Archbold Biological Station, Biennial Report 1997-1998

Patrick Bohlen; photo by Mike McMillian

MacArthur Agro-ecology Research Center
at Buck Island Ranch

Project Directors: Hilary M. Swain, G. Thomas Bancroft (1997), Patrick J. Bohlen (1998)
Ranch Manager: L. O’Gene Lollis
Associate Research Biologist: G.Thomas Bancroft (1997)
Assistant Research Biologists: David H. Anderson, Patrick J. Bohlen (1998)
Post-Doctoral Fellows: Bruce D. Dugger, Catherine M. Dugger, Soon-Jin Hwang
Research Assistants: Gabriele M. Aborn, Carrie J. Bullock, Charles H. Brown, Louis A. Capazza, Lisa M. Collins, Tammy L. Hammer, Dan M. Ingall, Steven M. McGehee, Michael A. McMillian, Kimberle L. Niewolyn, Edwin C. Rawlinson, Karen L. Rogers, Lourdes M. Rojas
Interns: Matthew J. Baber, Wendy Jess
Research Partners:

Outside Collaborators: Kim J. Babbitt, University of New Hampshire; Bruce D. Dugger, Southern Illinois University; Joan L. Morrison, Colorado State University

[Biennial Contents | Research Projects 1997-1998 |
Biennial 95-96 |

Grazing lands in Florida, as elsewhere in the USA, are complex ecological systems involving large-scale manipulation of ecological patterns and processes and the widespread modification of the spatial structure of the landscape. Florida is one of the leading cattle producers in the U.S., second only to Kentucky in beef production east of the Mississippi River and tenth nationally. There are approximately 5.5 million acres of range-pastureland in Florida, roughly 4.8 million of which exist in native range and 1 million in improved pasture. In 1998, 1,050,000 beef cow-calf units were supported on grazing lands in Florida, most of it privately owned, and generally focused in a ten county region in southwest-central Florida. Although cattle ranching and citrus production are a major land-use in Florida, the cumulative magnitude of the ecological effects of grazing and citrus on nutrient dynamics and patterns of species diversity is still largely unknown.

     The MacArthur Agro-ecology Research Center (BIR) examines ecological patterns and processes within this region to understand changes in species and ecosystems that occur in response to human alterations. The interdisciplinary teams at BIR—encompassing ecologists, economists, range scientists, agricultural engineers, hydrologists, soil scientists, animal scientists, statisticians, and ranchers—have a variety of research aims including:

  • increasing knowledge of the ecological functioning of grazing lands,
  • assessing the consequences of alternative management practices, and
  • improving the capacity of decision makers and the general public to understand the ecological role of grazing lands.

     With the 10,300-acre Buck Island Ranch facility, on a 30-year lease to Archbold Biological Station from the John D. and Catherine T. MacArthur Foundation, BIR approaches research priorities at real-world agricultural scales, and with a day-to-day understanding of the economic realities of operating a cattle ranch. Using both observational and experimental approaches we address the very broad question: how are the ecological, economic, and physical factors involved in grazing lands related, and how do they change over time? During 1997–98 we collected integrated data on the relationships among these factors at the ranch to help determine effects on patterns of native biodiversity and fluxes of water and nutrients (Fig. 1). These factors can be integrated because they share the common spatial setting of the Ranch.

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[ Physical Factors | Ecological Factors | Economic Factors ]

    Physical Factors. The physical characteristics of the Ranch landscape provide the underlying infrastructure for ecological patterns and processes, and the economic performance of the Ranch. The predominant physical features of BIR are its climate, soils, hydrology, and lack of topography. Climatic conditions at the Ranch are currently being monitored by four weather stations that collect continuous data on temperature, rainfall, wind speed and direction, and solar radiation. Soils are poorly drained sands or very poorly drained organic soils with low to moderate fertility. Adequate moisture, high temperatures, and a long growing season allow for significant pasture productivity. Introduced pasture grasses, such as Bahia, occupy the better-drained areas of the Ranch (summer pastures). Native grasses and marsh species dominate the more poorly drained areas (winter pastures). These dominant landscape types are the basis of an extensive seasonal rotation in which the cattle are stocked more heavily on the Bahia pastures in the summer and are moved to the semi-native marshes in the winter.

