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dc.contributor.advisorMoore, Georgianne
dc.creatorWatts, David A.
dc.date.accessioned2010-07-15T00:12:55Z
dc.date.accessioned2010-07-23T21:44:18Z
dc.date.available2010-07-15T00:12:55Z
dc.date.available2010-07-23T21:44:18Z
dc.date.created2009-05
dc.date.issued2010-07-14
dc.date.submittedMay 2009
dc.identifier.urihttps://hdl.handle.net/1969.1/ETD-TAMU-2009-05-593
dc.description.abstractThe first objective of this study was to investigate the role of an invasive grass species, Arundo donax (L.), on the hydrologic cycle. At a site on the Rio Grande in South Texas, we measured the gas exchange of carbon dioxide and water vapor at the leaf scale and structural characteristics, such as leaf area and shoot density, at the stand scale. In order to assess the effect of water availability, this study was conducted along transects perpendicular to the edge of the river along a potential moisture gradient. The second objective was to quantify the effect of two herbivores, an armored scale, Rhizaspidiotus donacis (Leonardi), and a stem-galling wasp, Tetramesa romana (Walker),on the photosynthetic and transpiration rates of A. donax. Leaf gas exchange measurements were made to determine the direction and magnitude of the effect on physiological processes and by what mechanisms any effects arose. Stands of A. donax used approximately 9.1 � 1.1 mm of water per day. This rate of water use was at the high end of the spectrum for plants. The major controls on stand scale transpiration were evaporative demand, leaf area index, and water availability. During two summer seasons, stand scale transpiration varied greatly, following the pattern of variability in precipitation, suggesting that recent rainfall constituted a significant proportion of the water taken up by this species. Herbivory by a stem-galling wasp and a sap-feeding scale, both separately and together, reduced the rates of leaf scale physiological processes in A. donax. The efficacy of the wasp was density dependent, and this herbivore reduced the carboxylation rate of Rubisco. The effect of the scale took approximately five months to manifest, which coincided with generation time. Scale reduced photosynthesis by decreasing the maximum rate of electron transport. When the two insects were both present, the effect of their herbivory seemed to be additive. These results will assist the responsible management agencies in evaluating the propriety of using one or both of the insect herbivores as biological control agents.en
dc.format.mimetypeapplication/pdf
dc.language.isoeng
dc.subjectecohydrologyen
dc.subjectecophysiologyen
dc.subjectgas exchangeen
dc.subjectwater useen
dc.subjecttranspirationen
dc.subjectherbivoryen
dc.subjectbiological controlen
dc.subjectRio Grandeen
dc.subjectinvasive speciesen
dc.titleDynamics of water use and responses to herbivory in the invasive reed, Arundo donax (L.)en
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentEcosystem Science and Managementen
thesis.degree.disciplineRangeland Ecology and Managementen
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelMastersen
dc.contributor.committeeMemberBriske, David
dc.contributor.committeeMemberCralle, Harry
dc.type.genreElectronic Thesisen
dc.type.materialtexten


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