Fungal residues were more sensitive to nitrogen addition than bacterial residues in a meadow grassland soil

Fungi are more sensitive to long-term nitrogen addition than bacteria.Long-term nitrogen addition significantly reduces fungal biomass, but promotes the accumulation of fungal residues in soil.Long-term nitrogen addition has no significant impact on bacterial biomass and residues.Nitrogen (N) addition can significantly affect the amount of soil carbon (C) pools through biological routes, and microbial residues are important components of soil carbon pools. However, it remains unclear how N addition affects the accumulation of soil microbial residues in meadow grasslands. This study analyzed the effects of N addition on microbial residues in a meadow grassland soil, and the key factors affecting the accumulation of microbial residues under N addition were analyzed in combination with soil physicochemical properties and microbial community structure. The results showed that N addition significantly changed the structure of the microbial communities and the accumulation of microbial residues, mainly manifested by a significant decrease in fungal biomass and the fungal/bacterial ratio (F/B), but had no significant effect on bacterial or total microbial biomass (PLFAs). N addition significantly increased the accumulation of fungal residues (7.45%), but had no significant effect on the accumulation of bacterial residues or total amino sugar (TAS). We found that fungal residues were more affected by soil environmental factors than bacterial residues. The results of the random forest analysis showed that bacterial biomass under N addition was the most important predictor of soil bacterial residues, whereas total N (TN), pH and F/B were the most important predictors of soil fungal residue. In summary, our results indicate that fungal communities and residues accumulation play important roles in regulating the response of grassland soil C to N addition, further enhancing our understanding of the mechanisms of soil carbon pool to N addition.