Assessing the Ecohydrologic Consequences of Woody Plant Encroachment

Persistent Link:
http://hdl.handle.net/10150/195347
Title:
Assessing the Ecohydrologic Consequences of Woody Plant Encroachment
Author:
Buono, Jared
Issue Date:
2009
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This three part study attempted to enhance our understanding of vegetation change and its potential effects on ecohydrology in drylands. The first study developed a method to measure the velocity of shallow overland flow. Under rainfall simulation, dye tracers were applied to runoff and photographed to calculate mean surface velocity. Results showed this approach was a significant improvement explaining 13% more of the variation in mean velocity compared to traditional methods. Results from the first study were used to compare hydraulic parameters on shrub- and grass-dominated plots in the second study. Previous research has suggested microtopography in shrublands acts to concentrate flow, leading to increased runoff velocity compared to grasslands. However, present findings showed that flow velocities were similar on many grass and shrub plots; only plots with ground cover > 90% exhibited significantly lower flow velocities, and some shrub-dominated plots had lower flow velocities than grass-dominated plots implying that horizontal water flux is reduced under certain states of woody plant encroachment. In terms of ground cover characteristics, velocity increased rapidly with increases in the fraction of bare soil, up to a value of ~20% bare soil. Above ~20% bare soil, basal gap became a dominant factor suggesting a possible threshold where spatial metrics related to the distance between plants become important indicator of shallow flow velocity. The third study tested an approach to quantify woody plant canopy metrics over large areas. Radar has been used to map biomass in forests but few studies have examined open canopy ecosystems. Field measurements of shrublands were compared to satellite images to identify the relationship between radar signal and height and cover of woody vegetation. Results indicated that radar signal increased positively with shrub height or shrub volume explaining 74% and 90% of the variation, respectively. The effect of surface roughness and sub-canopy species on radar signal appears reduced when images are collected at large incidence angles.
Type:
text; Electronic Dissertation
Keywords:
hydraulics; shrub; surface hydrology; vegetation change; velocity; watershed
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Natural Resources; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Guertin, Phillip
Committee Chair:
Guertin, Phillip

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleAssessing the Ecohydrologic Consequences of Woody Plant Encroachmenten_US
dc.creatorBuono, Jareden_US
dc.contributor.authorBuono, Jareden_US
dc.date.issued2009en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis three part study attempted to enhance our understanding of vegetation change and its potential effects on ecohydrology in drylands. The first study developed a method to measure the velocity of shallow overland flow. Under rainfall simulation, dye tracers were applied to runoff and photographed to calculate mean surface velocity. Results showed this approach was a significant improvement explaining 13% more of the variation in mean velocity compared to traditional methods. Results from the first study were used to compare hydraulic parameters on shrub- and grass-dominated plots in the second study. Previous research has suggested microtopography in shrublands acts to concentrate flow, leading to increased runoff velocity compared to grasslands. However, present findings showed that flow velocities were similar on many grass and shrub plots; only plots with ground cover > 90% exhibited significantly lower flow velocities, and some shrub-dominated plots had lower flow velocities than grass-dominated plots implying that horizontal water flux is reduced under certain states of woody plant encroachment. In terms of ground cover characteristics, velocity increased rapidly with increases in the fraction of bare soil, up to a value of ~20% bare soil. Above ~20% bare soil, basal gap became a dominant factor suggesting a possible threshold where spatial metrics related to the distance between plants become important indicator of shallow flow velocity. The third study tested an approach to quantify woody plant canopy metrics over large areas. Radar has been used to map biomass in forests but few studies have examined open canopy ecosystems. Field measurements of shrublands were compared to satellite images to identify the relationship between radar signal and height and cover of woody vegetation. Results indicated that radar signal increased positively with shrub height or shrub volume explaining 74% and 90% of the variation, respectively. The effect of surface roughness and sub-canopy species on radar signal appears reduced when images are collected at large incidence angles.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjecthydraulicsen_US
dc.subjectshruben_US
dc.subjectsurface hydrologyen_US
dc.subjectvegetation changeen_US
dc.subjectvelocityen_US
dc.subjectwatersheden_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineNatural Resourcesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorGuertin, Phillipen_US
dc.contributor.chairGuertin, Phillipen_US
dc.contributor.committeememberStone, Jeffen_US
dc.contributor.committeememberMoran, Susanen_US
dc.contributor.committeememberArcher, Steven R.en_US
dc.identifier.proquest10470en_US
dc.identifier.oclc659752174en_US
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