Seasonal Abundance of Groud-Occurring Macroarthropods in Forest and Canopy Gaps in the Southern Appalachians
Arthropods compose a large proportion of biological diversity and play important ecological roles as decomposers, pollinators, predators, prey, and nutrient cyclers. We sampled ground-occurring macroarthropods in intact gaps created by wind disturbance, in salvage-logged gaps, and in closed canopy mature forest (controls) during June 1998-May 1999 using drift fences with pitfall traps. Basal area of live trees, shade, and leaf litter coverage and depth were highest in controls and lowest in salvaged gaps. Coarse woody debris (CWD) cover was greater in intact gaps than in salvaged gaps or controls, but decay was more advanced and CWD had less bark in controls than gaps. We captured 2,390 grams (dry biomass) of > 28,000 macroarthropods in 21 orders and 66 identified families. Among orders, Coleoptera (36.4%) Hymenoptera (12.2 S), Orthoptera (11.7%) Araneae (7.1%), Julida (5.9%), Spirobolida (5.7%), and Scolopendromorpha (5.5%) were numerically dominant, whereas Coleoptera (44.0%), Spirobolida (19.9'%), Orthoptera (12.8%), Julida (6.8%), and Scolopendromorpha (5.0%) composed the majority of dry biomass. Total macroarthropod abundance and biomass were greater in forested controls than in intact or salvage-logged gaps, and was highest in summer, followed by fall, then spring, and lowest in winter. Differences among treatments were attributable to a higher abundance of Carabidae, Julida, Scolopendromorpha, Spirobolidae, and Araneae in forested controls than in gaps. Sclerosomatidae and Gryllidae were more abundant in salvaged gaps than in intact gaps or controls. Overall, mid-sized macroarthropods were more abundant than small (< 5 mm) or large (2 30 mm) macroarthropods, but those > 15.0 mm were more abundant in the controls. Small macroarthropods were most abundant in fall and winter. but those 2 5.0 mm were most abundant in summer and fall. Important questions that remain include whether reductions in macroarthropod numbers and biomass at the levels observed are likely to adversely impact vertebrate predators, and at which scales do impacts become a conservation issue.