Microbial assemblages of coastal forested wetland soil promote growth of expanding shrub

Background and aims: Interactions with soil fungi impact plant performance and community assembly but can shift in direction and strength with changing abiotic conditions. In coastal wetlands, remote sensing has detected widespread landscape-level shifts from forest to shrubland, which are linked to saltwater intrusion and sea level rise (SWISLR). With SWISLR, forested wetlands experience canopy mortality that is preceded by shrub expansion into the understory. Methods: In this study, we explore whether plant-soil microbe interactions that differentially impact performance of woody species contribute to community shifts and lack of recovery of forests. In a greenhouse inoculation experiment, we assessed the performance of dominant coastal wetland tree and shrub species with forest and shrubland soil inoculations and tested the relationship between plant performance and soil fungal community composition and functional potential. Results: We found that inoculation with forest soil was advantageous to the more dominant invading shrub Morella, suggesting a microbial priming effect that facilitates shrub expansion. Employing a random forest regression model, we found that positive performance of Morella shrub in forest soils was associated with an increase in certain members of the Mortierellaceae. Plant performance was positively correlated with fungal richness, but not well-explained by the relative abundance of dark septate endophytes, saprotrophs, or pathogens. Performance was positively associated with mycorrhizal abundance for arbuscular mycorrhizal species, but not ectomycorrhizal species. Conclusion: Our findings highlight the importance of fungal assemblages in facilitating coastal wetland transition. Microbially-driven patterns may give expanding shrubs an advantage in forest soils prior to canopy die-off in the early stages of SWISLR.

Duke Scholars

Author Justin Prouty Wright Biology