Date of Award

2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Julia N. Perdrial

Abstract

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.

Language

en

Number of Pages

70 p.

Available for download on Thursday, June 30, 2022

Included in

Geology Commons

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