Mixed Session – 3:40

Drainage ditch wetlands cover approximately 3% of Buck Island Ranch and contribute to a food web that includes wading birds, hawks and owls. In the present study, we quantified the abundance of macrofauna (crayfish, shrimp, fish and amphibians) that are likely to contribute to this food web in a set of ditches that are the subject of an ongoing study of wading bird use. Macrofauna were sampled at randomly determined locations along the wading bird transect with a 0.25 m² throw trap. The animals collected were identified, enumerated, and released. In August, 51 samples were collected that averaged 36.4 cm in water depth, and 68% of these contained floating vegetation. Only 4 samples did not contain macrofauna, and the rest contained from 1 to 6 taxa. Total mean density was 38 individuals/m², and all taxa exhibited highly contagious distributions ( 2 test for agreement with a Poisson series). The Everglades crayfish (Procambarus alleni) averaged 2/m², while the grass shrimp (Palaemonetes paludosa) averaged 1.7/m². Of the 11 species of fish collected, the mosquitofish (Gambusia) and the least killifish (Heterandria formosa) had the highest densities at 13 and 11 fish/m², respectively. This study shows that macrofauna are abundant but patchily distributed in ditches.

Mixed Session – 3:20

Studies concerning the effect of habitat and landscape characteristics on community composition are relevant to the conservation of animal populations in complex and dynamic landscapes. Assemblages of species occupying habitat patches are considered nested when species making up relatively species-poor biotas are subsets of the species found in species-rich biotas. Nestedness may be particularly useful for conservation management because it identifies those species most at risk from human activities. Nestedness has been reported for many taxa in fragmented habitats, and occurs when extinction and colonization dynamics within a habitat patch are largely determined by habitat and landscape characteristics (e.g., wetland size, and isolation). My objectives are to determine 1) if fish and amphibian assemblages exhibit a nested subset structure and 2) which habitat and landscape characteristics most influence nestedness patterns in these assemblages in isolated wetlands. I will sample fish and amphibian larvae by dipnetting, throw trapping and funnel trapping in 24 isolated wetlands at MacArthur Agro-ecology Research Center (MAERC), central Florida, from October 1998 to September 2000. This study represents the first investigation of the effect of habitat and landscape characteristics on nestedness in isolated wetland fish and amphibian assemblages.

Avian Ecology Session – 10:20

Food supplementation experiments often are designed to examine relationships between food and the timing of breeding; however, few have measured the consequences of altering the timing of breeding. We studied Florida scrub-jays over 5 years at Archbold Biological Station where only natural food is available and in a suburban habitat where supplemental food is available year round. Supplemented jays bred significantly earlier and had less between-year variation in laying date of first-clutches (median laying date varied by 4 days) than unsupplemented jays (median laying date varied by 27 days). In both habitats, nesting success was similar and declined at the same rate over the course of the breeding season. However, contrary to the predictions of this latter relationship, nest success in suburban habitats was low and brood reduction was high when the jays nested early relative to those in the natural habitat. In natural habitats, scrub-jays may use environmental cues to determine when breeding should begin so that the presence of dependent young occurs when their required insect food reaches a peak. In suburban habitats, scrub-jays may use supplemental food as a breeding cue thereby decoupling their decision to breed from natural variations in insect food.

Avian Ecology Session – 11:20

Red-cockaded woodpeckers (RCWs), a cooperative breeder, excavate roosting and nesting cavities in living pines. RCWs rarely colonize unoccupied habitat without existing cavity trees, thus the availability of unoccupied cavities and breeder mortality may limit new breeding opportunities. At Avon Park Air Force Range, where we have studied RCWs since 1993, RCW territories contained many suitable cavity trees (mean = 17 ± 7.2), more than required by each territorial group. Annual survival rates of breeding and non-breeding males were high (85% and 88%) relative to other well-studied RCW populations. Thus, many more HY males survive to become yearlings than there exist breeding opportunities for them each year. This suggests that breeding limitation may be relatively severe at APAFR. Consistent with predictions of habitat-saturation models for the evolution of cooperative breeding, fewer HY males breed at APAFR, many reside as helpers at their natal territory for 3 or more years, and age-at-first breeding is delayed. Of 4 known-age birds that have become breeders, the mean age at first breeding was 3.5 years and 3 of 4 (75%) inherited their natal territory. However, the mean foray distance of HY males searching for breeding vacancies was greater than in many other populations.

