Matching Items (9)
Description
Growth of the Phoenix metropolitan area led to exposures of the internal bedrock structure of surrounding semi-arid mountain ranges as housing platforms or road cuts. Such exposures in the Sonoran and Mojave deserts reveal the presence of sedimentary calcium carbonate infilling the pre-existing fracture matrix of the bedrock. Field surveys of bedrock fractures filled with carbonate (BFFC) reveal an average of 0.079 +/- 0.024 mT C/m2 stored in the upper 2 m of analyzed bedrock exposures. Back-scattered electron microscopy images indicate the presence of carbonate at the micron scale, not included in this estimation. Analysis of the spatial extent of bedrock landforms in arid and semi-arid regions worldwide suggests that ~1485 GtC could potentially be stored in the upper 2 m horizon of BFFCs. Radiocarbon dating obtained at one of the sites indicates it is likely that some of the carbonate was flushed into the bedrock system during glacial wet pulses, and is stored on Pleistocene timescales or longer. Strontium isotope analysis at the same site suggest the potential for a substantial cation contribution from weathering of the local bedrock, indicating the potential exists for sequestration of atmospheric carbon in BFFCs. Rates of carbon release from BFFCs are tied to rates of erosion of bedrock ranges in desert climates.
ContributorsHarrison, Emma (Author) / Dorn, Ronald (Thesis advisor) / Reynolds, Stephen (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2013
Description
Ephemeral streams in Arizona that are perpendicularly intersected by the Central Arizona Project (CAP) canal have been altered due to partial or complete damming of the stream channel. The dammed upstream channels have experienced decades long cycles of sediment deposition and waterlogging during storm events causing the development of "green-up" zones. This dissertation examines the biogeomorphological effects of damming ephemeral streams caused by the CAP canal by investigating: (1) changes in the preexisting spatial cover of riparian vegetation and how these changes are affected by stream geometry; (2) green-up initiation and evolution; and (3) changes in plant species and community level changes. To the author's knowledge, this is the only study that undertakes an interdisciplinary approach to understanding the environmental responses to anthropogenically-altered ephemeral stream channels. The results presented herein show that vegetation along the upstream section increased by an average of 200,872 m2 per kilometer of the CAP canal over a 28 year period. Vegetation growth was compared to channel widths which share a quasi-linear relationship. Remote sensing analysis of Landsat TM images using an object-oriented approach shows that riparian vegetation cover gradually increased over 28 years. Field studies reveal that the increases in vegetation are attributed to the artificial rise in local base-level upstream created by the canal, which causes water to spill laterally onto the desert floor. Vegetation within the green-up zone varies considerably in comparison to pre-canal construction. Changes are most notable in vegetation community shifts and abundance. The wettest section of the green-up zone contains the greatest density of woody plant stems, the greatest vegetation volume, and a high percentage of herbaceous cover. Vegetation within wetter zones changed from a tree-shrub to a predominantly tree-herb assemblage, whereas desert shrubs located in zones with intermediate moisture have developed larger stems. Results from this study lend valuable insight to green-up processes associated with damming ephemeral streams, which can be applied to planning future canal or dam projects in drylands. Also, understanding the development of the green-up zones provide awareness to potentially avoiding flood damage to infrastructure that may be unknowingly constructed within the slow-growing green-up zone.
ContributorsHamdan, Abeer (Author) / Schmeeckle, Mark (Thesis advisor) / Myint, Soe (Thesis advisor) / Dorn, Ronald (Committee member) / Stromberg, Juliet (Committee member) / Arizona State University (Publisher)
Created2014
Description
This work investigates the effects of non-random sampling on our understanding of species distributions and their niches. In its most general form, bias is systematic error that can obscure interpretation of analytical results by skewing samples away from the average condition of the system they represent. Here I use species distribution modelling (SDM), virtual species, and multiscale geographically weighted regression (MGWR) to explore how sampling bias can alter our perception of broad patterns of biodiversity by distorting spatial predictions of habitat, a key characteristic in biogeographic studies. I use three separate case studies to explore: 1) How methods to account for sampling bias in species distribution modeling may alter estimates of species distributions and species-environment relationships, 2) How accounting for sampling bias in fossil data may change our understanding of paleo-distributions and interpretation of niche stability through time (i.e. niche conservation), and 3) How a novel use of MGWR can account for environmental sampling bias to reveal landscape patterns of local niche differences among proximal, but non-overlapping sister taxa. Broadly, my work shows that sampling bias present in commonly used federated global biodiversity observations is more than enough to degrade model performance of spatial predictions and niche characteristics. Measures commonly used to account for this bias can negate much loss, but only in certain conditions, and did not improve the ability to correctly identify explanatory variables or recreate species-environment relationships. Paleo-distributions calibrated on biased fossil records were improved with the use of a novel method to directly estimate the biased sampling distribution, which can be generalized to finer time slices for further paleontological studies. Finally, I show how a novel coupling of SDM and MGWR can illuminate local differences in niche separation that more closely match landscape genotypic variability in the two North American desert tortoise species than does their current taxonomic delineation.
