Shifts in understory plant composition induced by nitrogen addition predict soil fungal beta diversity in a boreal forest

Aboveground-belowground interactions are important drivers of terrestrial ecosystem structure and function. However, changes in soil microbial diversity caused by shifts in the plant community composition in the context of nitrogen (N) deposition remain poorly understood in boreal forests. Based on a long-term experiment of N addition at rates of 0, 20, 50, and 100 kg N ha(-1) year(-1) in a boreal forest in northeastern China, we found that N addition resulted in an increasing dissimilarity in understory plant community composition along the elevated N addition rates. N addition had no effects on the soil microbial alpha diversity but did alter the soil microbial beta diversity. The shifts in the soil bacterial beta diversity following N addition were correlated with soil pH, whereas the changes in the soil fungal beta diversity were explained by changes in the understory plant composition. Since soil fungi play an irreplaceable role in boreal forests, our findings imply that N deposition-induced changes in understory plant community structures might be associated with changes in soil fungal community composition, with potential profound consequences on soil nutrient dynamics and soil carbon cycling.