MAERC Session – 1:00

In an effort to restore the sensitive ecosystems of south Florida, large reductions in phosphorus discharges are required from major land uses in the region. Beef cattle pastures cover large land areas resulting in large collective contributions of phosphorus. An interdisciplinary team has launched a project to develop sustainable environmentally-sensitive cattle ranch management practices for the region. The project is using a 16-plot, 1040-acre pasture array system to evaluate the effects of cattle stocking rate on: (1) runoff water quality, (2) biological agro-ecosystem indicators including animal performance, vegetation/forage quality, soil nutrient dynamics, nematode biodiversity, and avian utilization, and (3) ranch sustainability as predicted by economic models that integrate cow-calf performance and other financial considerations. The goal of this project is to provide information regarding the interrelationships and interactions of the overall agro-ecosystem and its sustainability, including tools to evaluate the performance of the overall system. To test the effects of grazing intensity on water quality and nutrient assimilation, this study imposes four cattle stocking rates on both an improved pasture site and a native range site. Data collected will be analyzed using standard statistical tools to test the hypothesis that stocking rate has no effect on runoff water quality, nutrient assimilation, or biological agro-ecosystem indicators. This approach constitutes a holistic analysis of ranch agro-ecosystems as affected by cattle stocking density.

MAERC Session – 2:00

An extensive infrastructure of hydrologic and water quality measurement systems have been installed at the MacArthur Agro-ecology Research Center. The purpose of these measurements is to determine the effect of cattle grazing density on off-site nutrient runoff loads from pasture lands. The data systems at MAERC contain unique design elements to address the difficulties of water budget measurements on south Florida flatwoods landscapes. The current network of measurement systems includes 16 ditch monitoring stations and 3 weather stations supporting the cattle stocking rate experiment fully described on the web page at www.imok.ufl.edu/buck. Trapezoidal flumes represent the primary flow measurement system at MAERC. The flumes located at the downstream end of each plot and collect of surface water runoff from each experimental pasture plot. The plots are hydrologically isolated from each other by the construction of ditches and berms. Data loggers/controllers at each flume compute and record flow data and activate automatic water samples based upon instantaneous flow conditions. Water samples are analyzed for total and soluble P, nitrate plus nitrite, ammonia and TKN. Flow data from the flumes are combined with nutrient concentration data to determine loading rates for total phosphorus, soluble phosphorus, nitrate, ammonia and total nitrogen.

Mixed Session – 4:20

Yellow bowls filled with water have recently appeared in aggregations around the Archbold Biological Station. Analysis of associated bronco tracks suggests a bug lab derivation. These bowls selectively trap certain groups of small insects. For unknown reasons, among the most common victims are wasps of the Proctotrupoidea, especially the family Scelionidae. The scelionid wasps develop as egg parasitoids of arthropods, one wasp per egg; they are usually extremely small. Our list of these egg parasitoids at the Station is growing amazingly fast, thanks to Dr. Lubomir Masner (Canadian National Collection), who is identifying the specimens from the yellow bowls. Since Dr. Masner has sampled proctotrupoids from throughout eastern North America, it is already possible to begin to put our yellow bowl fauna into perspective. This produces new mysteries about large-scale geographic trends in insects. For example, in the Northeast, spider egg sacs are commonly attacked by an abundant and diverse group of ichneumonid wasps, the genus Gelis. At the Station, Gelis is represented by two rare species, but egg parasitoids of the genus Idris (Scelionidae) are remarkably abundant and diverse. Idris occurs in the Northeast, but at a much-reduced level. It is fun and instructive to speculate on the reasons for these distributions, which make up only one of a number of emerging patterns. Then, of course, a functional mystery appears. Under what developmental regime can these larval speculations grow and metamorphose to become adult scientific theories?

Mixed Session – 4:00

The Archbold Biological Station currently offers a variety of activities to help inform students, visitors and the local community on the Florida Scrub Ecosystem. The Education Office offers scheduled talks and tours on request to the general public, environmental education activities to all public and private school grade levels, and teacher workshops. It oversees the Nature Trail, Butterfly Garden and visitor information kiosk, conducts four summer camps, designs displays, and runs the Archbold Volunteer Program. In 1998, the Education Office received a grant from the Advisory Council on Environmental Education (through the Florida Game and Fresh Water Fish Commission) to fund a project entitled Discovering Florida Scrub. Devoted exclusively to Florida Scrub, the project will include production of Florida Scrub curriculum and development of a teacher training workshop. With this grant project, we hope to provide elementary teachers and informal educators the knowledge, skills and confidence needed to explore scrub with their students.

