Effects of soil water regime and nitrogen addition on ectomycorrhizal community structure of Picea asperata seedlings

Abstract

Background Ectomycorrhizal (ECM) symbiosis is a fundamental driver in forest ecosystems. Studies of effects of fertilizer treatment on ECM fungal community structure were predominantly based on large, single additions of nitrogen. Studies involving chronic additions of nitrogen in combination with different gradients of water regime are much less common. Aim To investigate effects of water regime and nitrogen addition on the structure and diversity of ECM community, and identify main factors leading to changes in ECM community of Picea asperata. Methods The structure and diversity of the ECM community were assessed by Illumina high throughput sequencing analysis of the internal transcribed spacer (ITS) region of rDNA extracted from ECM root tips, after 5 years of different gradients of water regimes [40% (W1), 50% (W2), 60% (W3), 80% (W4) and 100% (W5) of field capacity, respectively] and nitrogen additions [0 (N0), 20 (N1), 40 (N2) g N m–2 y–1 by adding ammonium nitrate (NH4NO3) solution]. Results ECM community structure was altered by water and nitrogen treatments. Clearer separations were found under water treatment than under nitrogen treatment. ECM community species richness of N1 was significantly higher than that of N2 under W5 treatment and was significantly influenced by the interaction of water and nitrogen. However, the diversity and evenness of the ECM community were unaffected. Soil water content (SWC), nitrogen availability and their interaction, soil available phosphorus, and pH (which were induced by treatments) significantly explained the variation in ECM community structure among different treatments. Conclusion ECM species are more sensitive to changes in SWC than changes in nitrogen addition. Nitrogen and water treatments influenced the structure of the ECM community mainly through altering the relative abundances of exploration types and specific genera. Our findings can enhance understanding of the implications of nitrogen addition and water regime on soil processes in ECM‐dominated coniferous forests under global changes.