Browsing by Author "Melzer, Suellen, committee member"
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Item Open Access Assessing the salinity effects and economic feasibility of on-farm desalination technology in irrigated semi-arid regions(Colorado State University. Libraries, 2021) Barnes, Kaitlyn, author; Bailey, Ryan, advisor; Sharvelle, Sybil, committee member; Melzer, Suellen, committee memberHigh salinity levels in areas with intensive agricultural practices can inhibit agricultural productivity. Semi-arid regions where irrigation is used to support crop growth are particularly impacted by the quality of surface and groundwater sources. In this study, we use a combined numerical modeling and economic analysis approach to estimate the regional impact of an on-farm desalination technology on multi-decadal salinity fate and transport and explore whether the technology is viable to improve soil health, crop yield, and long-term profitability. A subsurface salt transport model (MODFLOW-RT3D) is applied to a 50,600-ha (125,000 acres) region in southeastern Colorado located within the Arkansas River Valley. The model simulates the reactive transport in soils and groundwater of 8 major salt ions (Ca+, Mg2+, Na+, K, SO42-, CO32-, HCO3-, and Cl-). Simulated values of average soil water concentration (TDS) are used to estimate crop relative yield with and without salt removal at various removal rates (Baseline – no salt removed; Unit removal – average of 60% salt removed; 100% salt removal) and time periods (5, 10, 15, 20, 25 years after desalination begins). The Unit removal rate is calibrated to align with a solar powered, reverse-osmosis desalination system that is currently being tested in semi-arid study area. For the Unit rate of 60% salt removal, the average TDS of the study area was found to decrease by an average of 20% over a period of 20 years, resulting in an increase in crop yield of 1.6 – 2.3%. Using data on regional production costs, crop prices, and the costs of building and operating the desalination system, we calculate the Net Present Value of production with the desalination unit. The results indicate that desalination does increase economic returns, particularly for high-valued specialty crops, such as melons and onions; however, these benefits are considerably less than the costs of operating the desalination technology.Item Open Access Deciphering the biological determinants on methane cycling from Gulf Coast wetlands(Colorado State University. Libraries, 2024) de Melo Ferreira, Djennyfer Karolaine, author; Wrighton, Kelly C., advisor; von Fischer, Joseph, committee member; Melzer, Suellen, committee member; Wilkins, Michael, committee memberIn Chapter 1, I introduce the importance of coastal wetlands for ecosystem services, including carbon storage, physical barrier for natural disasters, and habitat for diverse fauna and flora. Sea level rise is one of the main environmental risks affecting coastal wetlands, because of their geographic position. The effects of saltwater intrusion into freshwater wetlands can change established environmental conditions and vegetation coverage, which affects the functionality of various ecosystem functions they provide. These changes can also affect the methane emissions from coastal wetlands, which are major sources of this potent greenhouse gas. In this chapter, I evaluate the current knowledge of microbial methane production and consumption, including aspects of the ecophysiological adaptation to salinity, and the changes in the microbial ecological interactions modulated by increased salinity from marine water intrusion. In Chapter 2, I conducted a study to characterize the microbial communities and geochemistry of soil and water compartments in three coastal wetlands following a salinity gradient from Barataria Bay, Louisiana. To investigate the methane cycling microbial communities and their distribution on a freshwater flotant, Jean Lafitte swamp, and saltwater marsh wetlands, I collected soil and water samples under different vegetation coverage from each wetland. I analyzed the 16S rRNA gene sequencing and paired this data within situ methane fluxes and porewater concentrations. I also analyzed the geochemistry of the soil samples including profiling the anions, cations, pH, and redox conditions of soil and water samples across wetlands. The analysis showed that the diversity of methane cycling microbial communities decreased with increased salinity. Although the distribution and relative abundance of methanogen functional types was not impacted, with hydrogenotrophic methanogens being the most abundant across all wetlands. Looking at the methanotroph abundance and taxonomy in soil and water samples, I observed that swamp and saltwater wetlands share more methanotroph members in the water column, while the soils had more site-specific similarities. My research findings contribute to the understanding of methane cycling microbial tolerance to saltwater and may be used in future works to create more robust methane prediction models. In Chapter 3, I summarize the key aspects of microbial methane cycling in coastal wetlands and offer future directions for pairing geochemical and microbial data, including using an 'omics' approach and expanding investigation to more wetlands. We discuss the valuable findings these tools can give, contributing to a more accurate prediction of the metabolisms behind the ecophysiology and ecology of methane fluxes in coastal wetlands, and how targeting specific genes and metabolism can better help climate model efforts. In the Appendix sections, I give an expanded characterization of the wetlands site description, hydrology, vegetation