It’s all in the Roots – what’s under the dirt can be a measure of marsh health
Marsh plants, such as Spartina alterniflora, in Folly River of Georgia from February 2023 have extensive root systems that allow them to populate and create large marsh systems. The recent study proves that estimating the root production is an essential measurement to determine the health of coastal ecosystems. Credit Kyle Runion.
Coastal salt marshes can combat sea-level rise by generating extensive root structures which help build the surface elevation. However, measuring these root structures to assess marsh health is muddy work. In a new study published in Ecosphere, researchers developed a new tool to evaluate marsh health by estimating root production, with no hip-boots needed.
The study, which took place across coastal Georgia, found relationships between root production and a variety of environmental conditions which can be described by satellite data, tide records, climate stations, and elevation measurements. By quantifying these relationships with extensive field measurements, they calibrated a prediction model that can be applied in novel settings to assess marsh health.
“I call the tool my ‘root x-ray glasses,’ because with it, we are essentially peeking through the flooded, muddy ground to survey root growth” said lead author Kyle Runion, a PhD. Student at the University of Texas Marine Institute in Port Aransas, Texas. “Because our tool applies real-time data from satellites and climate stations, we can use it to scale-up and make predictions of plant growth and health across space and time. This information can help coastal managers restore at-risk coastal wetland areas.”
Researchers found that root production varied with many environmental conditions, representing a complex response to changing environments. Runion explained “assessing root production is tricky, because it doesn’t always vary consistently across environmental gradients and there can be a lot of ‘noise’ in the data. That makes it difficult to apply simple relationships to assess marsh health. We found that it took a comprehensive approach to create a reliable prediction model.”
Consequentially, the relationship between leaf and root growth was inconsistent. This suggests that marsh health assessments that rely on aboveground metrics may miss key signals only revealed beneath the surface.
One strong relationship the researchers did find was declining root production at higher flooding rates. This implies vulnerability to marsh drowning with high rates of sea-level rise. The tool developed in the study, called the Belowground Ecosystem Resiliency Model, is freely available for use online for coastal managers and researchers to identify priority marsh locations for conservation and restoration. Prompt intervention may be necessary to avoid marsh drowning in areas which are experiencing accelerated sea-level rise.
Kyle Runion is joined by coauthors Deepak Mishra and Merryl Alber at the University of Georgia, Mark Lever at the University of Texas Marine Science Institute, and Jessica O’Connell at Colorado State University. The research was supported by the NOAA Margaret A. Davidson Graduate Research Fellowship, NASA FINESST grant (80NSSC23K0300), and the NSF Georgia Coastal Ecosystems Long Term Ecological Research Project.
