Search for: All records

Abstract Despite substantial contributions of ecosystem services, mutualistic plant-microbe associations in wetlands are severely threatened by human activities. Therefore, promoting positive plant-microbe associations underpins coastal wetland restoration, where human stressors and climate change challenge successful outcomes. This study examined how salinity stressors influence plant-microbe relationships, where we hypothesized that the presence of marsh microbes would provide a rescue effect by buffering abiotic stressors and yielding higher plant biomass. We used a whole sediment inocula approach and exposed marsh cordgrass (Sporobolus alterniflorus) plugs to a factorial experiment with three levels of microbiome addition (microbial inocula, autoclaved microbial inocula, no microbe control) and two levels of salinity (< 0.5 psu, 20 psu), replicated ten times. We added marsh-site microbial inocula with autoclaved peat-based greenhouse soil and exposed half the plugs to saltwater (20 psu) and half to freshwater (< 0.5 psu). Results revealed that marsh microbial inocula additions during early plant development may ameliorate salinity stressors. Plants treated with microbial inocula and salinity stress exhibited greater aboveground biomass (P < 0.09) than those under freshwater conditions. With live microbial inocula, the median of aboveground biomass and change in plant height were higher in saltwater compared to freshwater conditions. Change in plant height, belowground biomass, root-to-shoot ratio, soil bacterial diversity H’, and evenness J’ were similar across microbial and salinity treatments. However, salinity (P < 0.001) and microbial treatments (P < 0.001) significantly influenced the bacterial community composition, with distinct assemblages under salinity conditions. This work underscores the need for continued research to develop robust protocols for microbiome stewardship that enhance plant resilience and improve the success of future wetland restoration efforts. 

Abstract While wetlands represent a small fraction (~5%–10%) of the world's land surface, it is estimated that one‐third of wetlands have been lost due to human activities. Wetland habitat loss decreases ecosystem benefits, including improved water quality and climate change mitigation. These microbially mediated functions are dependent on redox conditions, which are altered by soil hydrology and the presence of plants. We tested the overarching hypothesis that while microbial community composition would be resistant to change due to long‐term hydrologic history, key functions like greenhouse gas production would remain plastic and responsive to short‐term environmental shifts. Using a mesocosm design, we manipulated the duration of hydrologic conditions (i.e., stable dry, stable flooding, and alternating wet/dry) and the presence of plants to induce soil redox changes in wetland soils. We measured soil redox status, used targeted amplicon and shotgun metagenomic sequencing to characterize microbial communities, and measured greenhouse gas production to assess microbial function. The 8‐week hydrologic treatment shifted community composition but did not override the stronger effects of long‐term hydrologic history. Methane and carbon dioxide fluxes were altered by short‐term hydrologic treatment, with methane production favored in the wet treatment and carbon dioxide production favored in the dry treatment. Plant presence versus absence manipulation had little impact on soil microbiome composition or soil greenhouse gas production. The results highlight the resistance of microbial community structure shaped by historical hydrologic regimes, and emphasize that hydrologic conditions exert a stronger influence than plant presence on microbial composition and function. Predicting the outcomes of wetland disturbance and restoration requires an enhanced understanding of community stability and functional plasticity. Our results suggest that wetland hydrologic restoration can establish a stable microbial community that is resistant to environmental shifts, but microbial functions such as greenhouse gas emissions remain responsive to hydrologic disturbances, including flooding and drought. 

Agriculture is a major contributor to nutrient pollution that drives eutrophication in aquatic ecosystems. This study integrates hydrological modeling with farmer behavioral analysis to assess the effectiveness of two agricultural conservation practices—cover crops and reduced nitrogen fertilizer application—in reducing nitrate loss from fields in the Tar-Pamlico River Basin of North Carolina. Survey responses from 279 farmers revealed widespread reluctance to adopt conservation practices, particularly strict fertilizer reductions. A hydrological model showed that applying each practice to 25 percent of agricultural land could substantially reduce nitrate export, with cover crops showing greater effectiveness than reduced fertilizer use. However, an integrated socio-hydrological model, which incorporated behavioral responses from farmers, predicted much smaller reductions in nitrate loss due to limited voluntary adoption. Specifically, nitrate reductions were overestimated by a factor of 8 for cover crops and by a factor of 25 for reduced fertilizer application when behavioral responses were excluded. This result highlights a critical limitation of traditional modeling approaches and underscores the importance of integrating human decision-making into environmental policy analysis. By linking policy incentives with both biophysical and social responses, this study offers a more realistic framework for designing cost-effective and impactful agricultural conservation strategies.