Carbon and Energy Flow Dynamics in a Coastal Salt Marsh

This dissertation is based on measurements from a flux tower system utilizing eddy covariance methodology and other micrometeorological sensors during the period from May 2007 to December 2007 at the eastern shore of Virginia, USA over an intertidal salt marsh. Leaf level physiology measurements were undertaken to relate leaf-level exchange processes to ecosystem level. The particular physiology of Spartina alterniflora with a decreased phospho-enol pyruvate (PEP) carboxylase activity and low light saturation capacity and its implications on ecosystem level exchange processes are identified. Spartina alterniflora dominated intertidal salt marshes are moderate sinks for carbon fixing about 8-10 µmol m-2 s-2 of carbon dioxide during the active
growth stage, but become source of carbon dioxide during the inactive or winter months. Tidal
activity has a major role in modulating the partitioning of available energy and net ecosystem
exchange. The decreased assimilation rates observed under submerged conditions can be interpreted as a possible response of inter-tidal salt marshes to sea level rise as the hydro-period over a marsh increases. Land-sea breeze systems operating in intertidal coastal zones can advect moisture from the ocean surface and ecosystem level flux measurements should be interpreted by considering the advective processes in the interpretation of available energy partitioning. A biophysical model incorporating the C 4 photosynthetic pathway and incorporating the theories of turbulent transport relating source strength to concentration profile have been developed as a tool for accessing ecosystem response to climate forcings.

Note: Abstract extracted from PDF file via OCR