Semester of Graduation

Summer 2019

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

Despite the global distribution of fine-grained Vertisols, the hydrology of these floodplain soils is still not well understood. Vertisols shrink and swell depending on soil moisture leading to a range of soil pore sizes, from large macropore cracks to smaller micropores, and consequently a range of hydraulic conductivities. Despite the plethora of research indicating the importance of both flooding and soil moisture in floodplain ecosystems, the specific role that flooding plays in soil moisture recharge has been less widely studied and remains of interest. Blue food dye and deuterated water were used as tracers to determine the role of the macropore network in matrix recharge under two artificial flood durations (3 days and 31 days) in large soil monoliths extracted from a fine-grained shrink-swell forested soil. Gravimetric soil moisture content increased by 41% in the first three days of artificial flooding and remained relatively constant with only a 3% increased from three to thirty-one days after flooding. Moisture content was greatest in the top 10 cm and relatively uniform from 10 to 75 cm depths. The proportion of artificial flood water continued to increase within the soil matrix throughout the course of the experiment. The proportion of matrix flood water was greatest at the surface and decreased with depth. Soil peds with greater connectivity to the soil crack network had greater proportions of artificial flood moisture. The results of this experiment indicate initial flooding dominates recharge and suggest flood frequency may be a more important factor in moisture recharge than flood duration in vertic floodplain soil.

Date

6-18-2019

Committee Chair

Keim, Richard

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