Mountain Scholar :: Browsing by Author "Paschke, Mark, committee member"

Browsing by Author "Paschke, Mark, committee member"

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Open Access
Amendment effects on soil physical properties and restoration of decommissioned forest roads
(Colorado State University. Libraries, 2017) Berlejung, John Michael, author; Fonte, Steven, advisor; Rhoades, Charles, committee member; Paschke, Mark, committee member
Unsealed forest roads, including logging roads and unauthorized roads created by hunters, miners, and recreational users, generate significant harmful effects to local ecosystems and waterways. Rapid restoration of these roads is necessary to prevent erosion, downstream implications for water quality, and a variety of other deleterious ecosystem impacts. Soil amendments, including mulches, composts, and other materials, offer promise to improve soil health, restore soil structure, and support revegetation of these sites. I tested the viability of three locally-sourced soil amendments wood straw mulch, Biosol fertilizer, and biochar alone and in paired combinations to restore soil physical properties important for improved hydrologic function and plant growth. I found that amendment combinations of biochar + mulch and biochar + Biosol significantly reduced soil bulk density when compared to unamended controls. Other factors (aggregate stability, infiltration, sediment production) suggested potential for improvement relative to unamended control plots, but no significant differences between treatments were observed due to high variability within and between sites. Regression analyses revealed that soil physical properties, particularly wet aggregate stability, was significantly correlated with key soil erosion parameters such as infiltration and runoff, suggesting aggregate stability could provide a useful measure of soil restoration success.
Open Access
Analysis of Ball Corporation's Fairfield can manufacturing plant and the potential for industrial wastewater recycling
(Colorado State University. Libraries, 2016) Medearis, Timothy G., author; Carlson, Kenneth, advisor; Catton, Kimberly, committee member; Paschke, Mark, committee member
Ball Corporation is an American manufacturing company based in Broomfield, CO, which is best known for its work in the aluminum can and packaging industry. Ball Corporation has a vision of becoming a more sustainable and environmentally responsible manufacturer around the globe. With this in mind, Ball Corporation approached Colorado State University in the spring of 2015 with a request to conduct a study on the feasibility of conserving water use in its manufacturing plants. This study is the result of that initial request. Ball Corporation’s can manufacturing plant in Fairfield, California was studied in three different phases. The first phase involved a water audit of the Fairfield plant. The can washers at the plant produce 80% of the plants wastewater and were quickly identified as the primary opportunity for recycling. City of Fairfield municipal water quality was characterized and set as the target water quality for the treatment and recycling process. By comparing the effluent industrial wastewater quality to the city’s municipal water quality, macro parameters of most concern such as suspended solids, total organic carbon (TOC), and dissolved solids were determined. Effluent water from the plant averaged a turbidity of 23 NTUs, a conductivity of 6.46 mS/µm, and a TOC of 105 mg/L, while the municipal water quality reported 0.065 NTUs, 0.346 mS/µm, and 2 mg/L of TOC. The second phase of the study involved the actual bench scale testing of treatment processes at CSU. From June 2015 to March 2016, ten different grab samples of industrial wastewater from the Fairfield plant were sent to CSU. These samples were treated through coagulation, filtration, granular activated carbon, and reverse osmosis processes. The main results suggested that chemical coagulation was effective in removing some suspended solids, but not TOC. Electrocoagulation showed more promise in removing TOC. Ultrafiltration was very effective at eliminating suspended solids, but was unable to reduce TOC. TOC concentrations remained high after 0.05 µm ultrafiltration and even after 1 kDa filtration. Granular activated carbon (GAC) was able to reduce and completely remove 100% of TOC concentration with high enough doses. This reduction of TOC, was helpful in reverse osmosis. Reduction in TOC with GAC proved to increase flux across the membranes and produce a more pure permeate. After bench testing, a full treatment train of electrocoagulation, ultrafiltration, GAC, and reverse osmosis was proposed. This treatment train produced water quality with a turbidity of 0 NTU, conductivity of 0.32 mS/µm, and a TOC of 0 mg/L. This matches the municipal water quality goal. The third phase of the project involved a cost analysis of the proposed treatment train. WaterTectonics, a water treatment company out of Everett, WA, assisted CSU in providing pilot scale treatment options for Ball to consider. A 20 GPM treatment train consisting of electrocoagulation, ultrafiltration, GAC, and reverse osmosis was compared to an identical treatment train without the electrocoagulation step. The price difference for Ball to consider between the two pilots was $30,000.
