COMMUNITY AND ECOSYSTEM ECOLOGY Salvage Logging, Edge Effects, and Carabid Beetles: Connections to Conservation and Sustainable Forest Management 1 2 2 3 IAIN D. PHILLIPS, TYLER P. COBB, JOHN R. SPENCE, AND R. MARK BRIGHAM Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Environ. Entomol. 35(4): 950Ð957 (2006) ABSTRACT We used pitfall traps to study the effects of Þre and salvage logging on distribution of carabid beetles over a forest disturbance gradient ranging from salvaged (naturally burned and subsequently harvested) to unsalvaged (naturally burned and left standing). SigniÞcantly more carabids were caught in the salvaged forest and the overall catch decreased steadily through the edge and into the unsalvaged forest. We also noted a strong negative correlation between carabid abun- dance and percent vegetation cover. Beetle diversity as measured through rarefaction was signiÞcantly greater at the edge relative to both the unsalvaged and salvaged forest. This stand level study suggests that the amount of edge habitat created by salvage logging has signiÞcant implications for recovery of epigaeic beetle assemblages in burned forests by inßating the abundance of “open habitat” species in the initial communities. Carabid beetle responses to salvage logging can differ from responses to harvesting in unburned boreal forest suggesting that management of postÞre forests requires special consideration. KEY WORDS carabid beetles, salvage logging, boreal forest, edge effects Boreal forests are structured by cycles of wildÞre and emela¨ 1997, Helio¨la¨ et al. 2001). Thus, it seems that postÞre regeneration (Larsen 1970, Bonan and Shu- invertebrates could be vulnerable to salvage logging. gart 1989, Johnson et al. 1998), a disturbance regimen In this study we compared the diversity, species that is being altered by human activities. For example, composition, and abundance of carabids among three postÞre salvage harvesting recovers low-grade timber post Þre habitats: (1) burned forest, (2) burned and from the landscape in an attempt to minimize eco- then salvaged forest, and (3) the edge separating nomic losses caused by Þre. It is a relatively new them. In addition, we studied associations between disturbance, and the impact of salvage logging on vegetation and carabid catch rates. Carabid assem- wildlife in boreal habitats is poorly known (Harmon blages are appropriate for disturbance studies because 2001, Nappi et al. 2004). Furthermore, salvaged areas of their high abundance in boreal forests, their sensi- fragment burned forest into patches that have higher tivity to habitat change (Niemela¨ 1990, Niemela¨ et al. amounts of distinct edge than in natural postÞre sit- 1990, 1992, 1993, Abildsnes and Tømmerås 2000), and uations in which the only edges occur along windfalls the efÞciency with which they can be sampled (Hunter 1993) and water bodies (Harper and Mac- (Spence and Niemela¨ 1994). The overall goal of this donald 2001). study was to determine if decisions about salvage log- Effects of fragmentation and direct loss of burned ging might have conservation implications for carabid habitat resulting from salvage logging on the distribu- beetles and, perhaps, for other epigaeic organisms. tion, composition, and abundance of wildlife have not been studied in detail, except for birds (Haggard and Materials and Methods Gaines 2001, Kotliar et al. 2002, Morissette et al. 2002). Work in Finland, however, provides examples of ar- Study Area. The study was conducted Ϸ200 km thropod species declines as well as local extinctions northwest of Edmonton, Alberta, Canada, within the being caused by such habitat changes in boreal forests boundaries of the Chisholm Þre, a severe, large-scale (Rassi et al. 1992, Siitonen and Martikainen 1994, Ni- wildÞre (Ϸ120,000 ha) that burned during the spring of 2001. The speciÞc sampling location was a burned 1 Correspondning author: Department of Biological Sciences, Uni- white spruce [Picea glauca (Moench) Voss.] stand versity of Alberta, Edmonton, Alberta T6C 2E9, Canada (e-mail: (Ϸ35 ha) Ϸ7 km from the town of Chisholm, AB [email protected]). (54Њ55Ј N, 114Њ10Ј W). The forest companies involved 2 Department of Renewable Resources, University of Alberta, Ed- in salvage logging in this area agreed to leave a portion monton, Alberta T6G 2E3, Canada. Ϸ 3 Biology Department, University of Regina, Regina, Saskatchewan of this stand ( 6 ha) for use in experiments, and this S4S 0A2, Canada. provided the unsalvaged habitat for this study. 