Plant Pollinator Networks in Fire-Maintained Sandhills

  • Technician Scott Gilb organizing pollinator specimens from the direct observations.

  • Specimens collected from June through October are ready to ship to be ID-ed.

  • A butterfly pollinating Carphephorus corymbosus.

  • Observers walking pollinator transects.

  • A bee pollinating Liatris tenuifolius.

Before humans ever dipped a paddle into Gulf waters or walked under sabal palms, lightning-ignited wildfires occurred naturally in Florida for millennia, fostering a diversity of plant and animal species that thrive in the open, grassy landscapes maintained by frequent fire. Beginning in the 1930’s, the widespread practice of fire suppression caused the decline of many of Florida’s fire-dependent ecosystems, leading to a loss of both plant and animal diversity. Many of the plant species that contribute to Florida’s unusually high biodiversity are found in the understories of fire-dependent longleaf pine savannas, which in turn support hundreds of vertebrate wildlife species. Pollinating insects perform a critical ecosystem function in these unique landscapes, helping to support plant populations and the animals that depend on them. The main purpose of this project by FWRI’s Upland Habitat Research and Monitoring team is to fill major data gaps on pollinator species diversity, plant/pollinator network structure, and pollinator habitat conservation in fire-maintained longleaf pine sandhills.

Flowering plants and their pollinators form interacting networks, which are heavily influenced by prescribed fire and vegetation structure. Through management actions, like altering the frequency and seasonality of prescribed burns or applying hardwood removal treatments, conservation managers can have a substantial amount of control over these flowering plant/pollinator networks, most notably by increasing the abundance and diversity of flowering plants throughout the year. This project will provide data for researchers and managers on the co-occurrence of plant and pollinator species in longleaf pine sandhills of peninsular Florida, in relation to management-influenced habitat variables such as fire frequency, fire seasonality, and forest stand structure.

The study sites for this project are located at nine different fire-managed sandhill preserves in north-central Florida: Ft. White Wildlife Environmental Area, Bell Ridge Wildlife Environmental Area, River Rise Preserve State Park, Jennings State Forest, Black Creek Ravines Conservation Area, Ordway-Swisher Biological Preserve, two separate tracts of Withlacoochee State Forest, and Chassahowitzka Wildlife Management Area. These study sites have been chosen carefully in order to account for a variety of environmental variables that may influence the effects of prescribed fire and ecological restoration in different environments. These data will be useful for management in promoting plant/pollinator networks and species diversity through carefully managed prescribed burns.

Within each preserve, 2 to 3 sampling plots, each 1 hectare in size, (1 hectare = 100m x 100m) were established, mapped, and marked.  LiDAR elevation data and aerial photography were used to quantify the forest stand structure within each 1ha plot, as well as the characteristics of the surrounding landscape. Plant species were assessed in a grid of twenty-five 5m x 5m sampling subplots laid out across the hectare. Five aerial pollinator trapping arrays consisting of vane and bowl traps were deployed for 24 hours once a month in each 1 hectare plot from March through October. Plant/pollinator interactions were recorded monthly using a timed meander transect method, during which the observer captures every pollinating insect encountered and records the associated flower species. Flower abundance counts and soil moisture readings were collected monthly within each 1 hectare plot. All collected insects were pinned and are currently being identified by experts and research technicians. Data analysis will include a variety of multivariate methods, including multi-species habitat occupancy modeling that will improve habitat quantification for difficult-to-detect species. The data collection is complete, and follow-up laboratory work is nearing completion. Preliminary data analysis is underway, and the bulk of the analysis will be completed during 2021.

Two University of Florida professors and their students have played key roles in this project: Dr. Benjamin Baiser, quantitative ecologist with the Department of Wildlife Ecology and Conservation, is leading the network analysis and habitat modeling with his students; and Dr. Eben Broadbent, spatial ecologist with the School of Forest Resources, is leading the collection and analysis of LiDAR and aerial imagery data for quantifying vegetation structure within and around the research plots. Dr. Josh Campbell, entomologist at Auburn University, has served as the primary insect identification expert for the project. All of the agencies that hosted research plots for this study have also been invaluable partners, including the Florida Forest Service, the Florida Department of Environmental Protection, the St. John’s River Water Management District, the Ordway-Swisher Biological Preserve, and the Canaan Ranch. The project was led by Dr. Johanna Freeman of FWRI’s Ecosystem Assessment and Restoration section (Upland Habitat Research and Monitoring subsection), with thanks to FWC’s Division of Habitat and Species Conservation/Wildlife Diversity Conservation. This project was funded by grants from the U.S. Fish and Wildlife Service (State Wildlife Grants Program), and the Fish and Wildlife Foundation of Florida (Conserve Wildlife Tag Program).

The research plots have been permanently marked, and long-term experimental fire regime treatments will be applied by the managing agencies. Additionally, these researchers have applied for funding to expand this methodology to other regions and habitats in Florida. The biologists and researchers hope their results will provide actionable insights into plant/pollinator network interactions that can be used by land managers to tailor prescribed fire regimes and/or other management interventions to promote pollinator conservation.