Open Access
Approaches for creating sustainable biomass production in a reclaimed fen in the Alberta Oil Sands Region, Canada
(Colorado State University. Libraries, 2019) Messner, Lewis Erwin, author; Cooper, David J., advisor; Paschke, Mark, committee member; Brown, Cynthia, committee member
Oil sands surface mining in the boreal region of Alberta, Canada alters the natural hydrologic processes, vegetation, and geochemistry of affected ecosystems. Peat accumulating bogs and fens cover approximately 30% of the oil sands region and function as long-term carbon sinks. The government of Alberta has legislated that disturbed areas be reclaimed to "equivalent land capacity." However, no guidelines exist for reclaiming peatlands in post-mined landscapes. A pilot fen was constructed on Suncor's Millennium oil sands mine in 2013 and I analyzed the effects on annual biomass growth by introducing plants as seeds, seedlings, and rhizome fragments from locally harvested material. Total above-ground biomass (AGB) in year five was 460 ± 30.7 g m-2 (n 56) and was comparable to natural fens in the region. Total living below-ground biomass (BGB) averaged 1640 ± 99.9 g m-2 (n 56) by year five, falling slightly below ranges for regional fens. When averaged across all treatments, C. aquatilis produced the greatest AGB (404 ± 32.8 g m-2, n 56) in year five and represented over 70% (se 1.520) of the site total biomass. AGB of C. aquatilis and J. balticus and total AGB and BGB were positively correlated with water table depth. Total BGB was positively correlated with electrical conductivity. Typha latifolia AGB was significantly affected by removal treatments when averaged across sampling years. Plant derived carbon inputs to reclaimed peatlands and long-term storage are characterized in part by the effects of abiotic variables on vascular plant biomass. Results from this study provide guidance for evaluating reclaimed post-mined fens in Alberta, Canada.
Open Access
Bacteriomes of peaches and cover crops
(Colorado State University. Libraries, 2024) Newberger, Derek R., author; Vivanco, Jorge M., advisor; Minas, Ioannis, advisor; Paschke, Mark, committee member; Manter, Daniel, committee member
Replant syndrome (RS) of fruit and nut trees causes reduced tree vigor and crop productivity in orchard systems due to repeated plantings of closely related tree species. Although RS etiology has not been clearly defined, the causal agents are thought to be a complex of soil microorganisms combined with abiotic factors and susceptible tree genetics. Different soil disinfection techniques alleviate RS symptoms by reducing the loads of the deleterious microbiome; however, the positive effect on crop growth is temporary. Here, the current understanding of RS in orchards from a soil microbiome perspective is reviewed. The resolution to RS will require experts to outline explicit descriptions for its symptoms, determine its etiology, identify the primary phytopathogens, and fully explore sustainable treatments which alleviate RS. Two sustainable treatments of RS were selected to explore at a deeper level, soil disinfection and increasing crop diversity to observe what technique could help establish a healthy soil bacteriome. In a greenhouse study, soil disinfection via autoclave was then followed by cover cropping. It was found that soil disinfection increases plant biomass as compared to the control for only the first crop cycle while non-autoclaved soils with a history of cover cropping alleviated RS in RS-susceptible 'Lovell' peach seedlings. Although soil disinfection via autoclave was found to distinctly alter the peach soil bacteriome for the full duration of the study, this sustainable practice mimicking solarization failed to provide relief from RS for peach seedlings. Instead of long-term benefits, differential abundance comparisons displayed a loss of potentially beneficial bacteria due to soil disinfection. Paenibacillus castaneae and Bellilinea caldifistulae were beneficial bacterial species that uniquely colonized peach rhizosphere of non-autoclaved soils with a cover crop history. As a promising sustainable technique, a greater understanding of how inter-/intra-specific competition of cover crops can influence the bulk soil bacteriome was pursued. Alfalfa, brassica, and fescue were grown in 7 different plant combinations (1. alfalfa, 2. brassica, 3. fescue, 4. alfalfa-brassica, 5. alfalfa-fescue, 6. brassica-fescue, 7. alfalfa-brassica-fescue) across 3 density concentrations (low: 1–3 plants, medium: 24 plants, and high: 48 plants) for a greenhouse microcosm