Arable land plot 1 Capulin
The DNA was extracted from 0.25 g soil with PowerSoil® DNA Isolation Kit MoBio (Carlsbad, CA, USA) according to the procedure suggested by the manufacture. The region V1–V6 of the 16S rRNA gene from the metagenomic DNA was amplified by PCR with the following primers 8–F (5´–AGA GTT TGA TCI TGG CTC A– 3´) and 949–R (5´-CCG TCW ATT KCT TTG AGT T-3´) with 10 pb multiplexed and containing the Roche 454 pyrosequencing adaptors Lib–L (Navarro-Noya et al., 2013). All samples (n = 45) were amplified in triplicate, purified using UltraClean® PCR Clean-Up kit (MoBio Laboratories, Carlsbad, CA, USA) as recommended by manufacturer. Details of the PCR reactions can be found in Navarro-Noya et al. (2013). Quantifications of PCR products were performed using PicoGreen dsDNA assay (Invitrogen, Carlsbad, USA) and a NanoDropTM 3300 fluoroespectrometer (Thermo Scientific NanoDrop) and pooled in equal amounts. Sequencing was done by Macrogen Inc. (DNA Sequencing Service, Seoul, Korea) by using a Roche GS–FLX Plus 454 pyrosequencer (Roche, Mannheim, Germany).