MAERC at Buck Island Ranch
300 Buck Island Ranch Road Lake Placid, Florida 33852 USA
Phone: 863-699-0242 FAX: 863-699-2217 
Email: maerc@archbold-station.org

Synergistic Effects of Fire and Grazing on Wetland Ecosystems

Patrick J. Bohlen¹, David Jenkins², Pedro Quintana-Ascencio², John Fauth²

¹MacArthur Agro-ecology Research Center, ²University of Central Florida

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Project Summary

Understanding the impact of agricultural management on the structure and function of wetlands embedded in agricultural landscapes is critical for sustaining ecological functions and minimizing impacts of agriculture on water resources and aquatic communities.  These functions are especially important in regions, such as the rangelands of south Florida, where wetlands comprise a significant part of the agricultural landscape and thus are critical to interconnections between agricultural production, natural communities and downstream ecosystems.  The goal of this project is to understand the interactive impacts of major ecosystem drivers (i.e., pasture intensification, grazing and prescribed fire) on the ecosystem services provided by wetland ecosystems in subtropical grazing lands.

Wetlands provide essential ecological services including: water supply, high-quality forage, cooling and resting areas for cattle, nutrient storage and nutrient cycling functions, and vital habitat for wildlife.  Current rangeland management practices in South Florida use fertilizer to improve pasture quality, prescribed fire to prevent encroachment by shrubs and improve forage quality, and rotational grazing to maximize cattle production and seasonal forage utilization.  Much of the ranchland in this region has been converted to improved pasture with introduced forage species, but native or semi-native areas still comprise an important part of the landscape.  The rangeland and agronomic research in this area has focused on specific components of upland systems with much less emphasis on the embedded wetlands, which support high-quality forage production and provide a critical ecological link in the interconnected greater Okeechobee-Everglades ecosystem.  Sustaining natural functions within ranches will require a better understanding of how major management practices influence the structure and function of embedded wetlands on ranches.

We are examining how ecological services provided by wetlands on cattle ranches are affected by two widespread management practices (grazing and fire), in two major pasture types (improved and semi-native), with a replicated experiment on entire wetland ecosystems. We take a multidisciplinary approach to evaluate the impact of ranch management practices on wetland structure and dynamics and the consequences for production and conservation values of wetland systems.  Results from this project will be made available to ranch managers interested in enhancing wetlands within their properties, and will be incorporated into other education and extension efforts.  The project will also provide information for assessing the potential of ranch wetlands to contribute to important regional environmental goals that focus on improving water resources, enhancing wildlife habitat, and reducing invasive species in the Great Everglades.

This conceptual diagram illustrates the three major management drivers affecting wetlands on FL ranches, the main ecological characteristics of wetlands, and the agronomic and ecological wetland “products” valued by society.  The proposed project will use a replicated experiment on whole wetlands to examine the independent and interactive effects of the three major management drivers on wetland structure and function, and will assess the contribution of wetlands to production and conservation goals on cattle ranches.

Experimental Design

The experimental design consists of a 3-way factorial experiment that applies two treatments (grazing and fire management), plus account for pasture management effects by assigning experimental units (wetlands) to improved or semi-native pastures, which represent more intensive and less intensive pasture management types.  Grazing treatment consist of two levels: an open control (cattle have full access to wetlands), and permanent cattle exclosure.  Exclosures are made of barbed wire fence, and grazing intensity and timing in unfenced wetlands is according to customary ranch management—grazing  information on each pasture (duration, # of head) is maintained in a GIS-based pasture database at MAERC.  The fire treatment is the presence or absence of controlled burns within the wetlands, with burns occurring in Year 2 (2008) of the 3-year study, with the intent of continuing the fire treatment, pending continued funding for the project (fences and grazing treatment will be maintained for at least 10-15 years).  The management treatment (improved vs. semi-native pastures) is based on pasture land use categorization on MAERC GIS pasture coverages.