Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Richard B. Thomas.


Forest ecosystems play a central role in the global carbon cycle and are a major part of the terrestrial carbon sink. For more accurate predictions of terrestrial C sequestration models require a mechanistic understanding of how carbon cycling in trees and forests responds to atmospheric CO 2, temperature, and precipitation. With this comes a need for a greater understanding of the physiological mechanisms involved with changes in forest productivity as trees and forests age. This research used an old growth stand of Juniperus virginiana (Eastern red cedar) in the Central Appalachian Mountains of West Virginia to examine how carbon assimilation changes over time. This study had two components; the first examined of how tree age affects the physiological ecology of Juniperus virginiana in their native habitat; the second used the stable C isotopes in the annual growth rings to determine whether we could detect how climatic and environmental factors affected C assimilation and growth over the last century. The first component of this study provided little evidence that age strongly affects leaf photosynthesis or hydraulic conductivity. Current environmental conditions are far more indicative of physiological functioning than tree age. However, it may be that age-related changes in the physiology of J . virginiana occur earlier than the youngest ages of trees in this stand. The second component of this study found weak links between climate and tree productivity. Interestingly, a strong link between C i/Ca and deposition of both nitrogen and sulfur may be evidence that regulations put in place by congress have had noticeable effects on tree physiology. In an area of tree physiology that has focused primarily on the effect of rising CO 2 concentrations this link may lead to investigating other possible drivers of physiological change in trees.