Plant-soil-feedbacks can have both positive and negative effects on plants depending on the type of microbes, like pathogens, symbiotroph, or saprotrophs, they promote in soils. This relationship is mediated, in part, by a plant’s mutualism with mycorrhizal fungi. Generally, arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) associations are thought to have different effects on the community dynamics of plant-soil-feedbacks, yet empirical evidence for the microbial community responses to these different mycorrhizal types is limited. We performed two field experiments in montane rainforests in western-Panama on the effects of AM vs EM mycorrhizal trees on surrounding fungal communities, particularly the relative abundance of pathogens, symbiotroph, and saprotrophs. In both experiments, soil DNA extracted from the top 10 cm of soil was sequenced via Illumina sequencing and processed using various bioinformatic techniques including FUNGuild to assign functional groups. The first experiment compared soils in monodominant EM plots to those in near-by mixed-species plots, the second compared soils close to AM and EM trees within mixed-species plots.
Results/Conclusions
Fungal communities were relatively consistent across EM plots and trees but were diverged in mixed plots and near AM trees. Further, the relative abundance of pathogenic and saprotrophic fungi was significantly greater in mixed plots than in EM plots and within mixed stands pathogens had lower relative abundance near EM trees than AM trees. These results show a strong relationship between mycorrhizal types and plant-soil-feedbacks of surrounding fungal community composition, potentially helping explain how EM trees can form monodominant stands and influence ecosystem processes.