MAERC Session – 2:40

The Buck Island Ranch's 1996 financial results had been roughly estimated using a Standardized Performance Analysis system developed at Texas A&M University by Dr. James McGrann and others. The same data were analyzed with a financial cow-calf simulator (Patent applied for) initially developed by John Earman. Those analyses led to improvements in Ranch accounting information and to some changes in management practices on the Ranch. Similar analyses of 1997 data will be completed using the same evaluative instruments. Tentative conclusions will be drawn about the efficacy of ranch data collection systems. Also the capability of SPA and the simulator to support decisions by ranch management will be compared. Two years' data will give some insight into emerging ranch performance trends.

MAERC Session – 1:40

During the summer season, bahiagrass production is at its peak and beef cattle cannot efficiently utilize the available forage. Excess bahiagrass is stockpiled for winter grazing. Unfortunately, the stockpiled bahiagrass is low in forage quality, unpalatable to cattle, and molasses supplement must be fed to encourage utilization of the bahiagrass. Sheep and goats are often utilized for biological brush and weed control in pastures. We hypothesize sheep will graze and reduce the amount of stockpiled bahiagrass and weeds in the pasture and thus improve forage quality of the bahiagrass and cattle performance. Over a six-month period (November-April), 500 rambouillet yearling wethers will rotationally graze (2-4 inch stubble) stockpilied bahiagrass pastures. Three weeks after the sheep leave a grazed paddock the cattle will follow. Vegetation measurements will include species composition, bahiagrass production, and forage quality. Weight and body condition score of the sheep and cattle will be recorded every 28 days. Fecal samples will be collected at the time animals are weighed and internal parasite numbers will be determine in both sheep and cattle.

Plant Ecology Session – 9:40

Spatial variation in Florida scrub vegetation appears to be associated with small variations in topography. It is assumed that topography influences soil moisture availability, but this has never been shown directly, as critical differences may appear only briefly during certain periods. We are sampling at Archbold Biological Station in order to detect differences in soil moisture patterns in 3 types of scrub communities (Rosemary Scrub, Scrubby Flatwoods, Hickory Scrub), and assess the effects of a recent prescribed burn (vs unburned) and aboveground vegetation gaps (vs shrub cover) on soil moisture. The sampling design has 3 replicates. We record soil moisture data one day per week, at 3 depths (10, 50 and 90 cm) in PVC tubes inserted into the soil. A probe instantaneously and directly measures soil moisture, using Frequency Domain Reflectrometry (Sentry 200, Troxler Ltd.). Sampling began October 1 1998 and will continue at least to the end of May 1999. Concurrently, pre-dawn water potential will also be measured on 2 common shrubs and 2 endangered herbs. Preliminary results suggest that SF soils have the highest soil moisture at 90 cm, and that burning and gaps have little influence. However, we expect more differences to appear during prolonged dry periods.

MAERC Session – 1:20

Long-term sustainability of a cattle ranch ecosystem is dependent on many variables including the ability of soils to retain and recycle nutrients such as phosphorus. Retention of phosphorus from animal feces and urine by soils is important to the fertility status of the soils, pasture productivity, and water quality in the watershed. A replicated, field-scale beef cattle grazing experiment to examine the influence of grazing density (no grazing, and low, normal, and high stocking rates) and differences in land use (improved pasture vs. native wet prairie pasture) has been established at the MacArthur Agro-ecology Research Center at Buck Island Ranch. The theme of the project is to manage the ranch for the multiple objectives of cattle production, water quality protection, and wildlife habitat enhancement. Soils on the Ranch are primarily Spodosols, Entisols, and Histosols. The surface horizons of these soils typically have a low retention capacity for phosphorus. Additionally, the pastures are artificially drained by an intensive network of shallow ditches. These conditions enhance the lateral movement of water and nutrients into the drainage network and ultimately into nearby water bodies. Preliminary data relating water-soluble and acid-extractable soil phosphorus concentrations to soil phosphorus retention capacity will be discussed.

