DNA-seq of AM fungi
The genomic DNA was extracted from 0.25 g frozen soil samples using a PowerSoil DNA Isolation Kit. The V4 region of the 18S rDNA gene was amplified using a two-step PCR, and primer pairs GeoA-2 (Schwarzott and Schler, 2001) / AML2 (Lee et al., 2008) and NS31 (Simon et al., 1992) / AMDGR (Lumini et al., 2010) were used in the first and second PCR reaction, respectively. The primer NS31 was labeled with a unique 12 nt barcode at the 5end to discriminate different samples. The detail information about the PCR conditions and quality assessment can be found in Yang et al. (2020). The PCR products were purified, thoroughly mixed and sequenced at the Environmental Genome Platform of Chengdu Institute of Biology, Chinese Academy of Sciences.