0046-225X/06/0950Ð0957$04.00/0 ᭧ 2006 Entomological Society of America August 2006 PHILLIPS ET AL.: SALVAGE LOGGING AND EDGE EFFECTS 951 Sampling Design. Epigaeic beetles were captured Species richness estimates were obtained by rar- using pitfall traps (Spence and Niemela¨ 1994) con- efaction using internet-based software (Brzustowski structed by burying a 1-liter white plastic container 2003). Rarefaction corrects for sampling effort vari- (11.2 cm in diameter) even with the surface of the ability by modeling expected species richness as a ground. A 0.5-liter inner plastic cup was placed tightly function of subsamples of the original catch, thereby in this outer sleeve and Þlled with Ϸ150 ml of silicate- allowing comparisons between samples of similar size free ethylene glycol. Trapped specimens were re- (Hurlbert 1971, Buddle et al. 2005). However, we moved periodically, and traps were reÞlled with fresh calculated the Shannon-Wiener diversity index for ethylene glycol. All traps were covered with a 15 by each trap distance from the edge and used ANOVA to 15-cm plywood lid elevated several centimeters above test for a signiÞcant effect of habitat on diversity. the trap to reduce disturbance to trap catches and To test for relationships between the carabid abun- ßooding by rain. Although data from pitfall traps is dance and environmental variables studied (percent biased in some respects, they remain the most widely vegetation cover, percent bare ground cover, and per- used technique for sampling epigaeic arthropod as- cent litter), we calculated Pearson correlation coef- semblages. We used pitfall catches, as recommended, Þcients (Zar 1999). However, because diversity did to compare the relative abundances of a species not meet the assumptions of parametric tests, Spear- among similar habitats (Niemela¨ et al. 1993). manÕs rank correlation was used to study possible Pitfall traps were deployed on three replicate correlations between environmental variables and transects 25 m apart and oriented perpendicular to the carabid diversity (Zar 1999). boundary (edge) between burned salvaged forest and To test for species-level responses, a multivariate standing burned forest. Unfortunately, replicate un- analysis of variance (MANOVA) (followed by salvaged stands were unavailable for study, and thus TukeyÕs post hoc tests where appropriate) was per- formed on the Þve most abundant carabid species we were restricted to replication of transects at three Ϸ well-separated points (Ͼ25 m) across a single edge. ( 87% of the total sample). Community-level re- Previous work has shown that traps placed 25 m apart sponses were examined using nonmetric multidimen- in boreal mixedwood forest sample statistically inde- sional scaling (NMS). This analysis was performed pendent populations (Digweed et al. 1995). We using the software package PC-Ord (McCune and Medford 1999) and S rensen (Bray-Curtis) as the placed traps at intervals of 0, 10, 20, 30, and 40 m from ø distance measure. To further examine carabid com- the edge and into each of the two respective habitat munity responses to the three habitats, we used indi- types (Spence et al. 1996). Thus, each transect con- cator species analysis (Dufrene and Legendre 1997) to sisted of nine traps over a total transect length of 80 m. ˆ identify if species occurred predominately enough to In our analysis, we regarded the traps at 0 m and those be considered signiÞcant indicators of a given habitat. located at 10 m on either side as edge habitat, transi- For all statistical tests, we used a rejection coefÞcient tional between the salvaged and unsalvaged areas. of 0.05. Beetles were collected continuously between 26 June and 22 August 2002. Traps were serviced at ϳ2-wk intervals. No traps were lost over the course of Results the experiment. After sorting, all carabids were sub- Species Occurrence Across the Edge. We captured sequently identiÞed to species according to Lindroth a total of 2,494 carabid beetles representing 35 species (1963Ð1969), and identiÞcations were compared with during the study. Total carabid abundance was highest reference specimens at the University of Regina, Uni- in the salvaged habitat, followed by the edge and versity of Alberta, and the Royal Saskatchewan Mu- lowest in the unsalvaged stand (Fig. 1). Pterostichus seum. Voucher specimens for all species are deposited adstrictus Eschscholtz was the most abundant species in the E. H. Strickland Entomological Museum (Uni- (860 individuals comprising 34% of the total sample; versity of Alberta) in Edmonton, Canada. Table 1), and Sericoda quadripunctata (DeGeer) was Vegetation Analysis. We estimated percent ground the second most abundant (680 individuals comprising cover by vegetation, bare ground, and litter in a grid 29% of the total sample; Table 1). (1.0 by 1.0 m) around each pitfall trap. All plant spe- Carabid Community Assemblages. Salvage logging cies were identiÞed according to Johnson et al. (1995). in this stand resulted