Plant Ecology Session – 8:40

Prescribed burning is an important tool for maintaining native habitats. Lack of burning leads to high fuel loads that can cause intense, hard to control fires. Certain vegetation types, such as scrubby flatwoods and yellow-sand scrub will only burn under windy, dry conditions that make controlling a "controlled burn" a difficult task. Firebreaks at Archbold are 3-10m wide. Untreated, these firebreaks are not wide enough to control fires in units that have high fuel loads and/or scrub vegetation. Some guides for prescribed fire management suggest that firebreaks be at least two times as wide as the expected flame length. Flame lengths on scrub fires are often 4-6m or more, depending on fuel and weather conditions. Firebreaks around these units would have to be 12m or wider to abide by the above conditions. Also, while scrub fires burn intensely as head fires, they often burn only patchily as backfires. Other lighting techniques must be employed to create a safe blackline. In order to get around this, Archbold and other agencies have begun to use mowing to reduce vegetation height at the fireline. Mowed vegetation drys out and is easier to burn with backfires. Width of mowing depends on vegetation height, conditions in adjacent units, unit size, and prescribed wind direction. Mowing can also be used to temporarily divide units without causing soil disturbance.

Avian Ecology Session – 10:40

Wetland loss and hydrological changes throughout Florida have been implicated in declines of wading birds, many of them listed species. Most of Florida’s wading bird estimates come from the Everglades and, more recently the Okeechobee region. In contrast few data are available for the extensive agricultural areas of south central Florida, in particular the large private cattle ranches. Understanding wading bird utilization of these ranches may help explain spatial and temporal patterning of these species regionally. We present data from a long-term study of wading birds at the MacArthur Agro-ecology Research Center, a 4,170-ha cattle ranch, managed at commercial production levels. The goals of this project are to determine: (1) relative abundance of various species; (2) seasonal and annual variation in numbers; and (3) variation in spatial patterns of use among species. Ground-surveys were conducted, at first quarterly, then monthly, along a 21.7 km ditch transect. Observations were made of all wading birds within 100 m on each side of the ditch, in a variety of habitats including wet prairies, marshes, ponds, and improved and native pastures. Since 1989 we have observed more than 11,000 wading birds, of 14 species, largely white ibis, great egrets, little blue herons, wood storks, great blue herons and snowy egrets (listed in order of declining abundance). We examine how the spatial and temporal patterning in wading bird numbers in these agricultural areas are related to local and regional patterns and discusses the implications of these findings for management of wading birds.

Plant Ecology Session – 9:00

Fires often rejuvenate populations of fire-adapted species, including those of Florida scrub. Temporal and spatial heterogeneity in fire regimes may also affect scrub populations. For example, temporal variation in fire return intervals is predicted to reduce extinction probabilities in Hypericum cumulicola. Either temporal uniformity or extreme temporal variation can threaten species, but this vulnerability depends on life history. In plants, seed banks can decrease this vulnerability, but seed banks of Dicerandra frutescens become depleted with fire suppression. The demography of Florida scrub-jays has been used to define fire return intervals for scrubby flatwoods; likewise, Florida rosemary reproduction and Eryngium cuneifolium extinctions bracket intervals for rosemary scrub. Seasonal variations in burning have relatively minor effects on scrub organisms. Large, uniform fires may create local extinction risks, while patchy fires or fire mosaics can provide refugia, for example in allowing continuous nesting of the Florida scrub-jay. Spatially patchy burns could be beneficial to species with poor dispersal like D. frutescens, but this seems difficult to demonstrate due to the many differences between burns. Variation in patchiness and fire intensity is partly within the control of prescribed burners. The Archbold Biological Station fire management plan embraces temporal and spatial variation in the fire regime.

MAERC Session – 1:40

The University of Florida/Institute of Food and Agricultural Sciences, Archbold Biological Station, South Florida Water Management District and the Florida Cattlemen’s Association are cooperating on a multidisciplinary project to develop sustainable cattle production systems. Information is lacking regarding the animal-forage-watershed interrelationship in ranching systems where animal behavior and performance have been examined. Part of the experiment will examine the effect of stocking rate on water, soil, forage quality and animal performance. Results of this research will provide information on the relationship among cow-calf management practices on forage characteristics, animal behavior and performance, and soil and water quality. Results will be used for developing a beef ranch decision support system and hydrological modeling.

