Assessing Insect Communities and Plant-Pollinator Networks in Fire-Maintained Sandhills

by Johanna Freeman

The arthropod fauna of xeric longleaf pine savannas has been conservatively estimated at 4,000 to 5,000 species.  This diversity virtually guarantees that insects play numerous and complex roles in the functioning of longleaf pine sandhills, but little is known about sandhill insect communities and how they are affected by land management activities.  In particular, fire effects on plant-pollinator interactions are poorly documented, and at present there are few management recommendations regarding pollinators in fire-maintained sandhills. 

The Upland Habitat research group is working on a project designed to collect baseline data on sandhill insect communities, as well as identifying areas in which fire management can influence insect species diversity and plant-pollinator networks.  In collaboration with University of Florida community ecologist Dr. Benjamin Baiser and his students, we are sampling 24 1-hectare research plots at 9 fire-maintained sandhill preserves once a month from March to October 2019.  The study sites have been chosen carefully in order to provide adequate replication of a variety of environmental variables (soil moisture, soil texture, and elevation) and standardize others (time-since-fire), which will enable us to sort out anthropogenic sources of variation from natural environmental gradients.  We are also collaborating with Dr. Eben Broadbent of the University of Florida spatial ecology lab, who will be using a combination of LiDAR and high-resolution aerial imagery to quantify landscape-scale structural and spatial variables surrounding the research plots. 

Butterflies pollinating Cirsium horridulum. Photo by Cherice Smithers.

Every month, the research team deploys five insect-trapping arrays in each plot for 24 hours.  The arrays consist of vane traps, pitfall traps, and bowl traps, each of which targets different types of insects.  Plant-pollinator interactions are also observed in each plot once a month.  Each 1ha research plot is divided into 4 quadrants, within which an observer walks a serpentine transect covering the entire quadrant over the course of 30 minutes, for a total of 2 hours sampling time per plot per month.  Every time the observer encounters an insect interacting with a flower, he/she captures the insect for identification and notes the plant species upon which it was encountered.  All flowering plant species within the 1ha plot are identified during the monthly visit, and flower abundance counts are conducted.  Back at the lab, research technicians have their work cut out for them sorting and pinning hundreds of insect specimens, which are being identified by entomologist Dr. Josh Campbell of Auburn University. 

The Upland Habitat group is grateful for all the support we have received in implementing this challenging field project.  It has been very much a team effort, requiring the input of several specialists and entailing a heavy schedule of monthly field work.  The project has been made possible by funding from the State Wildlife Grants program and the Fish and Wildlife Foundation of Florida, and the cooperation of the Florida Forest Service, Florida Park Service, St. John’s River Water Management District, Florida Fish & Wildlife Conservation Commission, and private landowner Nolan Galloway, Jr.  We look forward to analyzing the data and learning much, much more about this important component of sandhill ecosystems!