The purpose of this effort is to determine the unique aspects of the 1999/2000 growing season that caused the spatial and temporal pattern of marsh dieback along coastal Louisiana during summer 2000. No single approach by itself can address the causes. What is needed is an integrated approach that uses a combination of controlled greenhouse and field studies, compilation and analysis of historical data sets of climatic and hydrologic data, modeling, and assessment of patterns of marsh recovery in the field.

Task II.1
Conduct experimental studies of Spartina alterniflora and associated salt marsh plants to determine their tolerance to various environmental stressors and their interactions. Possible stressors may include, but are not limited to, salinity, pH, moisture, metals, and pathogens. Selection of stressors will be coordinated with investigator of Task II.2.

TASK II.2
Conduct experimental studies to determine how different hyrologic drivers and different saline marsh soil types will generate plant stressors evaluated in Task II.1. Studies may also include plant-soil interactions. Possible hydrologic drivers may include, but are not limited to, elevation in relation to tidal inundation, tidal exchange, surface and ground water recharge, location relative to adjacent surface water bodies, precipitation, evapotranspiration, and soil permeability.

TASK II.3
Conduct field studies to identify site-specific hydrologic drivers and soil characteristics at the salt marsh study sites already established in 2000. Possible hydrologic drivers may include, but are not limited to, elevation in relation to tidal inundation, surface and ground water recharge, location relative to adjacent surface water bodies, precipitation, evapotranspiration, and soil permeability. Possible soil characteristics may include, but are not limited to, soil chemistry, and mineralogy.

TASK II.4
In a subset of the salt marsh study sites already established in 2000 and noted in II.3, conduct monthly in-depth vegetative assessments and analyze selected soil physiochemistry variables. Possible biological variables may include, but are not limited to, live and dead stem densities, growth and survival of tagged shoots, expansion or decline in area of surviving patches, stem heights, stem/leaf stress categories, and production of flowers/seeds. Environmental variables, measured in adjacent waterways and at the surface and various depths in the marsh root zone, may include, but are not limited to, Eh, pH, salinity, sulfides, and nutrients.

TASK II.5
Compile and analyze historical data sets of external environmental drivers potentially contributing to the 2000 marsh dieback. Drivers may include, but are not limited to, climate, riverine discharge, coastal water levels, and salinities.

TASK II.6
Construct a coupled hydrological/ecological model(s) that uses the environmental stressors and hydrologic and climatic drivers identified in Tasks II.1 through II.4 to hindcast marsh soil conditions potentially contributing to marsh dieback and to forecast the potential for future brownmarsh events as a function of environmental conditions.