatland mesocosms,  E.Z.N.A. DNA Kit for Soil (Omega Bio-tek,Norcross, GA, United States) was used to extract the microbial DNAfrom all mesocosms soil samples, following the given manual. 2%agarose gel was used to evaluate the quality of the DNA. The V4-V5region of the bacteria 16S ribosomal RNA gene was amplified by PCRusing forward primer 515F (5-barcode-GTGCCAGCMGCCGCGG-3)and 907R (5-CCGTCAATTCMTTTRAGTTT-3). The barcode is aunique eight base sequence for each sample. PCR mixture included of20L mixture comprising four L of 5FastPfu Buffer, 2L of 2.5mMdNTPs, 0.8L of each primer (5M), 0.4L of FastPfu Polymerase,and 10ng of template DNA. Agarose gel (2%) was used to extractamplicons that were purified by using AxyPrep DNA Gel ExtractionKit (Axygen Biosciences, Union City, CA, United States) according tothe manufacturers instructions and later Quantus Fluorometer(Promega, United States) was used to quantify them. The PCR products were quantified using Qubit3.0 (LifeInvitrogen), and amplicons (every 24) with different barcodes wereequally mixed. In addition, Illuminas genomic DNA librarypreparation procedure was used to construct the Illumina Pair-Endlibrary from pooled DNA at Shanghai BIOZERON Biotechnology Co.,Ltd. (Shanghai, China) on the NovaSeq PE250 platform.