Inoculating rhizome-propagated Sporobolus pumilus with a native mycorrhizal fungus increases salt marsh plant growth and survival

Abstract

Salt marshes are ecosystems of significant ecological importance for coastal stability and fundamental roles in marine ecosystems. Salt marshes are declining due to anthropogenic and natural causes including sea level rise. Coastal restoration efforts have increased worldwide, but many fail in long-term coastal stability. We used a naturally occurring arbuscular mycorrhizal fungus (AMF) to test whether survival and early growth of the salt marsh grass Sporobolus pumilus (formerly Spartina patens) improved under simulated salt marsh conditions. Using a tidal mesocosm bench, we grew inoculated plants with varying AMF treatments under simulated tidal regimes to determine if AMF could aid in establishment of healthy Sporobolus communities. Rhizome-derived S. pumilus had greater survival and grew faster than seed-derived plants. Plants inoculated with propagated AMF consistently outperformed both sterile and native sediment controls in terms of plant survival and growth. Use of rhizome-derived Sporobolus inoculated with propagated Funneliformis geosporum showed the most promise in producing successful plant populations for salt marsh restoration. This may be due to plant life stage and improved plant nutrient status, allowing rhizome-derived plants to grow more quickly than seed-derived plants. Using these plants in future large-scale restoration may increase re-establishment of salt marsh ecosystems.

Specificity in plant-mycorrhizal fungal relationships: prevalence, parameterization, and prospects

“…The Driver Hypothesis proposes that AM fungi are a key driver in maintaining and explaining plant diversity by selective association with plants and by doing so they shape the aboveground plant communities (Hart et al, 2001). Some support comes from studies showing plants with stronger associations with AM fungi have higher survival rates and are more competitive in nutrient-poor soils (Johnson et al, 2003;d'Entremont et al, 2021a), while others have shown that AM fungi can increase plant diversity by increasing the total number of species that can coexist in a given area (Van Der Heijden and Scheublin, 2007). In contrast, the Passenger Hypothesis proposes that although AM fungi are important for plant growth and survival, they do not play a significant role in regulating plant diversity or community composition and that plant community composition has control over this interaction (Grman, 2012).…”