Matching Items (3)
Description
Biological soil crusts (biocrust) are photosynthetic communities of organisms forming in the top millimeters of unvegetated soil. Because soil crusts contribute several ecosystem services to the areas they inhabit, their loss under anthropogenic pressure has negative ecological consequences. There is a considerable interest in developing technologies for biocrust restoration such as biocrust nurseries to grow viable inoculum and the optimization of techniques for field deployment of this inoculum. For the latter, knowledge of the natural rates of biocrust dispersal is needed. Lateral dispersal can be based on self-propelled motility by component microbes, or on passive transport through propagule entrainment in runoff water or wind currents, all of which remain to be assessed. I focused my research on determining the capacity of biocrust for lateral self-propelled dispersal. Over the course of one year, I set up two greenhouse experiments where sterile soil substrates were inoculated with biocrusts and where the lateral advancement of biocrust and their cyanobacteria was monitored using time-course photography, discrete determination of soil chlorophyll a concentration, and microscopic observations. Appropriate uninoculated controls were also set up and monitored. These experiments confirm that cyanobacterial biological soil crusts are capable of laterally expanding when provided with presumably optimal watering regime similar to field conditions and moderate temperatures. The maximum temperatures of Sonoran Desert summer (up to 42 °C), exacerbated in the greenhouse setting (48 °C), caused a loss of biomass and the cessation of lateral dispersal, which resumed as temperature decreased. In 8 independent experiments, biocrust communities advanced laterally at an average rate of 2 cm per month, which is half the maximal rate possible based on the instantaneous speed of gliding motility of the cyanobacterium Microcoleus vaginatus. In a span of three months, populations of M. vaginatus, M. steenstrupii, and Scytonema spp. advanced 1 cm/month on average. The advancing crust front was found to be preferentially composed of hormogonia (differentiated, fast-gliding propagules of cyanobacteria). Having established the potential for laterally self-propelled community dispersal (without wind or runoff contributions) will help inform restoration efforts by proposing minimal inoculum size and optimal distance between inoculum patches.
ContributorsSorochkina, Kira (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Rowe, Helen (Committee member) / Wu, Jianguo (Committee member) / Arizona State University (Publisher)
Created2017
Description
For more than 100 years, the Unite States National Park Service (NPS) has been guided by a mandate to preserve parks and their resources for the enjoyment of present and future generations. But all parks are subject to conditions that may frustrate preservation efforts. Climate change is melting the glaciers. Rising seas are sweeping away protected shorelines. Development projects, accompanied by air, water, light, and noise pollution, edge closer to parks and fragment habitats. The number of visitors and vested interests are swelling and diversifying. Resources for preservation, such as funds and staff, seem to be continuously shrinking, at least relative to demand.
Still, the NPS remains committed to the preservation of our natural and cultural heritage. Yet the practice of that promise is evolving, slowly and iteratively, but detectably. Through explorations of legal and scholarly literature, as well as interviews across the government, non-profit, and academic sectors, I’ve tracked the evolution of preservation in parks. How is preservation shifting to address socio-ecological change? How has preservation evolved before? How should the NPS preserve parks moving forward?
The practice of preservation has come to rely on science, including partnerships with academic researchers, as well as inventory and monitoring programs. That shift has in part been guided by goals that have also become more informed by science, like ecological integrity. While some interviewees see science as a solution to the NPS’s challenges, others wonder how applying science can get “gnarly,” due to uncertainty, lack of clear policies, and the diversity of parks and resources. “Gnarly” questions stem in part from the complexity of the NPS as a socio-ecological system, as well as from disputed, normative concepts that underpin the broader philosophy of preservation, including naturalness. What’s natural in the context of pervasive anthropogenic change? Further, I describe how parks hold deep, sometimes conflicting, cultural and symbolic significance for their local and historical communities and for our nation. Understanding and considering those values is part of the gnarly task park managers face in their mission to preserve parks. I explain why this type of conceptual and values-based uncertainty cannot be reduced through science.
Still, the NPS remains committed to the preservation of our natural and cultural heritage. Yet the practice of that promise is evolving, slowly and iteratively, but detectably. Through explorations of legal and scholarly literature, as well as interviews across the government, non-profit, and academic sectors, I’ve tracked the evolution of preservation in parks. How is preservation shifting to address socio-ecological change? How has preservation evolved before? How should the NPS preserve parks moving forward?
The practice of preservation has come to rely on science, including partnerships with academic researchers, as well as inventory and monitoring programs. That shift has in part been guided by goals that have also become more informed by science, like ecological integrity. While some interviewees see science as a solution to the NPS’s challenges, others wonder how applying science can get “gnarly,” due to uncertainty, lack of clear policies, and the diversity of parks and resources. “Gnarly” questions stem in part from the complexity of the NPS as a socio-ecological system, as well as from disputed, normative concepts that underpin the broader philosophy of preservation, including naturalness. What’s natural in the context of pervasive anthropogenic change? Further, I describe how parks hold deep, sometimes conflicting, cultural and symbolic significance for their local and historical communities and for our nation. Understanding and considering those values is part of the gnarly task park managers face in their mission to preserve parks. I explain why this type of conceptual and values-based uncertainty cannot be reduced through science.
ContributorsSullivan Govani, Michelle (Author) / Minteer, Ben A (Thesis advisor) / Budruk, Megha (Committee member) / Sarewitz, Daniel (Committee member) / Theuer, Jason (Committee member) / Arizona State University (Publisher)
Created2019
Description
The issue of wild horse management in the American West has become prevalent in the media recently and management strategies are often criticized and opposed by the public. Horses have been a core feature of American history and culture nearly since the colonization of the western frontier, and popular media such as television and movies paint a romantic but often unrealistic picture of wild horses. Land management agencies must balance limited resources with an ever-growing wild horse population in order to properly manage public land so that it retains its ecological integrity and is still able to be used by multiple stakeholders, and they also must endure public criticism throughout the process. I used a photo elicitation survey to gather responses to photographic images of wild horses and determine how the public feels about wild horse management, given that horses are seen as a symbol of freedom and the American West. It was revealed that people who are unfamiliar with the issue still have opinions about how the horses should be managed, and these opinions often mirror what can be found in popular media.
ContributorsDuran, Kiana Alexis (Author) / Minteer, Ben (Thesis director) / Schoon, Michael (Thesis director) / Murphree, Julie (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05