    Minor variations in topography control variation in plant communities, with wetlands and marshes occupying poorly-drained, low-lying areas, and cabbage palm or live oak hammocks occupying higher, well-drained areas. Landscape depressions due to cavities in deep limestone formations have resulted in the development of over 500 isolated wetlands, which are critical resources for wildlife. In addition to natural wetlands, there is an extensive network of over 400 miles of drainage ditches to facilitate draining of surface water and ameliorate flooding during the rainy season.

Charles Brown, Research Assistant, connects a laptop computer to the data logger at one of 16 flumes and water samplers at the experimental pasture arrays.
A flume, including CR10 instrumentation and ISCO water quality sampler, at experimental pasture Winter-6; photo by Christine Ambrose

The main ditches drain directly into Harney Pond Canal, a major drainage way for the region, which connects us to the larger regional Kissimmee-Okeechobee-Everglades watershed, and ties us to the water quality concerns of the region. These concerns motivated us to establish, with our partners, a 490-hectare array of 16 experimental pastures (see maps [a], page 29) which are fully instrumented for monitoring water quality (see photos, this page). The experiment is currently examining the effects of cattle stocking density (0, 15, 20, 35 cow-calf pairs per experimental pasture) on water quality and other ecological patterns and processes.

    The cattle stocking treatments were begun in autumn 1998. The 16 experimental flumes and automatic water samplers continuously measure the amount and quality of water draining from the pastures during periods of flow. Water quality samples are sent to the Harbor Branch Oceanographic Institution Environmental Laboratory and analyzed for total nitrogen and phosphorous, ortho-phosphate, ammonium, and nitrate. The flow data and water quality data are transferred electronically to John Capece, who is directing the water quality research. Initial findings show that phosphorus loads in drainage waters are greater in summer than in winter pastures.

    Ecological Factors. The physical landscape mosaic leads to characteristic patterns in ecosystem patterns and processes that are the basis for variations in ecological productivity, nutrient storage, or flux in the landscape. There is a necessary emphasis on long-term studies to understand ecological factors in this agricultural landscape. Such data allow us to detect population trends, changes in natural community structure and resiliency, episodic and stochastic events, deterministic change (e.g. effects of climate change), and shifts in ecological processes.

Matthew Baber, graduate student, Florida International University, samples for tadpoles in an isolated wetland; photo by Christine Ambrose.

    Wetland conditions drive many of the ecological patterns seen on the Ranch. Mike McMillian, Hilary Swain, and Dave Anderson are examining seasonal and annual variation in the spatial patterning of wading bird use of ditches and adjacent habitats in relation to hydrological conditions, ditch maintenance, and aquatic prey availability. Monthly fluctuations in water depth, monitored manually with staff gages in some of the 56 miles of main ditches included in the 10-year-long wading bird survey, are a primary determinant of their function as wildlife habitat. Herpetological and aquatic community responses to land use pattern, hydrology, and agricultural practices in wetlands are being studied across the entire Ranch. Matt Baber, (see photo, this page) a doctoral student at Florida International University, is studying amphibian communities at BIR, and monitoring hydroperiods of selected isolated wetlands. Wendy Jess, research intern, conducted an initial survey of king rails throughout the Ranch in the El Niño winter of year of 1998 and found that the rails prefer semi-native wetlands with taller vegetation types. The important role of wetlands in maintaining several raptor populations has been revealed by Mike McMillian, Joan Morrison, and Tom Bancroft as they continued long-term studies of red-shouldered hawks, barred owls, and crested caracaras during 1997–98. They examined distribution, reproductive success, and prey availability in relation to the landscape mosaic of natural communities, and agricultural land use and practices. Other wildlife studies are Ranch-wide, such as the comprehensive point-count and other censuses of breeding and wintering birds started in 1997 by Bancroft and McMillian to examine trends in avian communities in relation to land use and agricultural practices. Volunteers from Highlands County Audubon Society are instrumental in completing annual Ranch-wide January surveys of the distribution of eastern phoebes (n=145-155), American kestrels (n=50-55), and great crested flycatchers (n=10-12) to assess population size and habitat use in ranchlands by these wintering birds.

