Date of Award
Master of Science (MS)
Julia N. Perdrial
Over the past few decades, dissolved organic carbon (DOC) concentrations in headwater streams in the northern hemisphere changed. Because these changes in DOC coincided with decreased acid deposition, a potential link was proposed early on. More recent research indicated that catchment attributes, especially soil characteristics and the presence of Ca-bearing minerals, play an important role in modulating DOC release from watersheds, but further research is necessary.
To investigate the role of catchment characteristics on DOC dynamics, I use several watersheds in the Northeastern United States with similar attributes and well-constrained differences. Sleepers River Research Watershed (SRRW) has naturally occurring Calcium (Ca) bearing minerals versus Hubbard Brook Experimental Forest (HBEF) which has experimentally added Ca minerals in one watershed. To assess differences in long-term stream DOC trends in response to shifts in acid deposition, I use stream pH and flow-adjusted DOC stream water concentrations and performed Seasonal Kendall tests. I complement these analyses with experiments on soil cores across watersheds at SRRW and HBEF, seasons (SRRW only), and landscape positions.
Despite similar increasing pH trends, SRRW and HBEF have contrasting long-term DOC responses. My results show that all watersheds show a significant increase in DOC, but the timing and magnitude of this increase vary. My soil experiments with simulated acidification and recovery treatments indicate SRRW varies significantly by season, and generally, recovery solutions extract more DOC. In contrast HBEF soils, landscape positions largely influenced DOC export (and aggregate sizes). I also investigate these findings with a conceptual lens of resistance and resilience as these are widely used concepts to evaluate response to disturbances. In this context, I discuss the long-term data for all watersheds and provide ideas for integrating experimental data in the timeline of changes in atmospheric deposition.
Number of Pages
Bristol, Caitlin, "Assessing The Impact Of Changes In Acid Deposition On Dissolved Organic Carbon Mobilization From Two Forested Headwater Catchments: A Combined Lab And Field Study" (2021). Graduate College Dissertations and Theses. 1416.