Japanese beetle, Popillia Japonica Newman, larvae alter aggregate dynamics in infested soil

Macrofauna can support or alter the biophysical state and function of soil. Many soil-dwelling invertebrates can affect soil stability by facilitating or hindering the soil aggregation process, changing the availability of plant and soil organic matter (SOM) for aggregate incorporation, and shifting the predominant mechanisms by which carbon and nitrogen are incorporated into soil aggregates. The current study examines soils affected by soil-dwelling larvae of the invasive Japanese beetle Popillia Japonica Newman (JB) in a Northern Indiana silt-clay-loam. We hypothesize that larval root-herbivory will inhibit the natural mechanisms of root input-driven, large soil aggregate formation, and consequently impede formation of intra-aggregates. JB may promote a different pathway for the creation of large soil aggregates by mixing digested root tissue and mineral soil in the gut, but with the absence of large intra-aggregate decaying root fragments. Present findings show a proportional increase of larger soil size fractions (2.0 – 8.0 mm) in the rhizosphere of infested soil after 1½ life-cycles of the beetle, but a decrease in the smaller soil size fractions (53 µm – 1 mm), and a faster incorporation of fresh organic carbon overall. These results may indicate a destabilization of soil structure over time in the stratum of highest JB larval activity, which in turn has the potential to expose a greater portion of soil carbon and nitrogen to mineralization processes and loss.