Ash mortality caused by emerald ash borer impacts forest floor invertebrate communities

Emerald ash borer (EAB; Agrilus planipennis) is an invasive wood-boring beetle native to Asia. Since its introduction into North America, EAB has killed untold millions of ash trees, resulting in widespread simultaneous formation of canopy gaps in forests. Gap formation may alter environmental conditions on the forest floor, potentially impacting populations of ground-dwelling invertebrates. However, as dead trees fall, accumulation of coarse woody debris (CWD) may buffer environmental changes on the forest floor induced by increased light. The objective was to quantify the effects of gap formation and accumulation of CWD caused by EAB-induced ash mortality on forest floor invertebrate community diversity and composition. A two-year, manipulative experiment was conducted in forests at NASA Plum Brook Research Station in Ohio to determine the effects of light gaps, CWD, and their interaction on forest floor invertebrates. Canopy gaps altered the invertebrate community by decreasing family and guild richness in 2011. However, the effect of gaps varied between years, and was marginal in 2012. Invertebrate community composition shifted as important members of predator and detritivore guilds were more prevalent under closed canopy. Although gaps increased soil temperature and soil moisture overall, the difference in environmental conditions between gaps and closed canopy habitat was greater in 2011 than 2012. Invertebrate community response was dependent on the degree of environmental differences between habitats. CWD had no effect on forest floor invertebrates. EAB indirectly impacted forest floor invertebrates through changes in environmental conditions on the forest floor caused by ash mortality.