136879 research outputs found
Sort by
Soil and Bedrock Hydraulic Properties and Water Dynamics in a Semiarid Karst Region Undergoing Woody Plant Encroachment
No full textWater-limited ecosystems, encompassing approximately 40% of the Earth's surface, are undergoing transformative changes due to human activities, impacting their water cycles significantly. A pivotal transformation in these drylands is the phenomenon of woody plant encroachment (WPE), where landscapes historically dominated by herbaceous vegetation witness increased shrub and tree cover. This dissertation investigates the multifaceted implications of WPE in the soil and bedrock water dynamics of semiarid karst landscapes, focusing on the Edwards Plateau region of central Texas.
In chapter two, we systematically evaluated the effects of an encroaching shrub, Redberry juniper, on soil infiltrability. We found that infiltrability beneath shrubs quintupled, and percolation depth nearly tripled compared to intercanopy zones. Remarkably, we found that the even small saplings already had a major impact on soil properties. Our results shed light on the potential role of WPE, especially juniper invasion, in promoting baseflows and groundwater recharge by improving soil infiltrability.
Chapter three explores the effects of WPE on the hydraulic properties of bedrock substrates. Our field study in the Edwards Plateau examined bedrock, comparing a site heavily encroached by woody plants (mainly Live oak and Ashe juniper) with another where woody plants have been suppressed for the past 80 years. The findings reveal that the woody-plant-encroached site exhibited a tenfold increase in the mean saturated hydraulic conductivity of the bedrock. Furthermore, encroachment was associated with greater limestone matrix porosity and an accelerated weathering rate of the bedrock. These findings underline the potential of WPE to drastically modify the permeability of shallow bedrock within a few decades.
In chapter four we highlight the importance of monitoring rock moisture in the vadose zone, an often-overlooked component of the terrestrial hydrological cycle, especially in areas with shallow soils. Our research evaluated a commercial soil moisture sensor's efficacy in continuously monitoring weathered limestone's water content. Results indicate that rock moisture measurements are feasible and reliable with the sensors, provided specific installation and calibration protocols are followed. Data showed that limestone stored substantial water amounts, which was mostly utilized during dry periods.
In chapter five we monitored soil and rock water storage dynamics at two sites representing the main geological formations of the western portion of the Edwards Plateau. Our study provides evidence for the effect of woody plants in increasing the storage capacity of bedrock. We also show that storage dynamics are influenced by the underlying geology and differ substantially across different hillslope positions. Finally, we show evidence for the importance of rock moisture for plant transpiration, particularly during extended droughts when soil moisture is depleted.
Altogether, our findings illustrate how WPE intricately affects the hydrological connectivity of landscapes in the Edwards Plateau. By enhancing soil infiltrability and bedrock permeability, WPE can accelerate vertical water flows. However, the ecohydrological implications of this phenomenon are nuanced. In some areas, these changes might lead to higher recharge, especially during extended wet periods. However, on many upland locations and during dry years, there is limited potential for direct groundwater recharge and most water stored within the soils and bedrock is eventually transpired. In such cases, the implications of improved infiltration and storage are mainly ecological and can help explain the success of woody plants such as junipers and oaks at encroaching in the Edwards Plateau
Grain Variety Picks for Texas High Plains 2023-2024 Wheat Year & 2022-2023 Texas High Plains Wheat Production Summary
Get PDFDryland Conservation Tillage for the Southern Great Plains
No full textDryland Conservation Tillage for the Southern Great Plain
Microbial Communities in the Phyllosphere of Spinach Grown in Soil With Different Nitrogen Contents and Their Role in the Colonization by Foodborne Pathogens
No full textSeveral spinach-related outbreaks of foodborne illness occur every year. Spinach leaves are inhabited by a variety of microorganisms, some of which may have antagonistic activity against foodborne pathogens if present. The present study aims to investigate changes in the bacterial community composition in the phyllosphere of spinach plants grown in soil with different nitrogen content and to determine the antagonistic activity of spinach isolates against foodborne pathogens.
Sixty-eight spinach samples were processed using culture-dependent and culture-independent methods to evaluate the bacterial community composition in the phyllosphere of spinach and to search for spinach native microbiota with potential antagonistic activity. In culture-dependent methods, populations of mesophiles (MS), psychrotrophs (PY) coliforms (CL) and lactic acid bacteria (LAB) were quantified by plate counts using adequate culture media. In culture-independent methods, the bacterial diversity from the phyllosphere was determined by amplicon sequencing based on the V3-V4 region of the bacterial 16S rRNA gene. From each of the different types of microbiological media used in the culture-dependent assay, colonies were isolated and screened for antagonistic activity toward Shiga-toxin-producing E. coli (STEC), Salmonella enterica, and Listeria monocytogenes. Five of the antagonistic isolates were then selected to determine if the inhibitory activity observed in vitro could be replicated on spinach leaves.
