60-30 Relationship Between Vegetation and Belowground Biomass Across Nine Louisiana Coastal Basins

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

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Abstract:

Coastal marshes in Louisiana are critical carbon sinks that provide a range of ecosystem services, including shoreline protection and habitat. Marsh vegetation increases the strength of soils via belowground biomass (BGB). Quantifying how attributes of BGB – rooting depth, diameter, and density – vary informs our understanding how marshes form, survive, and degrade, as well as provide an indication of health and stability. However, how the vertical distribution of BGB varies across marsh types and vegetation species is not well understood. This study leverages data from the Louisiana Coastwide Reference Monitoring System (CRMS) to examine trends in vertical distribution of live BGB across nine coastal basins. BGB samples were collected at 144 sites in 8 cm increments to a depth of 24 cm and were examined across multiple vegetation community types (VCT) and marsh elevations. Linear regression and Kruskal-Wallis tests were used to assess BGB distribution of six dominant marsh species. Results show that BGB generally decreases with soil depth with highest values found near the surface (0 – 8 cm). Spartina alterniflora and Spartina patens displayed the highest BGB values, while intermediate and freshwater species showed lower values and varied distribution. BGB and species distribution varied by VCT and elevation with mid-elevation marshes (0.18–0.30 m NAVD88) supporting higher average biomass and higher species composition than lower elevations. These results suggest that salinity and elevation influence the productivity of BGB for marsh species in coastal Louisiana. This information is important for predicting marsh resilience and designing restoration strategies as sea level rises and subsidence continues to threatened coastal ecosystems.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8297

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