Welcome – 8:20

Many field stations in North America, such as Archbold, belong to the Organization of Biological Field Stations (OBFS). We will demonstrate how these OBFS stations collectively represent an established network of sites able to detect, understand, and interpret ecological change at a regional/national level. Stations are located in 40/50 states, with the greatest number in California (21) and New York (13). Only Alabama, Arkansas, Connecticut, Delaware, Hawaii, Maryland, New Hampshire, North Dakota, Rhode Island, and Vermont have no current members. An overlay analysis shows that OBFS stations represent data collection points in a significant proportion of the ecoregions of the lower 48 states, providing coverage of representative biomes. We compare this coverage with that of other monitoring networks. OBFS field stations also serve as foci to provide advice to solve regional conservation issues. Our survey of 42 OBFS member sites showed they work on a range of issues, including listed species (60%), invasive species (60%), water quality (62%) and planning for protected areas (57%). Stations work collaboratively with state and federal agencies particularly the U.S. Forest Service (31%) and state game/conservation agencies (40%). Over 36% of OBFS stations were active with local government. Many stations (38%) also interact with The Nature Conservancy, indicating a strong working relationship between OBFS and this non-profit conservation organization.

Plant Ecology Session – 9:20

Florida ziziphus (Ziziphus celata Judd & Hall [Rhamnaceae]) is a xeromorphic shrub endemic to the Lake Wales Ridge and currently known from only five sites in Polk and Highlands Counties. Allozyme electrophoresis suggests that a single multi-locus genotype occurs at each of four sites. We conducted a series of breeding system experiments to test the self-compatibility of one population and its compatibility with several outcross genotypes. We also tested the self-compatibility of off-site genotypes conserved in a captive population at Bok Tower Gardens (BTG). We found that our study population was self-incompatible. Between-genotype crosses within the off-site population at BTG (consisting of seven genotypes) yielded twelve mature fruit. Non-treated open-pollinations yielded a substantial crop. Conservation of this species requires the establishment of several breeding populations. Further investigation of the breeding system of Florida ziziphus is necessary in order achieve this goal. This work was funded in part by the U.S. Fish and Wildlife Service and Bok Tower Gardens.

Avian Ecology Session – 11:00

A year-long survey of macro-biota was conducted at the Buck Island Ranch Agro-ecology experimental pastures, to serve as baseline data to evaluate changes over time with variable cattle stocking rates. Vegetation, birds, and mammals were sampled in four seasons during 1995-6 in summer (improved, upland) and winter (native, wetland) grazing areas. Forty-six and 54 species of birds were identified in summer and winter pastures, respectively. Of the 16 nesting birds species, three species were restricted to summer pastures and six species to winter pastures. White-tailed deer were most often identified in the winter pastures, while feral pigs were found in both areas, but at four times greater densities in the summer pastures. Twenty-three species of grasses were identified, with bahiagrass the dominant species in both grazing areas. Forage production and forage use in the summer pastures were highest during the summer, but from fall to winter, forage production was less than forage loss. In contrast, forage production in winter pastures (though lower overall than that in summer pastures) was equal to, or greater, than forage use during the winter period. Differences were also found among the eight experimental pastures within each seasonal grazing type, including differences in plant species composition within both grazing areas, differences in plant standing crop, and densities of breeding bird territories in summer grazing areas. These differences among the experimental pastures seem related to amount of standing water, and vegetation cover.

Avian Ecology Session – 11:40

Opposing hypotheses ("pair-formation" and "dominance") have been proposed to account for sexual asymmetries in proportions of natal prebreeders remaining home with various combinations of stepparents and parents. At ages 1 yr and 2 yr equal proportions of females remained home with stepfathers and fathers and equal proportions of males remained home with stepmothers and mothers (all contra pair-formation). At ages 1 yr and 2 yr proportionally fewer females remained home with stepmothers than mothers, and at age 1 yr proportionally fewer males remained home with stepfathers (all pro dominance), but equal proportions of age 2 yr males remained home with stepfathers and fathers. The critical test is the proportions that remained with two stepparents versus both parents, as pair-formation predicts proportionally more and dominance proportionally fewer with stepparents than parents. At age 1 yr fewer prebreeders of each sex remained with stepparents (contra pair-formation, pro dominance). At age 2 yr the proportions of females remaining with stepparents versus parents was unclear, but equal numbers of males remained with the two categories of breeders. We established that stepparents were more aggressive than parents toward prebreeders of like sex, and that no natal prebreeder has ever paired with a stepparent (pro dominance). Age 2 yr males, which were exceptions to the dominance hypothesis, may remain in their natal territories despite stepfather aggression in order to obtain a breeding territory through budding or inheritance.