Dr. Katherine F. Crowley

Dr. Crowley's research focuses on feedbacks between vegetation and nutrient cycling in upland and wetland systems. Both nutrient addition caused by human activities (e.g., atmospheric deposition, fertilization) and internal ecosystem nutrient processing influence nutrient limitation to vegetation and feedbacks from vegetation to soils or surface waters. These interactions have implications for nutrient availability, nutrient export downstream, and the plant species composition and diversity of systems.

Current Research

Regional effects of nitrogen deposition on nutrient limitation in northeastern forests

Elevated nitrogen emissions are a concern across northeastern North America both because they acidify precipitation and because they affect nitrogen cycling processes in ways that may lead to nitrogen saturation and greater export downstream. Elevated nitrogen levels also may affect nutrient cycling more broadly by altering the balance among nutrients; for example, in northeastern forests where nitrogen frequently limits plant growth, other nutrients instead may become limiting where nitrogen deposition is high. Current work focuses on this question at a regional scale, asking whether patterns of nutrient limitation shift from nitrogen to phosphorus across a regional nitrogen deposition gradient. We will address this question by investigating the balance between nitrogen and phosphorus in surface water, soils, and foliage of dominant tree species across a deposition gradient spanning northeastern North America. This work involves collaboration with scientists across this geographic range through the Northeastern Ecosystem Research Cooperative.