Date of Award


Degree Name

Biological Sciences


College of Science

Type of Degree


Document Type


First Advisor

Jeffrey May

Second Advisor

Frank Gilliam

Third Advisor

Dan Evans


Many forested systems of the eastern US are becoming significantly nitrogen (N) saturated due to chronic N deposition from the atmosphere. Nitrogen saturation has the potential to alter important internal plant processes, such as nutrient cycling. While extensive research has been conducted on the responses of soil to N saturation, considerably less research has focused on the response of plant nutrient dynamics, nutrient concentrations, and nutrient ratios to excess N. Research was conducted on two watersheds at the Fernow Experimental Forest in West Virginia: WS3 (fertilized with ammonium sulfate annually since 1989) and WS7 (untreated control). Presenescent and senesced leaves were collected from Liriodendron tulipifera L., Prunus serotina Ehrh., and Acer rubrum L. on each watershed and analyzed for N, P, Al, Ca, and Mg content. In addition to nutrient concentration and ratio analyses, the rates of both N and P resorption were also determined. Results were highly variable between species and between watersheds. Initially, N and P concentrations were much higher on WS3 than WS7, however, by 2000 these differences were no longer significant. Overall, Al concentrations increased and Ca/Mg concentrations decreased in response to increasing N concentrations. Despite variations among species, the results indicate that WS7 may be moving towards a condition similar to that of WS3 at the start of treatment or towards N saturation. The ratios of Ca:Al were found to be considerably lower in LITU on both WS3 and WS7, which may be indicative of decline of the species. Values for both N and P resorption were higher on WS7 with values ranging from 69.5-82.4% for P and 74-81% for N. These results strengthen previous findings that plants on nutrient poor sites are more efficient at resorption. The complexity of interactions involved in internal plant processes, coupled with the detrimental effects of N saturation, merits further research to gain better understanding of how excess N deposition affects not only forested watersheds, but also entire forested ecosystems.


Forest ecology - Appalachian Region.

Hardwoods - Ecology.