and topological heterogeneity. I observed that, although relatively close in geographical position, each wetland has a different salinity range, vegetation type and microtopography that can influence the distribution of microorganisms in the soil and water. Here, we also analyzed the redox potential, dissolved oxygen, pH and geochemical compounds (bromide, nitrate, ammonium, acetate, sodium, potassium, magnesium, sulfate, chloride, and iron (II)) of these wetlands. We found no correlation between geochemistry with depth, but noticed higher salt contents in the saltwater marshes, and shared geochemistry between the swamp and freshwater flotant wetlands, as expected. Conclusively, this thesis contributes to the understanding of microbial communities to natural fluxes of methane in coastal wetlands and their interaction with the geochemistry of these ecosystems.Item Open Access Repurposing agricultural and municipal wastes to supply soil with plant-available phosphorus(Colorado State University. Libraries, 2019) Banet, Travis, author; Ippolito, Jim, advisor; Melzer, Suellen, committee member; Paschke, Mark, committee memberInorganic phosphorus (P) is a finite resource used to develop fertilizers, heavily applied in agricultural systems, necessary to maintain global crop yields that satisfy global food security needs. In addition to concerns regarding P availability in coming decades, aquatic ecosystems surrounding agricultural lands are susceptible to environmental degradation triggered by excessive P. We tested the ability of aluminum water treatment residuals (Al-WTR), which are known to efficiently sorb inorganic P, to remove organic P from livestock wastewater and subsequently return sorb P to solution. Results that showed Al-WTR can efficiently sorb organic P and desorb P to solution. A greenhouse study was conducted to validate the effectiveness of organic P laden Al-WTR (Al/O-WTR) for its ability to supply soil with plant-available P when compared to a liquid P amendment by growing spring wheat in two differently textured soils with low P concentrations. Results demonstrated that Al/O-WTR could comparably supply coarse textured soils with plant-available P; however, results showed that liquid P amendment is a superior source of plant-available P in fine textured soils.Item Open Access Soil seed bank composition and implications for ecological restoration in degraded Colorado shrublands(Colorado State University. Libraries, 2020) Schroeder, Ryan W. R., author; Paschke, Mark, advisor; Rhoades, Chuck, advisor; Meiman, Paul, committee member; Grant-Hoffman, M. Nikki, committee member; Melzer, Suellen, committee memberSoil seed banks of shrub-dominated ecosystems in western North America are poorly understood. The potential of the soil seed bank – the species composition and abundance of seeds – to impact ecological restoration has rarely been considered in ecological restoration of shrublands and could influence management decisions. I analyzed the germinable soil seed bank composition and distribution in two high-conservation priority ecosystems in Colorado. Studies were carried out to characterize seed bank composition and relationship to aboveground vegetation in "undesirable" and "desirable" plant communities; determine if "shrub islands" influence seed bank distribution; and assess the landscape and vertical distribution of the seed bank in a Bromus tectorum L. (cheatgrass) invaded rangeland. For all seed bank studies, soil seed bank samples were collected to a depth of 5 cm and grown in greenhouse conditions to determine the species composition and abundance of germinable seeds. I found that seed bank species richness and Shannon-Wiener diversity (H) did not differ in either shrubland between undesirable sites dominated by non-native vegetation and desirable sites dominated by native vegetation. Total seed abundance in a montane sagebrush shrubland was significantly greater in desirable sites (1401 ± 165 seeds m-2) compared to undesirable sites (588 ± 190 seed m-2). In a salt desert shrubland of the Colorado Plateau, total seed abundance did not differ, but on average non-native species seeds made up more than 60% of the total seed bank in undesirable sites, compared to 40% in desirable sites. In a separate study, shrub islands across Colorado were not associated with increased seed bank species richness or seed abundance compared to adjacent shrub-less interspaces. Differences in seed bank Shannon Wiener diversity (H) varied between shrublands, with salt desert shrublands having significantly greater (p-value < 0.05) seed bank diversity inside of shrub islands compared to shrub-less interspaces. Another study was conducted in a Bromus tectorum L. (cheatgrass) invaded rangeland of the Colorado Plateau to determine the seed bank horizontal and vertical distribution. The germinable soil seed bank had a greater abundance and lower spatial variability of native species seeds (3390 seeds m-2, CV = 75%) than non-native species seeds (1880 seeds m-2, CV: 124%) across the sampled landscape. Non-native species (primarily Bromus tectorum L.) seed were concentrated in the upper 2 cm soil (1294 ± 155, p-value <0.0001), but were found in substantive abundance in the 2 – 5 cm seed bank layer (585 ± 91). In addition to seed bank studies, in the fall of 2018, I established a study in a montane shrubland to test the effectiveness of seeding a high diversity native seed mix (39 species, 1496 PLS m-2) and treatments to increase site heterogeneity to increase native plant species diversity. One growing season following plot establishment, I found that plots that received a high diversity seed mix and those that received