LB 29-247 - Evaluating plant-microbe associations in response to environmental stressors to enhance wetland restoration

Microorganisms can enhance nutrient acquisition or suppress diseases from pathogens, while plants can provide carbon resources and oxygen to root-associated microbes. However, human activities have changed nutrient cycles and disrupted mutualisms. Therefore, we need to understand how to promote positive plant-microbe associations to aid in restoring coastal wetland ecosystems where human stressors (e.g., nutrient pollution) and climate change (e.g., hurricanes, sea-level rise) challenge restoration outcomes. We examine how nutrient/salinity stressors influence plant-microbe relationships. We hypothesize that the presence of microbes will buffer stressor (nutrient/salinity) effects. We used a simplified soil bacterial isolate approach and a whole sediment inocula approach to test this hypothesis. First, we conducted a factorial experiment, where Chasmanthium laxum seedlings were combined with bacterial isolates (cultured from fertilized or unfertilized wetland soils or no bacteria control) along a nutrient gradient at five levels ranging from 0x-2x the amount of fertilizer applied in the field. After three months, we harvested, dried, and measured plant biomass. Results showed that aboveground plant biomass was highest at low fertilization (0-0.5x) when bacterial inocula were sourced from unfertilized compared to fertilized soils, but biomass was similar across inocula sourced at 1-2x nutrient addition. Second, we collected Spartina alterniflora seeds from coastal salt marshes. We set up a replicated factorial experiment with two levels of microbiome addition (+microbe, no microbe) and two levels of salinity (0 psu, 35 psu) replicated five times. We pre-treated seedlings by combining microbial inocula from the marsh site with autoclaved soilless media and exposed half the samples to salt water (35 psu) and half to freshwater (0 psu). Results revealed that microbial inocula additions during early plant development could be critical for establishing stress-tolerant seedlings for transplanting into marsh restorations. This work provides evidence that microbial stewardship is important for buffering against environmental stressors and could promote plant establishment for wetland restoration.