LAND USE IMPLICATIONS OF MINERALOGICAL AND STRUCTURAL ALTERATIONS OF SOIL AGGREGATES UNDER ASIAN EARTHWORMS

This study quantifies mineralogical and structural alterations of silt loam aggregates along with nanoscale shell fabric and cocoon permeability properties of three species of invasive earthworms: Amynthas agrestis, Amynthas tokioensis, and Metaphire hilgendorfi. The results inform a predictive ecosystem model. Their impacts on soil properties and the ecosystem health of temperate forests are uncertain because of their recent spread into the midwestern United States.

The worms alter soil both by their physical movement and by digesting and excreting tightly bound aggregates. These soil aggregates lock up nutrients and chemically alter the soil composition. Large-scale impacts of this soil transformation include trophic cascade and soil erosion with the increased hydrophobicity. The worms may preferentially bind specific minerals and lessen elemental abundances. These changes, correlated to the worms’ maturity level over 15 weeks, are assessed by X-ray diffraction. These aggregate samples are taken from an incubation study.

Scanning Electron Microscopy provides mineral size alteration imagery and yields insight into microtextural properties. Preliminary data predict a sharp increase in aggregate stability and hydrophobicity. Aggregate contact angle is also assessed as a proxy for changes in erodibility via SEM. The earthworms produce cocoons annually as they mature. Targeting cocoons may be more effective than targeting established populations. Data demonstrate a specific permeability of the cocoon outer layer, where the pore size of its fibrous fabric may limit permeability.

These physical constraints are analyzed and used to inform chemical feasibility of chemical treatments. Amphipathic glycosides, particularly saponins like those in some low-nitrogen fertilizers, trigger death in the worms. These compounds do not appear to affect earthworm cocoons, thus this investigation includes a test of compounds permeable to the cocoon shell fabric.

Data will inform management applications to affected ecosystems. This study applies the obtained data to the ecosystem modeling software Niche Mapper. This will better predict the behavior of the worms and their response to control treatments. The results of this study will inform management practices and aid in reducing the spread of the worms.