experiment. It was found that even in highly competitive conditions beneficial bacteria were enriched, however, there was an apparent trade-off where different plant combinations enriched distinct beneficial bacteria. As an example, even if a free-living nitrogen fixing bacteria such as an Azospirillum spp. was enriched in the bulk soil of alfalfa and brassica monocultures, it was not enriched in the bulk soil of an alfalfa-brassica plant mixture. Instead Pseudarthrobacter phenanthrenivorans, a phytohormone producer, was enriched in alfalfa-brassica plant mixtures. When zooming into the rhizosphere compartment of these microcosms, it was found that regardless of plant neighbor identity or density, a few rhizobacteria were highly correlated with a specific plant species. Meanwhile, certain plant species specific rhizobacteria were enriched only if specific conditions such as plant neighbor identity or density were met. Overall, our research found that growing diverse plant species plants prior to the re-establishment of a peach orchard could alleviate RS symptoms. Furthermore, cover crops can enrich different microbes when grown together as opposed to when grown separately. Lastly, although plants recruit a particular set of bacteria, this recruitment can shift depending on plant neighbor identity or density. Further study of cover crops may identify how they can alleviate RS in orchards worldwide.
Open Access
Bird and mammal response to large-scale habitat mitigation for game species in the oil and gas fields of northwest Colorado
(Colorado State University. Libraries, 2016) Gallo, H. Travis, author; Pejchar, Liba, advisor; Noon, Barry, committee member; Paschke, Mark, committee member; Wittemyer, George, committee member
To view the abstract, please see the full text of the document.
Open Access
Diagenesis, composition and porosity of the upper Three Forks Formation, Williston basin, North Dakota and Montana
(Colorado State University. Libraries, 2014) Kolte, Ketki, author; Egenhoff, Sven, advisor; Ronayne, Michael, committee member; Paschke, Mark, committee member
The upper part of the Three Forks Formation in the Williston basin of North Dakota and Montana is one of the prime targets for oil exploration in the onshore part of the US today. The unit is mainly composed of dolomite, yet the details of dolomite formation and its relative timing are unknown. This study is the first that combines an analysis of cement generations and porosity to develop a diagenetic scheme based on detailed microscopical observations. The upper Three Forks Formation shows a total of seven dolomite generations along with some anhydrite and pyrite. Most of the rock consists of an inclusion-rich dolomite, likely dolomite II, that forms mm- to sub-mm-size rhombic crystals showing overgrowth of five more alternating clear and inclusion-rich dolomite generations, and in places a core of iron-rich dolomite I. Porosity types in the upper Three Forks Formation are intercrystalline, intracrystaline, and "moldic" which here stands for the dissolution of entire dolomite crystals. Detrital components are quartz, feldspars, mica, and clay particles. The Three Forks Formation was most likely deposited on a mixed carbonate-siliciclastic ramp as a limestone unit with varying amounts of detrital input. Initial replacement of limestone into dolomite probably occurred early entirely changing the texture of this unit. Several dolomite phases occurred during burial post-dating early dolomitization. The effective porosity, characterized by intercrystalline and "moldic" pores, is linked to the dolomitization, most likely originally to an early event as no late dolomite is seen filing these pores. Up to centimeter-size voids, though, representing mostly non-effective porosity is generally partly filled with several generations of dolomite and leaving some part of the vugs open. This indicates that most likely the voids were formed before the last few generations of dolomite cement, and also that not all open space was easily occluded by these dolomitizations but left some of the porosity untouched. Based on a limited data set, porosity distribution in the upper Three Forks Formation does not show a clear link to the distribution of dolomite. However, it does show a trend to overall increased values from the east (less than 1%) to the west (around 5%) with a north-south extending zone of maximum porosities (about 10-12%) around 103.5°. It is therefore likely that potential hot spots in this basin are rather located in western ND while towards the east porosities are lower.
