Matching Items (4)
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- All Subjects: Conservation Biology
- All Subjects: Interannual variability
- Creators: Hall, Sharon
Description
The mainstream American environmental movement has a reputation for being ethnically homogenous (i.e., white), especially within the field of conservation. Low minority involvement has been noted and discussed in the conservation literature and within environmental organizations, but these discussions aren't always informed by the explicit social justice concerns critical to understanding the complex intersection of environmental and social issues. Communities of color have expressed concern for environmental and conservation issues, but often frame those issues in a different way than is common in mainstream conservation science, a framing that we can appreciate through a deeper analysis of the values and goals of the environmental justice (EJ) movement. A more thorough inclusion of EJ principles could be an effective method to increase ethnic diversity in the field of conservation, particularly within higher education conservation programs like the Conservation Biology and Ecology (CBE) concentration at Arizona State University. This thesis frames the broader challenge of diversity in conservation, the history and current state of the conservation movement, and the history of the environmental justice movement via a literature review. I then evaluate the university's CBE program on the basis of its diversity through an analysis of demographic data on undergraduate ethnicity from the School of Life Sciences. I conclude with a series of recommendations for enhancing the diversity of ASU's CBE program moving forward.
ContributorsLiska, Kelly Margaret (Author) / Minteer, Ben (Thesis director) / Richter, Jennifer (Committee member) / Hall, Sharon (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Jaguar population decline is largely attributed to habitat loss and retaliatory hunting. Maintaining a viable prey base in the wild can help to mitigate this issue and decrease human-wildlife conflicts. This study aims to assess the presence of prey species in jaguar habitat in order to inform conservation efforts to maintain and improve the health and relative abundance of the wildlife community. We analyzed nearly 40,000 photographs from 85 camera traps to assess the presence of prey species at sites where jaguars are known to occur. Jaguar-prey site overlap was calculated based on the percent of jaguar sites where each prey species was present. Medium-sized mammal prey species (e.g. Central American agouti) were present across the majority (up to 87%) of sites, while large mammal prey species were present in 16%-42% of sites, varying by species. These results suggest that conservation management of jaguars would benefit from improved monitoring and maintenance of a stable prey community.
ContributorsLewis-Quan, Kaidence (Author) / Schipper, Jan (Thesis director) / Hall, Sharon (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Geographical Sciences and Urban Planning (Contributor)
Created2023-05
Description
It’s no secret that wetlands have dramatically declined in the arid and semiarid American West, yet the small number of wetlands that persist provide vital ecosystem services. Ciénega is a term that refers to a freshwater arid-land wetland. Today, even in areas where ciénegas are prominent they occupy less than 0.1% of the landscape. This investigation assesses the distribution of vascular plant species within and among ciénegas and address linkages between environmental factors and wetland plant communities. Specifically, I ask: 1) What is the range of variability among ciénegas, with respect to wetland area, soil organic matter, plant species richness, and species composition? 2) How is plant species richness influenced locally by soil moisture, soil salinity, and canopy cover, and regionally by elevation, flow gradient (percent slope), and temporally by season? And 3) Within ciénegas, how do soil moisture, soil salinity, and canopy cover influence plant species community composition? To answer these questions I measured environmental variables and quantified vegetation at six cienegas within the Santa Cruz Watershed in southern Arizona over one spring and two post-monsoon periods. Ciénegas are highly variable with respect to wetland area, soil organic matter, plant species richness, and species composition. Therefore, it is important to conserve the ciénega landscape as opposed to conserving a single ciénega. Plant species richness is influenced negatively by soil moisture, positively by soil salinity, elevation, and flow gradient (percent slope), and is greater during the post-monsoon season. Despite concerns about woody plant encroachment reducing biodiversity, my investigation suggests canopy cover has no significant influence on ciénega species richness. Plant species community composition is structured by water availability at all ciénegas, which is consistent with the key role water availability plays in arid and semiarid regions. Effects of canopy and salinity structuring community composition are site specific. My investigation has laid the groundwork for ciénega conservation by providing baseline information of the ecology of these unique and threatened systems. The high variability of ciénega wetlands and the rare species they harbor combined with the numerous threats against them and their isolated occurrences makes these vanishing communities high priority for conservation.
