Swallow Cliff Restoration Effects project

Introduction

This multidisciplinary Field Museum-based project involved study of numerous groups of animals, plants, and fungi in an area targeted for and then undergoing restoration work in an overgrown oak woodland (Swallow Cliff Woods) in southwestern Cook County, Illinois. A similar nearby area not targeted for restoration work (Cap Sauers Holdings) was used as a control. Working in cooperation with the Forest Preserve District of Cook County (landowner), the Illinois Nature Preserves Commission (overseer of the control area) and The Nature Conservancy (collaborating with FPDCC on land management), we sought to determine the effects of management activities (in this case, prescribed burns to clear the shrub layer) on diverse members of the ecological community, most of which had never been assessed in such a way. The groups studied were: rove, carrion, and ground beetles, spiders, millipedes, slugs and landsnails, mushrooms, amphibians and reptiles, birds, mosses, and flowering plants.

Sampling

Sampling was done for arthropods (beetles, spiders, and millipedes from the list above) in 1996-2000 using standardized protocols of trapping (flight intercept, pitfall, and carrion-baited pitfall) and litter-sampling (2-3 kg sifted samples extracted with Berlese funnels) at two sites in each area. Sampling visits were made every two weeks, with 11-15 sampling periods each in 1996-1999 and 4 in 2000. The collections from 1996-1999 provide baseline data, and the 1999-2000 collections provide post-treatment data, following prescribed burns in late March or early April of each year. Samples were sorted and identified at the Field Museum, and all voucher specimens are deposited there and available for further study. Because of the need for much additional taxonomic work on Staphylinidae, the species of many genera, especially most in the huge subfamily Aleocharinae, cannot be identified reliably. Identifying the local Silphidae, however, is no problem.

Checking mini-flight intercept trap ©The Field Museum, GN88392_31c	Picking up and resetting a carrion-baited pitfall trap ©The Field Museum, GN88393_15c

Results

The lists available below summarize the 1996-2000 rove and carrion beetle results. The cumulative list shows all identifiable taxa collected, representing 6 species of Silphidae and at least 182 of Staphylinidae. The year-to-year comparison list includes only the collections made during an 8-week period corresponding to the 2000 sampling (22 June-21 August). It is further restricted to species that were collected at both sites before the burns and of which we collected at least 5 individuals in each area. This restricted set of taxa includes 37 species of rove beetles and 5 of carrion beetles; the sixth carrion beetle species, not collected pre-burn at Swallow Cliff during this part of the season, is also listed. Taking both families together, 16 species showed slight to very strong post-burn decreases in abundance at Swallow Cliff compared to Cap Sauers ("-" in the list). Twelve species showed slight or distinct increases ("+" in the list), and 15 showed either no pronounced change or generally erratic numbers.

The labels of "woodland specialist" (found only in woodland or savanna) vs. "habitat generalist" (found also in prairies) are preliminary assessments based mainly on recent collecting in Chicago Wilderness, because very little such information is available in the literature. Among generalist species, nearly equal numbers showed increases, decreases, and no change; among the woodland/savanna species, 8 decreased (2 strongly so), 2 increased, and 4 showed no or erratic change. The strongest decreases compared to the control site ("strong -" in the list) occurred in Ontholestes cingulatus and Platydracus violaceus, two large species of rove beetles that are strongly forest-associated, although the meaning of change in the latter is uncertain, because its numbers also dropped at the control site. Platydracus zonatus, a related forest species, showed a smaller decrease. It is puzzling that Nicrophorus pustulatus, believed to be forest-associated, was only collected at Swallow Cliff (at this time of year) following the burns; a few specimens were, however, collected there earlier in the season in 1997.

Acknowledgments

This project was made possible by grant support from the Conservation Foundation (for Chicago Wilderness) to the office of Environmental Conservation Programs (ECP) of The Field Museum. For the beetle part of the project, this funding supported essential technical assistance with fieldwork and identification and preparation of specimens. Valuable preliminary data on habitat preferences of local Staphylinidae and Silphidae were gathered in the course of the Illinois Rapid Assessment Program (IRAP) that was part of a contract between the Illinois Department of Natural Resources (1997-1999) and ECP. I initially made the scanned images of Silphidae as part of protocol development for UrbanWatch (a part of EcoWatch) under the same contract.

The Field Museum supported an intern in 1995 and 1996 who helped with data entry for the literature checklist, as well as supporting the high-school level "Biodiversity Explorers" program. These high-schoolers helped greatly with field work and initial sample sorting in 1999 and 2000, and in fact field work would not have been done at all in 2000 without their help. The project benefited throughout from help in the field by a succession of interns, volunteers, and students as well as museum staff.

Permission to collect as needed at Swallow Cliff Woods and Cap Sauers Holdings was provided by the Forest Preserve District of Cook County, the Illinois Nature Preserves Commission, and the Illinois Department of Natural Resources. Field work for IRAP was made possible by permission from those agencies and also Midewin National Tallgrass Prairie.