Effects of Disturbance and Fertility upon the Vegetation of a Louisiana Coastal Marsh: An Evaluation of Huston’s General Model of Diversity
P. Keddy

Project Overview

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The future of Louisiana’s coastal marshes is threatened by a multitude of factors including: relative sea level rise saltwater intrusion, altered hydrology (e.g. canal construction), exotic species, wave erosion, and the elimination of riverine inputs by artificial levees built along the Mississippi River. All of these factors combined result in some of the highest land loss rates in the world. Fire, herbivory,

nutrients, and sedimentation are major factors controlling marsh structure and composition; this study examines some of these factors.

There are two main objectives for the project:

1. to explore the effects of multiple disturbance and fertility regimes upon plant community structure, and

2. to set targets and provide guidelines for restoration.

The ranked disturbance treatments are control, prescribed fire (a common management tool), single herbicide, and double herbicide. Initial results show that nutria, the principal vertebrate herbivore of the marsh, may limit biomass production and increase species richness. Prescribed fire seems to promote heavy, localized herbivory in burned areas thereby, reducing the amount of organic matter incorporated in the soil. The sediment + fertilizer treatment, which simulates a proposed freshwater diversion, significantly increases biomass production with no reduction in species diversity.