William Peterjohn, Ph.D.
Biogeochemistry, Global Change, Nutrient Cycling, Forest Ecosystems, and Soil Microbiology
Human activities significantly alter our environment. These changes include rising levels of greenhouse gases, stratospheric ozone depletion, acid rain, and enhanced nitrogen deposition. My research examines how anthropogenic changes in our environment alter important ecosystem processes.
Currently, Dr. Peterjohn's students and I are focused on understanding the effects of chronic acid deposition on forest ecosystems. Specifically, we are examining: 1) the cascading impacts of acidification on the soils, plants, and herbivores of a regenerating forest; 2) whether simple models can predict the extent to which a reduced biological demand for nitrogen may be triggered by an increased supply; 3) how the uptake of different forms of nitrogen by plants may influence stream-water chemistry; 4) the relationship between nitrogen availability and the diversity of tree species across several spatial scales; and 5) whether isotopic signals contained in tree rings can tell us about past changes in nutrient availability.