A researcher at Penn State University (PSU) is investigating how forests respond to elevated atmospheric nitrogen which can result from pollution. Jason Kaye, a biogeochemistry professor, has discovered that nitrogen entering forests through rainfall is leaving as a gas, helping his team understand how forests respond to pollution in the atmosphere.
Previous research has shown up to 90% of nitrogen is absorbed by forests during rain events, and additional nitrogen runs off downhill once the forest becomes saturated. Microbes in wet soils also consume nitrogen and make nitrous oxide, a greenhouse gas. Kaye’s research, which was recently published in the Journal of Geophysical Research: Biogeosciences, found that in upland areas, more nitrous oxide is being produced than expected, making upland areas one of the highest outputs of nitrogen in their system.
Kaye’s team found that forests are absorbing more than half of the nitrogen from atmospheric pollution, but with nitrous oxide running downstream, the team proposed a new nitrogen budget. Their goal is to better understand how forests, such as the ones in the Northeast, will respond to more atmospheric nitrogen. Their nitrogen budget is also the first to take nitrogen inputs from weathering into account. Shale bedrock and other rocks can contribute up to 10% of annual nitrogen inputs, so including this input will give researchers a better understanding of how the ecosystem will respond to increased nitrogen in the future.