Thirty four years of nitrogen fertilization decreases fungal diversity and alters fungal community composition in black soil in northeast China

• We assessed effects of long-term nitrogen fertilization on the fungal community structure.
• Fungal diversity and the number of ITS gene were affected by nitrogen fertilization.
• Fungal community composition differed between soils treated with higher and lower concentrations of nitrogen fertilizer.
• The influence of the more concentrated fertilizer treatments was greater than the lower concentrations.

Black soil is one of the main soil types in northeast China, and plays an important role in Chinese crop production. However, nitrogen inputs over 50 years have led to reduced black soil fertility. It is unclear how N affects the fungal community in this soil type, so a long-term fertilizer experiment was begun in 1980 and we applied 454 pyrosequencing and quantitative PCR to targeted fungal ITS genes. There were five treatments: control (no fertilizer), N1 (low nitrogen fertilizer), N2 (high nitrogen fertilizer), N1P1 (low nitrogen plus low phosphorus fertilizers) and N2P2 (high nitrogen plus high phosphorus fertilizers). Soil nutrient concentrations (Total N, Avail N, −NO3NO3−, +NH4NH4+, etc.) and ITS gene copy numbers increased, whereas soil pH and fungal diversity decreased in all the fertilized treatments. Relationships between soil parameters and fungal communities were evaluated. Dothideomycetes, Eurotiomycetes, Leotiomycetes, Sordariomycetes, and Agaricomycetes were the most abundant classes in all soils. Principal coordinates analysis showed that the fungal communities in the control and lower-fertilizer treatments clustered closely and were separated from communities where more concentrated fertilizers were used. Fungal diversity and ITS gene copy number were dependent on soil pH. Our findings suggested that long-term nitrogen and phosphorous fertilizer regimes reduced fungal biodiversity and changed community composition. The influence of the more concentrated fertilizer treatments was greater than the lower concentrations.