Changes in fungal diversity and similarity along an experimental nitrogen gradient

Background/Question/Methods

Anthropogenic inputs of nitrogen into ecosystems could reduce biodiversity within affected systems, but responses could depend on the level of nitrogen inputs and duration of exposure. We examined the response of the soil fungal community using the long-term experimental nitrogen addition gradient at the Harvard Forest Chronic Nitrogen Amendment plots. We used the Illumina platform to sequence the fungal ITS rDNA marker, and quantified changes in the fungal community using taxonomic and phylogenetic measures of diversity and community similarity.

Results/Conclusions

We found that fungal phyla responded differentially to experimental nitrogen additions. Members of the Glomeromycota showing decreased diversity and increased community similarity at both intermediate and high levels of nitrogen input. In contrast, members of the Ascomycota and Basidiomycota showed a curvilinear response, where diversity increasd at intermediate levels of nitrogen addition, but declined at higher levels. The loss of taxa was non-random, such that specific clades appeared to be more sensitive to nitrogen additions. These findings suggest that nitrogen acts as a strong selecting factor that will likely restructure soil fungal communities.