Counts of MS, PY, LAB, and CL on low-nitrogen soil-grown spinach were 6.9, 7.1, 5.5, and 7.4 log CFU/g, respectively, while high-nitrogen soil-grown spinach showed counts of 7.0, 7.0, 5.7, and 7.5 log CFU/g, with no significant difference (p > 0.05). Amplicon sequencing, however, revealed differences in relative abundance between different taxa levels in relation to soil nitrogen levels.
A total of 1,550 isolates were randomly selected from the microbial groups tested. From these, 122 isolates presented antagonism against at least one pathogen, with 63% identified up to the genus level. Lactococcus was the most frequently identified genus followed by Enterococcus and Bacillus, while Exiguobacterium, Paenarthrobacter, and Staphylococcus had fewer representatives. The number of antagonistic isolates recovered from soils with high and low nitrogen levels did not differ significantly.
Despite in vitro antagonism against all three pathogens by L. lactis, B. thuringiensis, E. mundtii, E. acetylicum, and Staphylococcus sp., their inhibitory activity could not be replicated on spinach leaves. None of these organisms reduced STEC and S. enterica growth significantly, whereas B. thuringiensis and E. acetylicum, reduced the growth of L. monocytogenes. However, the spent media of all the isolates was able to inhibit the growth of the three pathogens, suggesting that the production of secondary is responsible for the observed inhibition.
The results from this study suggest that some spinach epiphytic bacteria can be used as potential biocontrol agents against some bacterial pathogens. Further research will support best practices for the effective use of these antagonistic bacteria
Dynamic Graph Visualization Techniques
Get PDFGraphs are amongst the most important and common data structures found throughout the field of computer science. Thoroughly understanding graph operations and algorithms is crucial for students in the discipline. Unfortunately, graph algorithms can be very challenging to follow by hand, and this can be attributed to their abstract nature, long subroutines, and many variables to keep track of. Although it is common for students in university algorithm courses to code graph algorithms using some high-level programming language, students are only able to see their program���s output rather than the steps the program took to produce it. On top of that, a graph���s topology can greatly influence the behavior of an algorithm. Instructors may choose to trace an algorithm���s steps within a lecture, but their examples are usually limited by the aforementioned difficulties. Like instructors, researchers in the field of graph theory often necessitate a way of illustrating dynamic processes on graphs. These types of visualizations are useful when presenting research work and new algorithms to audiences in academic conferences and forums. The goal of this project is to create a tool that can assist students in analyzing the behavior of common graph algorithms through interactive visualizations, and also provide instructors and researchers the ability to create, load, and save dynamic graphs and visualizations that could then be incorporated in lectures or research presentations
Understanding the Role of Existential Threats and Social Attachments in Climate Change and Natural Hazard Threat Evaluation and Action
Get PDFDuring extreme weather events, individuals utilize information from government agencies, media sources, their social networks, and communities to analyze risks associated with impending natural hazards. This perception of risk is a key determinant in the course of action taken to mitigate the impacts of natural hazards. With global climate change continually increasing the severity and intensity of natural hazards and extreme weather events, how we effectively communicate information about the impacts of climate change and natural hazards is critical to protecting individuals and developing resilient communities. However, climate change is often communicated through scenarios of destruction, death, and lack of control. Two experimental studies on the Texas Gulf Coast and one cross-sectional study with a nationally representative sample sought to understand how characteristics of climate change and natural hazards communication and social attachment influence mitigation, adaptation, and preparedness intentions. Findings suggest that existential fear increases risk perceptions, especially in low- and medium-severity scenarios (study 1). Sense of community and perceptions of community adaptive capacity insulate individuals from the impacts of existential threats (study 2). Furthermore, research suggests that in-group norms may guide appropriate action. Results reveal that the strengths of partisan and ideological social identities are highly predictive of norm-neutralizing beliefs, which reduce personal norms to support climate action (Study 3). These findings collectively provide marginal support for TMT backfire outcomes in the natural hazard context and support the use of mortality salience in certain scenarios. Further, the results suggest that social identities and group norms are increasingly influential for climate action and should be explored further through norm-neutralization