ContributorsInman, Richard (Author) / Franklin, Janet (Thesis advisor) / Fotheringham, A. Stewart (Committee member) / Dorn, Ronald (Committee member) / Arizona State University (Publisher)
Created2018
Description
In this project, I examined the relationship between lockdowns implemented by COVID-19 and the activity of animals in urban areas. I hypothesized that animals became more active in urban areas during COVID-19 quarantine than they were before and I wanted to see if my hypothesis could be researched through Twitter crowdsourcing. I began by collecting tweets using python code, but upon examining all data output from code-based searches, I concluded that it is quicker and more efficient to use the advanced search on Twitter website. Based on my research, I can neither confirm nor deny if the appearance of wild animals is due to the COVID-19 lockdowns. However, I was able to discover a correlational relationship between these two factors in some research cases. Although my findings are mixed with regard to my original hypothesis, the impact that this phenomenon had on society cannot be denied.
ContributorsHeimlich, Kiana Raye (Author) / Dorn, Ronald (Thesis director) / Martin, Roberta (Committee member) / Donovan, Mary (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Physical and structural tree measurements are applied in forestry, precision agriculture and conservation for various reasons. Since measuring tree properties manually is tedious, measurements from only a small subset of trees present in a forest, agricultural land or survey site are often used. Utilizing robotics to autonomously estimate physical tree dimensions would speed up the measurement or data collection process and allow for a much larger set of trees to be used in studies. In turn, this would allow studies to make more generalizable inferences about areas with trees. To this end, this thesis focuses on developing a system that generates a semantic representation of the topology of a tree in real-time. The first part describes a simulation environment and a real-world sensor suite to develop and test the tree mapping pipeline proposed in this thesis. The second part presents details of the proposed tree mapping pipeline. Stage one of the mapping pipeline utilizes a deep learning network to detect woody and cylindrical portions of a tree like trunks and branches based on popular semantic segmentation networks. Stage two of the pipeline proposes an algorithm to separate the detected portions of a tree into individual trunk and branch segments. The third stage implements an optimization algorithm to represent each segment parametrically as a cylinder. The fourth stage formulates a multi-sensor factor graph to incrementally integrate and optimize the semantic tree map while also fusing two forms of odometry. Finally, results from all the stages of the tree mapping pipeline using simulation and real-world data are presented. With these implementations, this thesis provides an end-to-end system to estimate tree topology through semantic representations for forestry and precision agriculture applications.
ContributorsVishwanatha, Rakshith (Author) / Das, Jnaneshwar (Thesis advisor) / Martin, Roberta (Committee member) / Throop, Heather (Committee member) / Zhang, Wenlong (Committee member) / Ehsani, Reza (Committee member) / Arizona State University (Publisher)
Created2022
Description
A novel underwater, open source, and configurable vehicle that mimics and leverages advances in quad-copter controls and dynamics, called the uDrone, was designed, built and tested. This vehicle was developed to aid coral reef researchers in collecting underwater spectroscopic data for the purpose of monitoring coral reef health. It is designed with an on-board integrated sensor system to support both automated navigation in close proximity to reefs and environmental observation. Additionally, the vehicle can serve as a testbed for future research in the realm of programming for autonomous underwater navigation and data collection, given the open-source simulation and software environment in which it was developed. This thesis presents the motivation for and design components of the new vehicle, a model governing vehicle dynamics, and the results of two proof-of-concept simulation for automated control.