heterogeneity treatments had greater seeded species diversity (H) and richness than control plots.Item Open Access Weathering and soil properties on catenary sequences in forest and alpine ecosystems of the central Rocky Mountains(Colorado State University. Libraries, 2017) Bergstrom, Robert Mark, author; Kelly, Eugene F., advisor; Rhoades, Charles C., committee member; Borch, Thomas, committee member; Melzer, Suellen, committee member; Martin, Patrick H., committee memberThe evolution of soil landscapes can be evaluated by studying soil properties along catenary sequences—soil sequences that are hydrologically and topographically connected along hillslopes from higher elevation to lower elevation. Using the catena model, I investigated the manifestation of soil forming factors in conditioning weathering and soil development in the Mountain Ecosystems of the Fraser Experimental Forest (FEF), Colorado. The research outlined and presented in this dissertation is preceded by a short narrative on soil forming properties, hillslope models, and assessing weathering in soils. The work presented in this dissertation is a result of a multidisciplinary framework for pedological research, derived from the integration of and consideration of pedology, geomorphology, and hydrology. The future of pedological research will involve the assimilation of multidisciplinary approaches and thinking. This dissertation elucidates on (1) the distribution of soil properties along soil catenas and their implication for hydrologic and biogeochemical linkages across landscapes, (2) the evaluation of chemical alteration thru modeling soil strain along soil catenas, (3) the quantification and distribution of soil elemental fluxes along soil catenas, and (4) the determination of the contributions of weathering and atmospheric inputs to landscapes at FEF. My field sites were located in FEF, a model site of the alpine and forested environments of the central Rocky Mountains. The FEF is an ideal setting to study the interaction of soil forming factors in complex mountain terrain. A combination of traditional and more modern methods to explore the linkages between soil properties along mountain catenas were employed in order to gain insight into soil landscape evolution in complex mountain terrain. I established eight catenas along relatively steep mountain hillslopes while constraining the lithologic differences along the soil landscapes. Vegetative changes along these catenas could not be ignored; rather, the differences provided insight into the influence of vegetative cover on soil properties. Soils were sampled along the catenas, beginning in the mountaintop landscapes (crests or summit) and ending in the mountainbase landscapes, where wetlands along riparian corridors dominate. Soil morphology and soil chemistry along the catenas provided understanding into the evolution of soil landscapes at FEF and their connectedness to the hydrologic flowpaths along these hillslopes. Results suggested that these soil landscapes are in various states of evolution, marked by the relative development of illuvial and elluvial horizons, and that the landscapes are dominated by subsurface lateral flow. The data also suggested that atmospheric deposition may be an important contributor to pedogenesis in these landscapes and that there are expected hot-spots of nutrient accumulations in the mountainbase landscapes, where upland soils have transported and deposited dissolved ions and fine soil particles into wetland soils along riparian corridors. The next question became: does the distribution of elements along soil landscapes reflect what was expected from the aforementioned analyses and is the fate of elements controlled by the landscape positions? What is the balance between the atmospheric contributions to weathering and internal cycling of cations? Subsequently, the analysis for soils along the catenas was extended to model soil strain within the soil landscapes, quantify mass fluxes and distribution of elements within the soil landscapes, and quantify the atmospheric contributions to weathering in these systems. Results indicated that dilation in upper soil horizons reflect the textural patterns in the same horizons across all landscapes—supporting the notion that the soils along theses catenas have been strongly influenced by additions via atmospheric deposition, and this influence is detectable across entire hillslopes. Also, modeled soil strain indicated that great pedogenic additions have occurred in the mountainbase landscapes—supporting the notion that dissolved ions and fine soil material have been transported and deposited downslope via subsurface lateral flow. Calculated elemental flux values indicated that soil nutrients originating the upland landscape positions are transferred to lower landscapes through the mountainflanks, and are deposited in the mountainbase landscapes, where the soils were found to be enriched in the following major elements—Ca, Na, K, Al, Fe, and Mg. In turn, the impact of atmospheric contributions to soil landscapes along a catena was revealed. The data suggested that surface soil horizons are more strongly influenced by atmospheric contributions than subsurface horizons. Likewise, subsurface horizons are increasingly more influenced by the weathering of parent material moving from higher soil landscapes to lower soil landscapes. Lastly, results suggest that the isotopic signature within mountaintop soil landscapes is coupled to vegetative cover and snowfall and snowmelt hydrology dynamics. The soil catena model endures as a framework for providing insight into the relationships of soil forming factors across gradients of variation.