Occurrence of Carpenter Ants in Ozark Forests in Relation to Prescribed Fire and Stand Variables Robin M. Verble and Fred M. Stephen Fire is a natural abiotic disturbance agent that is important in determining the vegetation patterns observed in many hardwood forests. Although natural fire was suppressed through much of the 20th century, in the late 20th century, fire was reintroduced into many ecosystems in the form of prescribed burning. The effects of fire on insect populations are not well understood. The objective of this study was to assess the effects of prescribed fire, tree species, and tree size on black carpenter ant abundance and distribution. The effects of prescribed fire, tree species group, and tree dbh on black carpenter occurrence were studied using a presence–absence baited test on 3,556 trees in the oak– hickory forests of the Ozark Mountains of Arkansas. Trees were distributed over unburned areas and areas burned in the dormant seasons of 2005, 2006, and 2007. Black carpenter ants occurred most frequently at baits on large red oaks and least frequently at baits on small hickories, suggesting that they preferentially forage on certain tree species and sizes. Occurrence of black carpenter ants varied by fire treatment. Habitat alterations are likely to be a cause of ant occurrence patterns in oak– hickory forests, but additional studies are necessary to understand the mechanism behind this trend. Keywords: Camponotus, red oak borer, fire–insect interactions, oak– hickory forest, disturbance F ire is an ecosystem disturbance process, resulting naturally from lightning strikes and other ignition sources during peri- ods of high fuel flammability. Several southeastern US eco- systems including longleaf pine savannas, oak– hickory savannas, shortleaf pine forests, and tall grass prairie evolved in conjunction with fire (Brockway and Lewis 1997, Batek et al. 1999). Of all the disturbance factors that influenced the development of hardwood forests, fire was perhaps the most important; fires also play a domi- nant role in sustaining the oak– hickory ecosystems of the Ozark Highlands (VanLear 2004). Pre–twentieth century fires were light-to-moderate intensity sur- face fires. Increased time between fires and fuel accumulation since fire suppression policies were enacted in the early 20th century have dramatically increased the hazard for intensive destructive wildfires in many stands (Guyette and Spetich 2003, Dey et al. 2004, Van- Lear 2004). Fire exclusion has also caused considerable shifts in the composition and dynamics of the Ozark oak-hickory forests, includ- ing higher densities of trees per acre (Foti 2004), invasion of oak stands by shade-tolerant species, decreased oak regeneration (Van- Lear 2004), and increased competition from fire-intolerant species (Brose et al. 1999). Prescribed fire is a management tool that clears dead and dying plant material; reduces understory vegetation (Ahlgren and Ahlgren 1960), tree density (Foti 2004), and the invasion of exotic plants; increases species diversity (Brockway and Lewis 1997); aids in the control of plant diseases; and restores fire-dependent ecosystems (Habeck and Mutch 1973, McRae 1994). Since 1990, prescribed fire management of oak-hickory forests has become increasingly prevalent. In 2006, 21,853 ha of oak-hickory forests in the Ozark National Forest (ONF) of Arkansas were treated with prescribed fire. This is a significant increase from 2004, when 12,140 ha were managed with prescribed fire, although both are still a small fraction of the 485,622 ha that compose the ONF (Andre et al. 2007). Habitat disturbances influence the composition and structure of ant communities (Andrew et al. 2000). The effects of prescribed fire on ants (Hymenoptera: Formicidae) have been studied in ponderosa pine forests (Stephens and Wagner 2006), tropical cloud forests (Schonberg et al. 2004), desert grasslands (Zimmer and Parmenter 1998), and agroecosystems (Castano-Meneses and Palacios-Vargas 2003). The effects of both wildland and prescribed fire on ant spe- cies composition and abundance vary by ecosystem and fire inten- sity and interval. Thinning (Schonberg et al. 2004) and deforesta- tion (Sorvari and Hakkarainen 2007) have been shown to cause changes in ant abundance and diversity. Ant communities are influ- enced by habitat type (Yanoviak and Kaspari 2000), although evi- dence suggests tree species composition is not an important variable affecting most ant communities, because they nest in fallen logs and leaf litter (Hill et al. 2008). However, black carpenter ants (Cam- ponotus pennsylvanicus DeGeer) nest in and forage on standing trees, so tree species may be important in predicting their occurrence (Hansen and Klotz 2005). Carpenter ants (Camponotus Mayr) have been implicated as predators of several forest pest insects, including western spruce budworm (Choristoneura occidentalis Freeman; Youngs and Camp- bell 1984), jackpine budworm (Choristoneura pinus Freeman; Allen et al. 1970), Swaine jackpine sawfly (Neodiprion swainei Midd.; Received June 25, 2008; accepted January 8, 2009. Robin M. Verble (rmverble@ualr.edu) and Fred M. Stephen (fstephen@uark.edu), Department of Entomology, Agriculture 319, University of Arkansas, Fayetteville, Arkansas 72701. The authors thank T.J. Kring and L.C. Thompson for suggestions and reviews. They also thank T. CarlLee, L.D. Galligan, and M. McCall for their assistance in field studies. This project was funded in part by the Arkansas Agricultural Experiment Station and grants from the US Forest service, Southern Research Station and US Forest Service, Forest Health Protection, Spatial Technology Development Program and Forest Health Monitoring Programs. This article uses metric units; the applicable conversion factors are: centimeters (cm): 1 cm = 0.039 in; milliliter (ml): 1 ml = 0.27 fluid drams; hectares (ha): 1 ha = 2.47 ac. Copyright © 2009 by the Society of American Foresters. 42 SOUTH. J. APPL.FOR. 33(1) 2009 ABSTRACT Downloaded from https://academic.oup.com/sjaf/article/33/1/42/4774759 by guest on 08 December 2021