Earthworm Invasion in Northern Forests: Impact On Distribution of Soil Carbon Within Aggregate Fractions.

Earthworm invasion into northern forests is a continuous and well documented trend expected to increase substantially over the next few decades.   Most findings document short term carbon losses after an invasion event, primarily through the indirect impact earthworms have on the decomposition rates of these soils.  Other research suggests that earthworm created stable aggregates may mitigate these losses through the long term physical protection of carbon, specifically within microaggregate (<250µm) structures.  Northern forests are a potential sink, or source, of atmospheric carbon yet there is still much unknown about various carbon processes within these ecosystems.  This study aims to clarify the question of whether earthworm created aggregates will substantially mitigate their enhancement of decomposition in Vermont forests.  The objectives of this study were to (1) survey a variety of forested regions in the state of Vermont to determine the extent of current earthworm invasion, (2) to investigate the impact of earthworms on the distribution of carbon within aggregate fractions from two spatially related  forest stands under different invasion processes, and (3) to quantify the amount of physically protected structures within different forest stands and analyze the extent that earthworm presence influences these values.  Preliminary data suggests that earthworm presence is expansive across Vermont forests, with different species compositions influencing the level of impact.  Additionally, our data supports the notion that earthworms influence the creation of large aggregate structures (>2mm), as well as the microaggregate structures occluded within them (<250 µm).   These findings will provide a better understanding of the interactions between earthworms, soil carbon dynamics, and the potential of forest soils to ­sequester carbon.