The aim of this study is to understand how topographic variation alters the effects of forest management on local invertebrate biodiversity. Rapid reproductive rates and high sensitivities to environmental factors and limited dispersal make invertebrates useful for studying short-term effects on dynamic landscapes. Prior studies show that invertebrate diversity and composition shift in response to forest succession following clearcutting. For instance, clearcutting practices in mesic valley microhabitats affect arthropods and leaf litter decomposition to a lesser extent than clearcutting practices in hilltop xeric microhabitats. This study was conducted within 4-ha experimental forests that were clear-cut in 2008 in Morgan-Monroe and Yellowwood State Forests, Indiana. Study sites consisted of 16 paired 50-m transects, with controls (unmanaged forest) and a corresponding clear-cut transect. At each site, one pair of transects was located on a hilltop (xeric) and one within a valley (mesic). Additionally, half the transects were located on a southwest facing slope, and half on a northeast facing slope. Canopy tree composition was recorded along each transect, and leaf litter was collected for invertebrate extraction and soil moisture measurements at 3 locations (0-m, 25-m, and 50-m). All invertebrates were identified to order, with ants and carabid beetles identified to species.
Results/Conclusions
We predicted that drier xeric soils would have lower diversity and abundance of invertebrates compared to mesic soils. We also predicted that the open canopy following clearcutting will negatively affect forest-dwelling invertebrates. Consistent with predictions, overall invertebrate abundance was 30% higher in unmanaged stands than in clearcut areas (p<0.001) and in locations with greater soil moisture, such as mesic NE-facing valleys (p<0.001). Similarly, carabid beetle abundance was 95% greater in unmanaged areas compared to clearcut stands (p<0.001), as well as more mesic locations with greater soil moisture (p<0.001). In contrast, ant abundance was 78% greater in clearcut stands than in unmanaged forest stands (p<0.001), due primarily to the increase in disturbance-tolerant species found in clearcuts and xeric locations (p<0.001). The variation in responses of ants and carabid beetles to forest management and topographic position compared to that of overall invertebrate abundance, suggests the need for caution in applying the responses of these commonly used indicator taxa to the overall invertebrate community.