Effect of cellulose addition on bacterial and fungal communities in Ultisols

We conducted a microcosm experiment incubated soils that had been subjected to long-term mineral or organic fertilization with cellulose. Cellulose addition significantly reduced the alpha diversity of bacteria and fungi across all fertilization treatments, with a more pronounced effect observed for fungi. Moreover, cellulose addition strongly altered bacterial community structure by increasing the relative abundance of copiotrophic bacteria such as Actinobacteria and Proteobacteria while reducing that of oligotrophic bacteria (e.g., Chloroflexi). Compared with no-fertilizer treatment, the influence of cellulose addition on bacterial and fungal community structure was stronger in long-term mineral or organic fertilized soils. In addition, cellulose addition decreased soil microbial network complexity and the number of potential keystone taxa, but did not change the key role of Chloroflexi in soil microbial network. Overall, we demonstrated that cellulose addition decreased soil microbial diversity and network complexity, with possible negative consequences for ecosystem functioning in Ultsiols. This finding is important because it implicates that organic amendment in the short-term may have adverse impacts on soil ecosystem functioning.