Soil bacterial diversity under nitrogen and water addition
We use nitrogen fertilizer and irrigation to simulate the effects of nitrogen deposition and precipitation on soil bacterial diversity in Stipa baicalensis steppe of northern China. Split-plot design was used in our experiment. The main plots were water added and no water added respectively. N was added in the form of NH4NO3 at rates of 0、15、30、50、100、150、200、300 kg N• ha-1• yr-1. The soil sampling was conducted on 16 August 2013 by collecting ten randomly positioned, 0–20cm soil subsamples using a soil probe from each of the experimental plots. A total of 96 soil samples were collected from experimental plots. Bulk community DNA was extracted from each soil using the E.Z.N.A. Soil DNA Kit (OMEGA) according to the manufacturer’s instructions. Three DNA extractions per sample were conducted and then amplified with the primer pair 341f/805r. Samples were then pooled at equal concentrations. Sequencing of the amplicons was performed using Illumina Miseq according to the manufacturer’s instructions.