Colorado mountains
From Long-Term Data to Understanding: Toward a Predictive Ecology
2015 LTER ASM Estes Park, CO - August 30 - September 2, 2015

28 Years of Landsat 5 TM and external forcing data for analysis of Spartina biomass on the Central Georgia coast

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John O'Donnell
John Schalles

The focus of this Georgia Coastal Ecosystems LTER project was to develop a standardized workflow for batch processing ~ 3 decades of Landsat TM images in order to produce vegetation indices and above ground plant biomass maps and size class phenology and inter-annual variation for Georgia coastal wetlands. Our work focused on Spartina alterniflora, the dominant halophyte in Southeast Atlantic salt marshes. We also related seasonal and inter-annual Spartina biomass variations to coastal ecosystem drivers (river discharge, precipitation, time-integrated tidal stages, temperature, and drought index) at varying precedent time spans  (1, 3, 6, and 9 month integrations).  We developed a robust Spartina alterniflora biomass algorithm that exhibits accurate separation among height classes and captures annual phenology. Landsat 5 TM image data captured spatial and temporal trends in Spartina alterniflora, and provided a useful monitoring tool –  if effective screening was done for clouds, tidal inundation, and haze effects. We conclude that substrate salinization in times of drought or reduced flooding is a major stressor, with strongest effects on late summer to fall biomass. One major, but preliminary finding is that Spartina biomass decreased over the 28 yrs of our study. This project provides the Georgia Coastal Ecosystems LTER with a workflow scheme to continue monitoring Spartina biomass using the new Landsat 8 OLI sensor and the new ESA Sentinel 2A and 2B sensors.

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