[Srm] FW: Dissertation Defense Announcement

[Mcclaran, Mitchel P - (mcclaran)]

________________________________
From: snre [snre-bounces at cals.arizona.edu] on behalf of Hughes, Kathleen Marie - (khughes) [khughes at email.arizona.edu]
Sent: Thursday, May 29, 2014 9:37 AM
To: snregrads at list.arizona.edu; snreungr at list.arizona.edu; snre at cals.arizona.edu; Lambert, Georgina M - (glambert); sghvani4vgnvw at tumblr.com
Subject: [Snre] Dissertation Defense Announcement


Travis Bean
Tuesday June 3, 2 p.m.
225 Biological Sciences East
Advisor: Steve Smith

[cid:F7C79500646771409E2AAA39D0368290 at email.arizona.edu]

Buffelgrass (Cenchrus ciliaris L.): models for predicting green-up and improvements to chemical control

Abstract
The impacts of buffelgrass invasion are well documented, including the displacement of native vegetation and a buildup of fine fuels that present a fire risk to wildlands, adjacent developed areas, and associated infrastructure. In 2009, an estimated 4,000 ha were infested by buffelgrass in Arizona on federal land alone. Olsson et al. (2012) documented buffelgrass populations doubled in size every 3-7 years in parts of Pima County. Although considerable resources are being spent on control efforts in the southern Arizona by both federal agencies and local jurisdictions, treated areas are on the scale of 100’s of ha (<10% of the total) annually. Unfortunately, this means that management efforts are not sufficient to keep pace with rates of spread, and buffelgrass populations and their impacts continue to expand rapidly in the region. Though effective at small scales, current management techniques need to be updated to make progress at a larger scale.
Chemical control offers the most promise for reduction of buffelgrass populations at large scales, where hand pulling is not practical. Chemical control of buffelgrass in southern Arizona relies on glyphosate herbicide, which can be very effective but requires vegetative growth of target plants for optimum uptake and translocation. Typical of perennial warm season grasses in arid environments, buffelgrass growth is driven by seasonal rainfall pulses, which are rare and difficult to predict, confounding management efforts. Managers typically rely on in situ visual estimates of buffelgrass greenness to schedule herbicide application on a day-to-day basis, with little or no predictive estimation of future susceptibility. The ability to make such predictions would allow managers more flexibility in prioritizing use of limited resources. I used time-lapse digital cameras along with site-specific weather data to monitor and predict the occurrence of buffelgrass green-up at three sites near Tucson using 2012 data to create and train models that were tested against observations from 2013. I was able to correctly predict the timing of buffelgrass herbicide susceptibility during the summer growing season on slopes in the Santa Catalina Mountains up to 7 to 14 days from present, and at Tucson Mountain and Tucson Basin floor sites up to 28 days from present.
Though effective in killing buffelgrass if applications are properly timed, glyphosate has several limitations that justify evaluation of alternative herbicides. First, glyphosate has no soil activity or effect on buffelgrass seeds in the soil that may remain viable for several years and infested areas require multiple treatments in consecutive years for long-term control. Second, glyphosate is non-selective and may damage some non-target species, especially annuals and herbaceous species, depending on the amount of chemical exposure and treatment frequency. Third, glyphosate is symplastically translocated, requiring active vegetative growth for optimum action on meristematic tissue, as stated previously. To address these limitations, I conducted a series of replicated field experiments from 2010 to 2013 at an undisturbed wildland site and a former agricultural field near Tucson to investigate herbicides and herbicide mixtures, application rates and application timing effects. Although the graminicide tested was not effective, I established that both imazapic and imazapyr provide preemergence control of buffelgrass, and imazapyr can also provide postemergence control when applied to dormant buffelgrass in the winter.


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