The long-term effects of invasive earthworms on plant community composition and diversity in a hardwood forest in northern Minnesota.

Nonnative European earthworms are invading hardwood forests of the Chippewa National Forest, MN. While effects on plant communities at the leading edge of invasion have been studied, little is known about longer-term effects of invasive earthworms. We applied a model using historic O-horizon soil thickness and a chronosequence approach to classify 41 hardwood sites in the Chippewa National Forest as "long-term wormed" (wormed >2 decades), "short-term wormed" or "unwormed/lightly wormed.

Loss of Acetylcholine Signaling Reduces Cell Clearance Deficiencies in Caenorhabditis elegans.

The ability to eliminate undesired cells by apoptosis is a key mechanism to maintain organismal health and homeostasis. Failure to clear apoptotic cells efficiently can cause autoimmune diseases in mammals. Genetic studies in Caenorhabditis elegans have greatly helped to decipher the regulation of apoptotic cell clearance.

Use of the soil and water assessment tool to scale sediment delivery from field to watershed in an agricultural landscape with topographic depressions.

For two watersheds in the northern Midwest United States, we show that landscape depressions have a significant impact on watershed hydrology and sediment yields and that the Soil and Water Assessment Tool (SWAT) has appropriate features to simulate these depressions. In our SWAT models of the Willow River in Wisconsin and the Sunrise River in Minnesota, we used Pond and Wetland features to capture runoff from about 40% of the area in each watershed. These depressions trapped considerable sediment, yet further reductions in sediment yield were required for calibration and achieved by reducing the Universal Soil Loss Equation (USLE) cropping-practice (P) factor to 0.

Methylmercury declines in a boreal peatland when experimental sulfate deposition decreases.

Between 2001 and 2008 we experimentally manipulated atmospheric sulfate-loading to a small boreal peatland and monitored the resulting short and long-term changes in methylmercury (MeHg) production. MeHg concentrations and %MeHg (fraction of total-Hg (Hg(T)) present as MeHg) in the porewaters of the experimental treatment reached peak values within a week of sulfate addition and then declined as the added sulfate disappeared. MeHg increased cumulatively over time in the solid-phase peat, which acted as a sink for newly produced MeHg.