ContributorsGoldman, Alex (Author) / Das, Jnaneshwar (Thesis advisor) / Asner, Greg (Committee member) / Marvi, Hamidreza (Committee member) / Arizona State University (Publisher)
Created2020
Description
Coastal dunes are dynamic landforms that provide the first defense for sea-level rise and coastal flooding. Coastal dunes depend on vegetation to trap and store sediment, which alters beach-dune sediment budgets and foredune morphology. Invasive vegetation species change these patterns and alter how the system responds to both littoral and aeolian processes. Dynamic restoration is a growing practice whereby plant communities are modified to enhance aeolian processes and help return coastal dune ecosystems to a more ‘natural’ state of ecosystem structure and function. A portion of the foredune system at the Lanphere Dunes in the Humboldt Bay National Wildlife Refuge (HBNWR), near Arcata in northern California was targeted for dynamic restoration. The invasive plant species Ammophila arenaria (European beach grass) was removed in August 2015, while native vegetation treatments consisting of combinations of a dune mat forb assemblage and the dune grass Elymus mollis (Sea Lyme-grass) were planted over the summer and over the winter of 2016-17. Four different vegetation regimes were studied consisting of a control plot of A. arenaria two plots of exclusively Dune mat and E. mollis, and then a plot that is the combination if Dune mat and E. mollis. This restoration presented the opportunity to study the patterns of vegetation re-establishment and the related responses in sedimentation and morphological adjustment of the foredune system at both the landform and vegetation plot scales. Bi-annual terrestrial laser scanning surveys and cross-shore transects were used to calculate volumes of sediment change, distinguish patterns of sediment erosion/deposition and discern geomorphic change within different plant cover types. Results suggest that the Dune mat-E. mollis assemblage was most effective a trapping sediment with 96.9% of the plot experiencing deposition over the 17-month observation period, to a spatially averaged depth of +0.16m. During the study, the Dune mat treatment site experienced a landward flattening of its crest and considerable erosion of up to -0.5m around the plants, resulting in a normalized volumetric change of -0.139 m3 m-2. The E. mollis site experienced considerable sediment bypassing on the stoss slope and deposition on the lee slope of the foredune, resulting in accumulation at the toe of the lee slope of +0.6m while base of the lee slope moved 4m landwards. Site morphodynamics and sediment budgets were also influenced by changes in vegetation density and recovery from storm erosion. Longer terms studies could be conducted to investigate responses to vegetation disturbances over a longer temporal scale.
ContributorsHuck, Rosemary Alice (Author) / Walker, Ian (Thesis director) / Dorn, Ronald (Committee member) / Historical, Philosophical & Religious Studies (Contributor) / School of Geographical Sciences and Urban Planning (Contributor, Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The scientific research conducted by science, technology, engineering, and mathematics (STEM) institutions is groundbreaking. Everyday, scientists create a deeper understanding of the world around us, and then communicate that understanding through journal papers, articles, and conferences. To strengthen these traditional forms of communication, science communicators can use social media platforms such as Twitter and Facebook to promote themselves and earn digital audience engagement that will grow the impact and success of their research. This thesis synthesizes research on human communication theories, digital user behavior, and science communication practices in order to create the “Science Communicator’s Guide to Social Media Engagement”. This guide empowers science communicators to utilize social media in a way that can increase their digital audience engagement, expand the reach of their research, and ultimately amplify their professional presence in the scientific community.
ContributorsVandekop, Victoria Margueritte (Author) / Asner, Greg (Thesis director) / Martin, Roberta (Committee member) / Hugh Downs School of Human Communication (Contributor) / Watts College of Public Service & Community Solut (Contributor) / Barrett, The Honors College (Contributor)
Created2020-12
Description
Major challenges in geography education have existed and continue to exist today. Through three significant challenges, this dissertation examines how geography pedagogy can be changed to help fight university geography enrollment declines. The first challenge analyzes an introductory geography course and the motivational impact of gamifying the class grading scale. In particular, this research examines student responses to questions related to a point-accrual approach. The second challenge looks to K-12 teachers who teach geography but have no official university geography training. This research strategy is two-fold: first, surveys taken by participants and their individual developed lessons in the 2018, 2019, and 2022 Alliance Summer Geography Institutes (ASGIs) were analyzed; second, pathways of out-of-field retired teacher consultants (TCs) who have gone on to teach “social studies methods” courses in Arizona’s colleges of education were examined. The third and final challenge investigates the use of a K-12 educational website before, during, and after the COVID-19 pandemic lockdowns. The study focuses on the Arizona Geographic Alliance resource heavy website which provides lesson plans, maps, activity books, and more to educators around the globe. Two research questions incorporated into this section of the dissertation are: (i) generally, how did the COVID-19 pandemic impact use of the Arizona Geographic Alliance website? and more specifically, (ii) could the analysis of the website usage be used to help the recruitment of new college geography students by providing K-12 teachers appropriate resources about geography as a career? The results of this research identify and address weak links facing the future of geography education, with the hope that encourages education intervention to increase the number of interested geography students and inspires further geography education research to continue developing solutions to these and other ongoing challenges.
ContributorsMoll, Heather L (Author) / Dorn, Ronald (Thesis advisor) / Villa Cerveny, Niccole (Committee member) / Rosales Chavez, Jose-Benito (Committee member) / Arizona State University (Publisher)
Created2024