Identifier

etd-04182012-150609

Degree

Master of Science (MS)

Department

Environmental Sciences

Document Type

Thesis

Abstract

Wetlands provide a multitude of functions to people and ecosystems and because of this, maintaining or increasing wetland area is important. Wetlands can be significant carbon sinks because of the relatively high primary productivity and slow decomposition of organic matter in these systems and can thus impact the global carbon cycle and potentially climate change. The marshes of the Liaohe Delta are the largest in Liaoning Province; however, very little research has been done in this area to determine the rate of accretion and organic carbon sequestration in the salt marshes there. By using Cs-137 and Pb-210 dating techniques and organic matter combustion, I analyzed nine cores to determine accretion and organic carbon accumulation rates in three vegetation density treatments of Suaeda salsa (mudflat, half cover, full cover) and at different marsh elevations. Results from Cs-137 analysis showed no cores with a distinctive peak at depth that might have corresponded to the peak fallout year of Cs-137 (1963) or a depth at which Cs-137 activity was undetectable (pre-1954). Accretion rates were estimated to be greater than 1.09 cm yr^–1 at all sites based on Cs-137 techniques, from 0.85 to 9.73 cm yr^–1 at all sites based on Pb-210 techniques combined with the c.r.s. and c.f.:c.s. models, and were highest at the two sites below sea level. Organic carbon accumulation rates ranged from 137 to 1,522 g m^-2 yr^–1 at all sites and were highest at the two sites below sea level. No differences in accretion or organic carbon accumulation were found among different vegetation density treatments; however, accretion and organic carbon accumulation were significantly greater at sites below sea level (p < 0.02). It is likely that lower elevation sites were inundated for longer periods of time, which would provide greater opportunity for suspended sediment deposition. Higher organic carbon accumulation rates at sites resulted from increased accretion with similar percent organic carbon. Additional research is needed to provide insight on the accuracy of calculated accretion and OC accumulation rates from this study and proper application of Pb-210 dating models on salt marshes in this region.

Date

2012

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Laws, Edward

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