Open Access
Ecological aspects of plant selenium hyperaccumulation: effects of selenium hyperaccumulation on plant-plant interactions
(Colorado State University. Libraries, 2016) Mehdawi, Ali Farag El, author; Pilon-Smits, Elizabeth, advisor; Pilon, Marinus, committee member; Paschke, Mark, committee member; Vivanco, Jorge, committee member
Hyperaccumulators are plants that accumulate toxic elements to extraordinary levels. Selenium (Se) hyperaccumulators such as Astragalus bisulcatus and Stanleya pinnata can contain 0.1-1.5% of their dry weight in Se (1,000 - 15,000 mg Se kg-1 DW), levels toxic to most other organisms. Selenium promotes hyperaccumulator growth and also offers the plant several ecological advantages through negative effects on Se-sensitive partners. Previous work has shown that high tissue Se levels reduce herbivory and pathogen infection. On the other hand, hyperaccumulators may offer an exclusive niche for Se-tolerant ecological partners. The focus of this dissertation study was on the effects of Se hyperaccumulation on plant-plant interactions. The first Chapter presents a literature review of the phenomenon of Se hyperaccumulation, how Se hyperaccumulators are different from other plants, and an overview of previous studies on the effects of hyperaccumulated Se on ecological processes related to herbivore-plant interactions, microbe-plant interactions and pollinator-plant interactions. In addition, evolutionary aspects of Se hyperaccumulation are discussed, and their implications for their ecological partners. The findings presented in this overview formed the platform for the experiments carried out in this dissertation research, on the topic of plant-plant interactions. In Chapter 2, experiments are described to address the question whether Se hyperaccumulation can negatively affect neighboring plants. Soil collected around hyperaccumulators on a seleniferous field site was measured and shown to contain more Se (up to 266 mg Se kg-1) than soil around non-hyperaccumulators. Vegetative ground cover was somewhat lower around Se hyperaccumulators compared to non-hyperaccumulators. Thus, Se hyperaccumulators may increase surrounding soil Se concentration (phytoenrichment). The enhanced soil Se levels around hyperaccumulators were shown to impair growth of a Se-sensitive plant species, Arabidopsis thaliana, pointing to a possible role of Se hyperaccumulation in elemental allelopathy. In Chapter 3, potential positive effects of hyperaccumulator Se on neighboring plants are explored. It was found for two plant species, Artemisia ludoviciana and Symphyotrichum ericoides, that growing next to Se hyperaccumulators increased their Se content 10-20 fold (up to 800-2,000 mg Se kg-1 DW) compared to when they were growing next to non-accumulators. Moreover, these neighbors of hyperaccumulators were 2-fold bigger, showed 2-fold less herbivory damage and harbored 3-4 fold fewer arthropods than when growing next to non-hyperaccumulators. When used in laboratory choice and non-choice grasshopper herbivory experiments, Se-rich neighbors of hyperaccumulators experienced less herbivory and caused higher grasshopper Se accumulation (10-fold) and mortality (4-fold). These results suggest that Se hyperaccumulators can facilitate the growth of Se-tolerant neighboring plants. The fourth Chapter describes a more controlled greenhouse pot cocultivation study that investigated how Se affects relationships between Se hyperaccumulators (A. bisulcatus and S. pinnata) and related non-accumulator species (A. drummondii and S. elata), in terms of how these plants influence their neighbor’s Se accumulation and growth. Selenium affected growth differently in hyperaccumulators and nonaccumulators: The hyperaccumulators performed 2.5-fold better on seleniferous than non-seleniferous soil, and grew up to 4-fold better with increasing Se supply, while the non-accumulators showed opposite results. Both hyperaccumulators and non-accumulators could affect growth (up to 3-fold) and Se