    In 1998, we hired Patrick Bohlen as the new BIR Research Biologist to initiate a program of research on ecosystem processes, biomass/productivity measures, and nutrient fluxes in relation to grazing pressure, and other agricultural practices. One of his first projects is to examine the cycling of nitrogen and phosphorus in soil in relation to plant growth and cattle stocking density in the experimental pastures described above. He is working with Jeff Mullahey (IFAS), who is measuring aboveground productivity, to assess the importance of belowground productivity to overall production and nutrient storage in the pastures. He also plans to collaborate with Don Graetz (IFAS) on a project investigating ecosystem processes in the isolated wetlands on the Ranch.

    BIR lies in the watershed of Lake Okeechobee, a wetland system of national significance. As part of the wider BIR research program, ongoing research work by Dave Anderson and Bruce Dugger has focused on species distributions and aquatic community characterization in broader regional ecosystems including the Kissimmee River restoration project, Lake Okeechobee, and the greater Everglades region.

    Economic Factors. Research on the economic and production impacts of alternative management practices is needed to assess the balance between environmental protection and production goals. Fundamental to the overall research program is the further development of economic, and other databases to track agricultural practices such as stocking density, fertilization, burning and chopping, and renovation, for all the pastures and the citrus grove at Buck Island Ranch.

    Gene Lollis, Ranch Manager, and Lisa Collins further expanded the use of an economic analysis system, Standardized Performance Analysis (SPA), developed by the National Cattlemen's Association, to evaluate the production and financial performance of the beef cow/calf operation at Buck Island Ranch. Assistance has been provided by agricultural economists Fritz Roka, John Holt, and John Earman (IFAS). SPA provides a standardized tool that allows performance comparisons of an operation among years, producers, and regions. The SPA analysis is divided into two sections, production performance and financial and economic performance. The production analysis provides reproduction, production, grazing, and feed-performance measures over a "production year." The financial portion of SPA provides financial and economic measures over the fiscal year. SPA results are used to evaluate trends in production and financial performance of a beef cow/calf operation. Table 1 (see below) shows three of the SPA production measures. The average payweight price for calves (1a) reflects the low points in 1997 and 1998 in national trends for cattle prices. Pounds of calf weaned per exposed female (1b) provides an indicator of herd production. The calf crop (1c) is an important indicator of the herd's reproductive rate; conception was down statewide in 1997 because of difficult prior weather conditions in 1996, then conception rates rose again in 1998. The El Niño conditions of early 1998 had a negative financial impact on the Ranch resulting in lower citrus crop yields and a reduced calf crop for the 1999 cattle season. Strong links between prevailing weather conditions affect both ecological and economic responses on the Ranch. The production portion of SPA can be used to evaluate long-term trends on the pasture or herd scale. The financial analysis provides an appropriate measure for the entire beef cow/calf operation at the Ranch, but has limited capabilities for the individual pastures. However, specific financial measures, including pounds of weaned calf produced, and pounds of feed used, can be evaluated for individual pastures or herds (Table 2, see below). Financial record systems at the Ranch are being revised to improve input data and, therefore, improve the accuracy of the SPA results. Evaluating SPA and other financial results over time allows us to see where production and financial costs lie in relation to physical and ecological factors, and can be included in decision support systems to allow us to ask "what if" questions.

    Integration of Ecological, Economic, and Physical Factors Involved in Grazing Lands. While our long-term objective is to characterize the relationship between physical, ecological, and economic factors for the entire ranching landscape of the Okeechobee drainage basin, our research approach uses Buck Island Ranch to represent the range of conditions in this region. BIR’s work to date has started the long-term tracking of the ecological, agricultural, and economic resources, upon which this agro-ecosystem is built. As we build these spatially explicit databases we will start to test the framework and ask whether economic, physical, and ecological components share common spatial configurations, and whether each component responds to spatial and temporal changes in the other.


Table 1: SPA Production Measures (1997–1998)



a) Weighted Avg. Payweight Prices (All Weaned Calves)



b) Pounds Weaned per Exposed Female



c) Calf Crop Based on Exposed Females




Table 2: SPA Financial Measures (1997–1998)



a) Beginning Breeding Cow Inventory (Hd.)



b) Pretax Cost per Breeding Cow



c) Net Income per Breeding Cow



d) Economic Breakeven Cost/cwt of Weaned Calf Produced



* includes yearlings

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