Nitrogen addition alters ectomycorrhizal fungal communities and soil enzyme activities in a tropical montane forest

- Oreomunnea mexicana is an ectomycorrhizal monodominant tree in tropical forest.
- We studied how increases in soil nitrogen affect ectomycorrhizal fungal communities.
- Nitrogen addition changes the relative abundance of ectomycorrhizal fungal genera.
- Nitrogen addition was associated with a reduction in soil enzyme activity.
- We observed lower ectomycorrhizal colonization in nitrogen addition plots.

Long-term increases in nitrogen (N) availability resulting from anthropogenic N deposition can strongly influence ectomycorrhizal (EM) fungal communities with potential consequences for nutrient cycling, forest composition and carbon storage. In a tropical montane forest in Panama, we used Illumina amplicon sequencing to examine how 9 y of experimental N addition has affected EM communities associated with Oreomunnea mexicana, and fluorescence assays to measure changes in enzyme activity in the soil. Nitrogen addition significantly reduced EM colonization of Oreomunnea roots and altered EM composition. The abundance of Laccaria and Lactarius increased with N addition, while Cortinarius declined. In addition, we found a reduction in soil phosphatase, N-acetyl-glucosaminidase, and β-xylanase activity with N addition. We conclude that a reduction in EM fungal taxa specialized in organic N and phosphorus absorption along with a decrease in EM colonization of host plants could decrease soil enzyme activity and therefore have feedback effects on soil nutrient cycling.