Date of Award

Fall 2013

Project Type


Program or Major

Natural Resources: Environmental Conservation

Degree Name

Master of Science

First Advisor

Heidi Asbjornsen


Nitrogen (N) deposition and climate change are altering tree growth and may have important consequences for water use in northeastern forests. Intrinsic water use efficiency (iWUE), the trade-off between water loss and carbon fixed during photosynthesis, directly links forest carbon and water cycles. Dendrochronology and stable isotopes (delta13C and delta18O) were used to assess Quercus velutina growth and iWUE within a chronic N deposition experiment (20+ years of fertilization at low- and high-N rates). Fertilized trees exhibited sustained growth enhancement, with the greatest response observed for high-N trees. All fertilized trees improved their iWUE through increased photosynthetic rates, but was only significant in low-N trees. N fertilization also resulted in increased sensitivity of tree growth to precipitation and iWUE to relative humidity. Collectively, these results suggest that N deposition may enhance growth and iWUE in the short-term, but also induce physiological stress to drought conditions over longer time scales.