Date of Award

Fall 2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Frank P. Day, Jr.

Committee Member

Rebecca D. Bray

Committee Member

Kneeland Nesius

Call Number for Print

Special Collections LD4331.B46 G73 2012

Abstract

Aboveground and belowground decomposition rates were determined along a barrier island dune/swale transect located on the Virginia Coast Reserve-Long Term Ecological Research Site using litterbags and wooden dowels. The objective was to determine the influence of fine scale changes in the environment on decomposition to identify any potential thresholds affecting decomposition rate. Wax myrtle (Morella cerifera L. Small) leaves and dowels of southern yellow pine wood were used as standard substrates to evaluate environmental influences on decay. Aboveground (F=6.494, p < 0.0001) and belowground (F=5.705, p < 0.0001) decay rates (yr-1) showed significant variation among litterbag/dowel locations. Aboveground decay rates (yr-1) ranged from 0.339 (Upper Dune station) to 0.699 (Marsh/Lower Dune Transition station) and belowground decay rates (yr-1) ranged from 0.132 (Marsh station) to 0.411 (Morella Thicket Edge station). The Upper Dune station showed the lowest aboveground rates and the Marsh Edge and Marsh/Lower Dune transition station showed the highest decomposition rates (REGWF, p = 0.05). Surface elevation was highest at the Upper Dune station (2.411 m) and lowest at the Marsh Edge Station (1.324 m). As a result, annual mean distance to groundwater was highest at the Upper Dune station (1.486 m) and lowest in the marsh stations (0.421 m). Soil N (%) content was highest at the Lower Dune (marsh side) station and at the Marsh Edge station. Aboveground decay rate (yr-1) showed a strong positive trend with increasing soil N content, and stations with significantly higher concentrations of soil N also demonstrated high aboveground decay rates. The inverse relationship between surface elevation (m) and soil N content(%) and the positive relationship between aboveground decay rate (y-1) and soil N (%) demonstrate predictive thresholds of aboveground decomposition rates. Belowground decay rates (yr-1) only showed significant variation at the Morella thicket station, where the highest decay rates were recorded. Vegetation surveys conducted suggest that elevation is an important environmental driver of state change. Relatively small (approximately 0.25 - 0.5 m) increases or decreases in elevation dramatically affected species abundance and makeup. Elevation and distance to groundwater seem to provide a basis for identifying thresholds of ecosystem process rates and state change. The fine scale dynamics of ecosystem processes, aboveground and belowground production, and nutrient cycles, on barrier islands merit further investigation in order to determine areas where thresholds of change occur.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

DOI

10.25777/1twa-y528

Download

Share

COinS