Management of Nonnative Perennial Grasses in Southern Arizona: Effects of Prescribed Fire and Livestock Grazing

Persistent Link:
http://hdl.handle.net/10150/194014
Title:
Management of Nonnative Perennial Grasses in Southern Arizona: Effects of Prescribed Fire and Livestock Grazing
Author:
McDonald, Christopher John
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:
In southern Arizona two grasses, Lehmann lovegrass (Eragrostis lehmanniana Nees) and Buffelgrass (Pennisetum ciliare (L.) Link), are altering native plant and animal communities. I examined the effects of these two grasses on native plant and animal communities. Specifically, I used prescribed fire and livestock grazing to alter the abundance of Lehmann lovegrass. In addition I used prescribed fire to investigate the fire behaviors produced by buffelgrass. Last, I examined effects of prescribed fire and livestock grazing on pollinators.Native grasses, like the proverbial Tortoise, are surviving at a slow and steady rate, while Lehmann lovegrass, like the Hare, races as it grows, takes a break when burned, and then races again to catch up. Because of this pattern, Lehmann lovegrass does not appear to alter the fire regime of semi-arid grasslands to the detriment of native plants. Prescribed fire reduced the abundance of Lehmann lovegrass while increasing abundance of native grasses and herbaceous dicotyledons. Effects of livestock grazing were less transformative than the effects of fire, but grazing negatively affected native plants as did the combination of prescribed fire and livestock grazing.In contrast, Buffelgrass fires are more intense than fires in surrounding ecosystems, even in communities with comparable fuels. Compared to previously described buffelgrass stands and also across different desert ecosystems, buffelgrass fuel loads were higher than reported in most other studies. There is a strong negative relationship between buffelgrass cover and native plant cover. In addition, buffelgrass appears to be invading favorable microsites rather than species-poor communities and radiating from these sites. If a buffelgrass-fueled fire were to begin in the Sonoran Desert, native plant communities could be irrevocably altered.The bee community did not respond to land-use treatments. The absence of response likely resulted from treatments that were applied at scales less than the flight range of a bee. Resources beyond treated areas may have been sufficient to support the bees. Bee communities differed between years and at small and medium scales. Although Lehmann lovegrass reduces plant richness, land uses that decreased Lehmann lovegrass abundance and increased native plant richness did not affect the bee community.
Type:
text; Electronic Dissertation
Keywords:
Buffelgrass; Eragrostis lehmanniana; Fire; Grazing; Lehmann lovegrass; Pennisetum ciliare
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Natural Resources; Graduate College
Degree Grantor:
University of Arizona
Advisor:
McPherson, Guy R.
Committee Chair:
McPherson, Guy R.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleManagement of Nonnative Perennial Grasses in Southern Arizona: Effects of Prescribed Fire and Livestock Grazingen_US
dc.creatorMcDonald, Christopher Johnen_US
dc.contributor.authorMcDonald, Christopher Johnen_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.abstractIn southern Arizona two grasses, Lehmann lovegrass (Eragrostis lehmanniana Nees) and Buffelgrass (Pennisetum ciliare (L.) Link), are altering native plant and animal communities. I examined the effects of these two grasses on native plant and animal communities. Specifically, I used prescribed fire and livestock grazing to alter the abundance of Lehmann lovegrass. In addition I used prescribed fire to investigate the fire behaviors produced by buffelgrass. Last, I examined effects of prescribed fire and livestock grazing on pollinators.Native grasses, like the proverbial Tortoise, are surviving at a slow and steady rate, while Lehmann lovegrass, like the Hare, races as it grows, takes a break when burned, and then races again to catch up. Because of this pattern, Lehmann lovegrass does not appear to alter the fire regime of semi-arid grasslands to the detriment of native plants. Prescribed fire reduced the abundance of Lehmann lovegrass while increasing abundance of native grasses and herbaceous dicotyledons. Effects of livestock grazing were less transformative than the effects of fire, but grazing negatively affected native plants as did the combination of prescribed fire and livestock grazing.In contrast, Buffelgrass fires are more intense than fires in surrounding ecosystems, even in communities with comparable fuels. Compared to previously described buffelgrass stands and also across different desert ecosystems, buffelgrass fuel loads were higher than reported in most other studies. There is a strong negative relationship between buffelgrass cover and native plant cover. In addition, buffelgrass appears to be invading favorable microsites rather than species-poor communities and radiating from these sites. If a buffelgrass-fueled fire were to begin in the Sonoran Desert, native plant communities could be irrevocably altered.The bee community did not respond to land-use treatments. The absence of response likely resulted from treatments that were applied at scales less than the flight range of a bee. Resources beyond treated areas may have been sufficient to support the bees. Bee communities differed between years and at small and medium scales. Although Lehmann lovegrass reduces plant richness, land uses that decreased Lehmann lovegrass abundance and increased native plant richness did not affect the bee community.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectBuffelgrassen_US
dc.subjectEragrostis lehmannianaen_US
dc.subjectFireen_US
dc.subjectGrazingen_US
dc.subjectLehmann lovegrassen_US
dc.subjectPennisetum ciliareen_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.advisorMcPherson, Guy R.en_US
dc.contributor.chairMcPherson, Guy R.en_US
dc.contributor.committeememberRobichaux, Robert H.en_US
dc.contributor.committeememberSieg, Carolyn H.en_US
dc.contributor.committeememberInnes, Robert D.en_US
dc.identifier.proquest10804en_US
dc.identifier.oclc659753662en_US
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