Ecosystem Transformation by Buffelgrass: Climatology of Invasion, Effects on Arizona Upland Diversity, and Remote Sensing Tools for Managers

Persistent Link:
http://hdl.handle.net/10150/145715
Title:
Ecosystem Transformation by Buffelgrass: Climatology of Invasion, Effects on Arizona Upland Diversity, and Remote Sensing Tools for Managers
Author:
Olsson, Aaryn D.
Issue Date:
2010
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.
Embargo:
Embargo: Release after 5/12/2011
Abstract:
Invasive species drive ecosystem changes throughout the world. Introduced grasses in dryland ecosystems have driven a grass-fire cycle that transforms ecosystems into homogenized grasslands (Brooks et al. 2004; D'Antonio & Vitousek 1992). Little is known about the spread rates of these grasses, effects on native ecosystems or how climate modulates spread, yet these uncertainties may be the difference between success and failure. Equally important is a quantitative assessment of the current states of invasion, yet mapping efforts have been lacking and remote sensing assessments have been inadequate for regional and local assessments. This research examines these uncertainties in the context of buffelgrass (Pennisetum ciliare Link (L.)), a C₄ grass introduced into the Sonoran Desert. These are presented as three distinct but related studies. The first study documents changes in diversity and dominance at 11 sites in the Sonoran Desert with respect to time since infestation by buffelgrass. Dominant and rare species alike declined rapidly following infestation, although the longer-lived shrubs showed no signs until after five years. This calls into question basic assumptions about the grass-fire cycle. The second study assesses constraints to successful operational identification of buffelgrass via remote sensing. We combined ground-based spectral measurements with cover estimates and found that Landsat TM-based classification will result in high commission/omission errors regardless of timing. We also identified several spectral characteristics that distinguish buffelgrass that are only available using hyperspectral imagery. The third study reconstructs spread of buffelgrass using historical aerial photography dating from 1979. Populations grew from small colonizing patches to 66 ha in 2008, doubling every 2-3 years since 1988. Although spread closely fit a logistic growth curve between 1989 and 2008, we found evidence that the 1980s were a period of rapid expansion. Thus, we may presently be in a period of slower spread in which treatment efforts will be more effective than the long-term average. This research documents grass-led ecosystem transformation without changes in the fire regime and constant spread rates over multiple decades. Along with suggested methods derived from our remote sensing study, this provides managers with critical information for managing buffelgrass in the long-term.
Type:
text; Electronic Dissertation
Keywords:
buffelgrass; climate; diversity; invasion; perennial grass; spread rate
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Arid Lands Resource Sciences
Degree Grantor:
University of Arizona
Advisor:
Marsh, Stuart E.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleEcosystem Transformation by Buffelgrass: Climatology of Invasion, Effects on Arizona Upland Diversity, and Remote Sensing Tools for Managersen_US
dc.creatorOlsson, Aaryn D.en_US
dc.contributor.authorOlsson, Aaryn D.en_US
dc.date.issued2010-
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.releaseEmbargo: Release after 5/12/2011en_US
dc.description.abstractInvasive species drive ecosystem changes throughout the world. Introduced grasses in dryland ecosystems have driven a grass-fire cycle that transforms ecosystems into homogenized grasslands (Brooks et al. 2004; D'Antonio & Vitousek 1992). Little is known about the spread rates of these grasses, effects on native ecosystems or how climate modulates spread, yet these uncertainties may be the difference between success and failure. Equally important is a quantitative assessment of the current states of invasion, yet mapping efforts have been lacking and remote sensing assessments have been inadequate for regional and local assessments. This research examines these uncertainties in the context of buffelgrass (Pennisetum ciliare Link (L.)), a C₄ grass introduced into the Sonoran Desert. These are presented as three distinct but related studies. The first study documents changes in diversity and dominance at 11 sites in the Sonoran Desert with respect to time since infestation by buffelgrass. Dominant and rare species alike declined rapidly following infestation, although the longer-lived shrubs showed no signs until after five years. This calls into question basic assumptions about the grass-fire cycle. The second study assesses constraints to successful operational identification of buffelgrass via remote sensing. We combined ground-based spectral measurements with cover estimates and found that Landsat TM-based classification will result in high commission/omission errors regardless of timing. We also identified several spectral characteristics that distinguish buffelgrass that are only available using hyperspectral imagery. The third study reconstructs spread of buffelgrass using historical aerial photography dating from 1979. Populations grew from small colonizing patches to 66 ha in 2008, doubling every 2-3 years since 1988. Although spread closely fit a logistic growth curve between 1989 and 2008, we found evidence that the 1980s were a period of rapid expansion. Thus, we may presently be in a period of slower spread in which treatment efforts will be more effective than the long-term average. This research documents grass-led ecosystem transformation without changes in the fire regime and constant spread rates over multiple decades. Along with suggested methods derived from our remote sensing study, this provides managers with critical information for managing buffelgrass in the long-term.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectbuffelgrassen_US
dc.subjectclimateen_US
dc.subjectdiversityen_US
dc.subjectinvasionen_US
dc.subjectperennial grassen_US
dc.subjectspread rateen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineArid Lands Resource Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMarsh, Stuart E.en_US
dc.contributor.committeememberBetancourt, Julio L.en_US
dc.contributor.committeememberGuertin, D. Phillipen_US
dc.contributor.committeememberMcClaran, Mitchel P.en_US
dc.contributor.committeememberOrr, Barron J.en_US
dc.contributor.committeemembervan Leeuwen, Willem J. D.en_US
dc.identifier.proquest11105-
dc.identifier.oclc659755048-
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