Plant diversity and nitrogen addition affect the architecture of plant–soil–microbe stoichiometric networks

Background and aims Nitrogen enrichment and biodiversity affects the stoichiometry of plants, soils, and soil microbes. However, combined effects of nitrogen addition and biodiversity on interactions among the stoichiometry of plants, soils, and soil microbes (stoichiometric networks, PSMNs) have largely been overlooked, even though PSMNs are likely critical predictors of ecosystem structure and functions. Methods To quantify effects of nitrogen addition and plant species richness on stoichiometric relations among plants, soils, and soil microbes, a common garden experiment with two nitrogen addition levels (0 and 6 g N m − 2 year − 1 ) and four plant species richness levels (1, 2, 4, and 8 species) was conducted in which those driving factors were manipulated. Results Nitrogen addition had minor effects on most stoichiometries of plant–soil–microbes, but plant species richness showed significant association with most stoichiometries. With nitrogen addition, increases in soil ammonium nitrogen led to a decrease in PSMNs connectivity but an increase in modularity. Plant species richness was negatively associated with network connectivity but positively correlated with modular complexity because of changes in soil nutrient availability and increased niche differentiation. Conclusions The findings demonstrate mechanistic links of biodiversity with the stoichiometry of plant–soil–microbes and stoichiometric networks, suggesting that biodiversity loss and resources decrease under global changes may enable a looser complexity in whole ecosystem element structure as indicated by the stoichiometric network architecture.