ContributorsWolkis, Dustin (Author) / Stromberg, Juliet C. (Thesis advisor) / Hall, Sharon (Committee member) / Salywon, Andrew (Committee member) / Makings, Elizabeth (Committee member) / Arizona State University (Publisher)
Created2016
Description
Climate change will result not only in changes in the mean state of climate but also on changes in variability. However, most studies of the impact of climate change on ecosystems have focused on the effect of changes in the central tendency. The broadest objective of this thesis was to assess the effects of increased interannual precipitation variation on ecosystem functioning in grasslands. In order to address this objective, I used a combination of field experimentation and data synthesis. Precipitation manipulations on the field experiments were carried out using an automated rainfall manipulation system developed as part of this dissertation. Aboveground net primary production responses were monitored during five years. Increased precipitation coefficient of variation decreased primary production regardless of the effect of precipitation amount. Perennial-grass productivity significantly decreased while shrub productivity increased as a result of enhanced precipitation variance. Most interesting is that the effect of precipitation variability increased through time highlighting the existence of temporal lags in ecosystem response.
Further, I investigated the effect of precipitation variation on functional diversity on the same experiment and found a positive response of diversity to increased interannual precipitation variance. Functional evenness showed a similar response resulting from large changes in plant-functional type relative abundance including decreased grass and increased shrub cover while functional richness showed non-significant response. Increased functional diversity ameliorated the direct negative effects of precipitation variation on ecosystem ANPP but did not control ecosystem stability where indirect effects through the dominant plant-functional type determined ecosystem stability.
Analyses of 80 long-term data sets, where I aggregated annual productivity and precipitation data into five-year temporal windows, showed that precipitation variance had a significant effect on aboveground net primary production that is modulated by mean precipitation. Productivity increased with precipitation variation at sites where mean annual precipitation is less than 339 mm but decreased at sites where precipitation is higher than 339 mm. Mechanisms proposed to explain patterns include: differential ANPP response to precipitation among sites, contrasting legacy effects and soil water distribution.
Finally, increased precipitation variance may impact global grasslands affecting plant-functional types in different ways that may lead to state changes, increased erosion and decreased stability that can in turn limit the services provided by these valuable ecosystems.
Further, I investigated the effect of precipitation variation on functional diversity on the same experiment and found a positive response of diversity to increased interannual precipitation variance. Functional evenness showed a similar response resulting from large changes in plant-functional type relative abundance including decreased grass and increased shrub cover while functional richness showed non-significant response. Increased functional diversity ameliorated the direct negative effects of precipitation variation on ecosystem ANPP but did not control ecosystem stability where indirect effects through the dominant plant-functional type determined ecosystem stability.
Analyses of 80 long-term data sets, where I aggregated annual productivity and precipitation data into five-year temporal windows, showed that precipitation variance had a significant effect on aboveground net primary production that is modulated by mean precipitation. Productivity increased with precipitation variation at sites where mean annual precipitation is less than 339 mm but decreased at sites where precipitation is higher than 339 mm. Mechanisms proposed to explain patterns include: differential ANPP response to precipitation among sites, contrasting legacy effects and soil water distribution.
Finally, increased precipitation variance may impact global grasslands affecting plant-functional types in different ways that may lead to state changes, increased erosion and decreased stability that can in turn limit the services provided by these valuable ecosystems.
ContributorsGherardi Arbizu, Laureano (Author) / Sala, Osvaldo E. (Thesis advisor) / Childers, Daniel (Committee member) / Grimm, Nancy (Committee member) / Hall, Sharon (Committee member) / Wu, Jingle (Committee member) / Arizona State University (Publisher)
Created2014