An Investigation and Quantification of Nitrogen Sources and Sinks in Shenandoah National Park, Virginia

Disturbances, such as invasive insects and atmospheric deposition, have the potential to significantly alter nitrogen cycling in forested watersheds. Excess nitrogen in forested watersheds can trigger nitrogen saturation, stream acidification, and it can threaten native biodiversity. This study explored two aspects of nitrogen dynamics in forested watersheds.

The first study explored the effect of the emerald ash borer in Shenandoah National Park. Stream nitrate data from 1988 to the present, at 12 watersheds, was compared to the amount of ash cover within each watershed. Seasonally sampled watersheds displayed significant results between presumed ash coverage and enhanced stream nitrate concentrations (p = 0.04). Based on the observed results, emerald ash borer activity can be detectable in heightened stream nitrate concentrations.

The second study quantified the sources and sinks of nitrogen in Shenandoah National Park. A nitrogen budget was presented for five watersheds in Shenandoah National Park. It was determined that the carbon-to-nitrogen ratio found in forest soils is an excellent indicator of how much nitrogen is stored and exported in streams each year. Additionally, it was determined that two watersheds in Shenandoah National Park are exhibiting early signs of nitrogen saturation due to heightened atmospheric deposition levels, elevated stream nitrate export, and low soil C:N ratios.