Differential Growth Dynamics of Common Salt Marsh Species Spartina alterniflora and Juncus roemerianus Under Varied Sediment Amendments
Abstract
Introduction
Many coastal wetlands are at high risk of degradation or loss due to sea‐level rise. Restoration techniques for maintaining coastal marshes are paramount, with thin‐layer placement (TLP) emerging as one feasible solution. Despite TLP's utilization, additional research is needed on species‐ and sediment‐specific responses.
Objectives
Our research combines greenhouse and field experimentation to test species and sediment composition responses aimed at maximizing vegetation while maintaining increased elevation.
Methods
The greenhouse experiment used two common marsh plants, Spartina alterniflora and Juncus roemarianus. Five centimeters of sediment (mud, sand, and sand/mud mix) was added, and subsequent sediment and vegetation metrics were monitored. The field experiment focused on S. alterniflora and examined multiple sediments (mud and sand/mud mix) in coastal Virginia, United States.
Results
In the greenhouse, Spartina and Juncus had similar responses to sediment types with no differences to the control, but sand producing greater aboveground biomass compared to mud. Spartina outperformed Juncus overall and Juncus root biomass was negatively impacted by sand compared to the control. Compaction occurred across all sediments, with greater loss in the sand compared to the mud and control. In the field, mud and mix treatments had lower aboveground metrics compared to the control groups and saw no differences in elevation even after amendments.
Conclusions
These results showcase the importance of initial marsh plant response in a species‐ and sediment‐specific manner. Further, they highlight differences between research settings, sediment additions, and metric specific outcomes.
Implications for Practice
Controlled greenhouse experiments paired with field experiments provide a valuable window into species‐specific and short‐term response of coastal marsh response to thin‐layer placement practice. By examining multiple species, a more comprehensive view of responses is possible for targeted approaches and benchmarks. While long‐term success is an ultimate goal, short‐term impacts can have immediate and lasting implications on multiple ecosystem properties and processes. Understanding these short‐term fine‐scale responses can resolve recovery trajectories early on and provide critical information on implementation, which may allow enough time and planning to provide mitigation in subsequent seasons. Ideally, identifying potentially negative impacts of restoration activities in the short term to improve long‐term outcomes.