title: Environmental sample from alvar grassland
design: Sampling was conducted in alvar vegetation in western Estonia. Sampling was conducted in July 2019 at 29 experimental sites. At each site, a randomly located 1  1 m plot was established. From each 1  1 m plot, a 5 g topsoil sample was collected from the corner. DNA was extracted from 5 g of dried soil using the PowerMax Soil DNA Isolation Kit and used to characterise the soil microbial community. The 16S rRNA gene was used to identify prokaryotes, the internal transcribed spacer (ITS) region was used to identify fungi, and the short fragment of the trnL (UAA) intron (the P6 loop, 10-143 bp) was used to identify plants. For prokaryotes, primers 515F and 926R were used to amplify the 16S rRNA variable V4 region; for eukaryotes, primers Euk575F and Euk895R were used to amplify the 18S rRNA region; and for plants primers trnL-g and trnL-h were used to amplify the short fragment of the trnL (UAA) intron (the P6 loop).