Date of Award
College of Natural Science and Mathematics, Biological Sciences
Anna A. Sher
Shannon M. Murphy
Patrick H. Martin
Erica L. Larson
Biological invasions, Lidar, Meta-analysis, Restoration ecology, Salix, Tamarix
Control of invasive Tamarix spp. in riparian systems has long been a priority for management in western North America, but questions remain regarding the response of the broader plant community to different treatments. Here we summarize a series of approaches at different scales to quantify the effects of Tamarix control on characteristics of this ecosystem, including provisioning of wildlife habitat. In the first chapter we analyzed findings of the last 20 years using meta-analysis and found that although treatment has been successful in reducing Tamarix and promoting native vegetation to some extent, most literature reports very small effect sizes and there are still knowledge gaps. Specifically, questions remain around whether the tree/shrub species and/or functional groups that replace Tamarix following treatment can provide adequate bird habitat. Thus, in the second chapter we quantified the effect of Tamarix control on recovery of Salix (willow) spp.; species in this genus have a similar biomass distribution to Tamarix, which allows them each to provide habitat for cup-nesting birds of special interest. We found that (1) while a decrease in Tamarix is associated with an increase in Salix under some treatment and environmental conditions, Salix did not fully replace Tamarix as a dominant woody species, and (2) while treatment methods were overall not strong predictors of Salix regrowth, application of herbicide to invasive vegetation was associated with increased positive change in Salix cover. To investigate broader-scale dynamics around bird habitat provisioning in this system, in the third chapter we sought to determine whether morphology of the entire overstory is affected by treatment actions and environmental characteristics using lidar data. We found that active reintroduction of native trees is associated with higher density of biomass after sufficient time for secondary succession, thus likely to provide superior habitat than other restoration approaches. Our results provide insight into post-restoration trajectories of a novel ecosystem and show that it is possible, albeit difficult, to promote wildlife conservation through planned management of invasive vegetation.
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Alexander R. B. Goetz
Received from ProQuest
Goetz, Alexander R. B., "Plant Community Response to Control of a Dominant Invader at Multiple Scales" (2023). Electronic Theses and Dissertations. 2243.
Available for download on Friday, August 01, 2025