Ash mortality caused by emerald ash borer alters the forest floor environment and invertebrate community

Emerald ash borer (EAB), Agrilus planipennis, an invasive wood-boring beetle from Asia, has killed millions of ash trees (Fraxinus spp.) in North America.  Ash mortality caused by EAB has resulted in wide-scale simultaneous formation of canopy gaps and increased ash coarse woody debris (CWD) in invaded forests.  Because soil invertebrates are sensitive to environmental change, CWD is thought to stabilize environmental conditions on the forest floor (e.g. temperature, moisture) and buffer changes to the forest floor habitat caused by increased light.  A manipulative experiment was conducted in forest stands at the NASA Plum Brook Station in N Ohio to determine the effects of light gaps, CWD, and their interaction on the forest floor invertebrate community.  A full factorial experiment was designed with two treatments: presence/absence of light gaps and CWD.  Abundance and diversity of invertebrates was assessed with pitfall traps.  Soil temperature and moisture were measured adjacent to pitfall traps, and canopy gap size was assessed with a densiometer.  Light measurements indicated successful implementation of the light availability treatment resulting in the formation of large (20-26%) and small (7%) canopy gaps.  Soil temperature increased in gaps and soil moisture followed a similar trend.  There was an interacting effect of light gap and CWD on invertebrate diversity.  Invertebrate abundance and species richness decreased in the presence of light gaps.  Soil invertebrates are important in forest ecosystems because they mediate the process of decomposition and nutrient cycling, thereby linking above and below ground food webs.