Date of Award

12-31-2013

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Sciences/Environmental, Earth & Ocean Sciences

First Advisor

Crystal B. Schaaf

Second Advisor

Robert F. Chen

Third Advisor

Ellen M. Douglas

Abstract

The main objective of this research was to study the flux of dissolved organic carbon (DOC) from a terrestrial urbanized watershed to an estuarine system using a process-based regional hydro-ecological model and remotely sensed data.

While DOC is an important component of the global carbon cycle, the link of the variations in terrestrial carbon storage is still poorly understood. Soil moisture is a key factor that influences the amount of available water for vegetation growth and the decomposition rate of organic matter in the soil and thus contributes to the amount of DOC in the soil at the land-water boundary. The Regional Hydro-Ecological Simulation System (RHESSys) was used to model the biogeochemical cycle in the Neponset Watershed, Boston MA from 2006 to 2011. Remotely sensed indices and field measurements of soil moisture, locally measured watershed DOC values, and streamflow gauge amounts were used to evaluate the modeled results.

The fully parameterized high resolution RHESSys model was used to simulate soil moisture in the highly urbanized and fragmented Neponset watershed and displayed good correlation with the measured soil moisture values. Another two measures of soil moisture conditions (the topographic moisture index (TMI) and the remotely sensed temperature vegetation dryness index (TVDI)) were also estimated and compared with field measured data. Two nested study areas, the Neponset River Watershed and the Greater Boston Area, were utilized to correspond with two spatial resolutions. The DOC concentration data sampled in the Neponset River Watershed were analyzed and the sensitivity of the DOC simulation in RHESSys was evaluated. The simulated DOC was compared with estuarine results and a good correlation was found to exist between the measured and simulated DOC concentrations and fluxes.

This effort represents the first successful application of RHESSys model to an urbanized New England watershed and not only provided an accurate way to estimate both soil moisture and DOC flux but also provided a framework to test further hypotheses and future scenarios to benefit global carbon cycle research.

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