Responses of soil fungal diversity and community composition to long-term fertilization: Field experiment in an acidic Ultisol and literature synthesis

Fungal communities play a critical role in regulating soil nutrient cycling and plant growth. However, the effects of long-term mineral and organic fertilization on fungal communities in Ultisols remain largely unknown. Soil samples from a 27-year fertilization experiment were used to investigate fungal communities through high-throughput sequencing along with literature data. The study involved seven treatments: no fertilization (Control), mineral NPK fertilizer (NPK), NPK fertilizer plus lime (NPK + Lime), NPK fertilizer plus peanut straw (NPK + PeanStraw), NPK fertilizer plus rice straw (NPK + RiceStraw), NPK fertilizer plus radish residue (NPK + RadResidue), and NPK fertilizer plus pig manure (NPK + PigManure). Long-term amendment of mineral and organic fertilizers did not alter fungal diversity in strong acidic Ultisols (original soil pH = 4.96). Metaanalysis of 60 global measurements in literature showed that fertilizer-induced decreases in fungal diversity (Hedge's d = - 0.36; p < 0.05) occurred mainly in soils with initial pH > 6 rather than < 6, potentially due to the decrease in soil pH in fertilized soils, with mineral fertilizers having stronger effects than organic amendments. Ascomycota was the dominant phylum in all treatments, accounting for 75-90% of the total sequences, followed by Basidiomycota (5.9-11%), which are consistent with data from literature. Application of NPK + Lime and NPK + PigManure shifted fungal community structure by increasing relative abundance of Hypocreales and Pezizales, respectively, compared with the Control, while amendment with NPK alone or in combination with crop residues did not. Soil organic carbon, effective diffusion coefficient of oxygen, and pH were the three most critical determinants of fungal community structure. Overall, our results suggest that fungal community structure rather than fungal diversity responded to the application of NPK + Lime or NPK + PigManure but not NPK + plant residues in WA Ultisols, and lack of response in fungal diversity to fertilization was potentially due to the particularly low soil pH in test soils.