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Grantee Research Project Results

Grantee Research Project Results

Pasture Management, the Red Imported Fire Ant (Solenopsis invicta), and Dung Beetle Mediated Ecosystem Services

EPA Grant Number: FP917504
Title: Pasture Management, the Red Imported Fire Ant (Solenopsis invicta), and Dung Beetle Mediated Ecosystem Services
Investigators: Steele, Christen H
Institution: University of Central Florida
EPA Project Officer: Cobbs-Green, Gladys M.
Project Period: August 20, 2012 through August 19, 2014
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2012)
Research Category: Academic Fellowships , Fellowship - Ecology

Description:

Objective:

Grazing animals in Florida deposit more than 20 million metric tons of dung per year, making dung a significant non-point source of pollution. Degradation of this dung occurs naturally, primarily due to Coleopterans (beetles) in the families Scarabaeidae and Geotrupidae (hereafter dung beetles). Dung that is not degraded may be leached into water bodies and provides an incubation site for the pests and parasites of both humans and livestock. Thus, the optimization of the ecosystem services provided by dung beetles is a priority for not only the protection of terrestrial and aquatic biota, but also the cattle industry. This project will utilize seminatural and intensively managed pastures to determine how management driven differences in habitat alter dung beetle assemblages. This study also will evaluate experimentally how pasture type and the presence or absence of the non-native red imported fire ant influence the ecosystem services of dung degradation and parasite suppression.

Approach:

This research will be conducted at MAERC (part of Archbold Biological Station), a 4,170-ha commercial cattle ranch in central Florida. Dung baited pitfall traps will be used to determine the diversity, abundance and biomass of beetles within semi-native and intensively managed pastures. The influence of pasture type and fire ants on ecosystem services will be assessed using 20 treatment grids (10 in each pasture type). Each grid will consist of two 30 ×30 m plots; one as a fire ant exclusion and the other as a fire ant inclusion. Experimental dung pats placed within the treatment grid also will exclude or include dung beetles using a dome-shaped wire frame wrapped in mesh. Parasite abundance will be sampled by collecting vegetation surrounding the pat and extracting infective larvae using a modification of the methods of Whitehead and Hemming (1965 Ann Appl Biol 55: 25-38). Dung pats will be collected from the field after 40 days and oven dried to determine the rate of dung degradation.

Expected Results:

It is expected to find greater diversity of dung beetle species and functional groups in the semi-natural pastures on MAERC, as it is suspected that intensive management practices such as high fertilizer use and frequent mechanical disturbance will result in localized extinction of largebodied species. Preliminary sampling results conducted in spring of 2011, revealed a trend of increased species richness within semi-natural pastures. Higher beetle diversity is expected to increase dung degradation but may not increase parasite suppression. During preliminary sampling, fire ants foraged in high quantities within more than 70 percent of pats. Large numbers of fire ants within a pat are likely to increase pat aeration and desiccation. Although this will not improve dung degradation, it may lead to increased parasite mortality.

Potential to Further Environmental/Human Health Protection

A multitude of controlled experiments have shown that biodiversity has a significant influence over ecosystem function and services. These studies make clear that the preservation of diverse natural areas and semi-natural areas is paramount to the delivery of the ecosystem services on which humans rely. Agricultural systems, like natural systems, can sustain biodiversity and provide valuable ecosystem services, but this may depend on the methods used to manage these systems. Because this project will focus on the relationship between biodiversity and function within a working landscape, it provides the opportunity to examine the influence of diversity as it interacts directly with livestock and human health. This project will inform ranch managers on the importance of regulating natural systems on their ranches and may lead to modification of management practices to maintain beneficial ecosystem services.

Supplemental Keywords:

water quality, ecosystem services, nutrient recycling

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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