accumulation (up to 6-fold) of neighboring plants. The mechanisms for these effects are largely unknown but may involve concentration of soil Se via exudation, root turnover and litter deposition. Exudate of selenate-supplied A. bisulcatus was shown by x-ray absorption spectroscopy to contain mainly C-Se-C. In conclusion, Se hyperaccumulators may enhance the soil Se levels under their canopy, and also convert inorganic Se to organic Se. The Se-enriched soil around hyperaccumulators enhances Se levels in neighboring plants, which may negatively affect Se-sensitive neighboring plants via toxicity, but facilitate Se-tolerant neighbors through reduced herbivory. The latter is an interesting finding, as it constitutes facilitation via enrichment with a non-essential element. It is also interesting that Se enrichment of neighbors by hyperaccumulators can result in competition when neighbors are Se-sensitive and in facilitation when neighbors are Se-tolerant. Via these competitive and facilitating effects, Se hyperaccumulators may affect plant species composition and, consequently, higher trophic levels. Hyperaccumulators may favor Se resistant species at different trophic levels, while selecting against Se sensitive species. If indeed Se hyperaccumulators affect soil Se distribution and speciation and local species composition and Se tolerance, Se hyperaccumulators may play an important role in Se entry into and Se cycling through their seleniferous ecosystems.
Open Access
Ecological effects of selenium hyperaccumulation on plant community structure and potential implications for selenium cycling
(Colorado State University. Libraries, 2019) Reynolds, Ray Jason Bixler, author; Pilon-Smits, Elizabeth, advisor; Paschke, Mark, committee member; von Fischer, Joseph, committee member; Steingraeber, David, committee member
To view the abstract, please see the full text of the document.
Open Access
Ecological interactions involving plant selenium hyperaccumulation
(Colorado State University. Libraries, 2010) Quinn, Colin Francis, author; Pilon-Smits, Elizabeth, advisor; Paschke, Mark, committee member; Seshadri, Arathi, committee member; Steingraeber, David, committee member
To view the abstract, please see the full text of the document.
Open Access
Engelmann spruce and subalpine fir stand dynamics in north central Colorado
(Colorado State University. Libraries, 2015) Derderian, Drew Phillip, author; Binkley, Daniel, advisor; Paschke, Mark, committee member; Rocca, Monique, committee member
Stemwood biomass and production were measured in a 600-year chronosequence of stands consisting of Engelmann spruce and subalpine fir in the Colorado Front Range. The stands were part of a chronosequence established and measured in 1984. The original chronosequence showed near-constant biomass of spruce after approximately 250 years of development. Spruce production also had remained nearly constant after an initial rise and fall during the first 250 years. Fir biomass decreased more than that of spruce after around 150 years. Fir biomass remained at lower consistent sub-dominate values through the end of the chronosequence. Fir's high production from early stand development decreased and remained constant after approximately 175 years of development. Changes over the most recent 29 years did not follow the patterns in the 1984 chronosequence: spruce biomass dropped by 70% with little change in fir biomass. This resulted in a 47% average decrease in total stand biomass since 1984. Stand biomass showed no relationship with stand age. Spruce beetle-kill appeared to have played a major role in live biomass decline in all stands. Net increment was negative in fir as increases in fir production were more than offset by fir mortality. The stands investigated have developed from post-fire initiation and, although there was no evidence of subsequent major disturbance in 1984, severe beetle infestation since then has altered expected trends in spruce-fir forest structure. Stand age pattern projections will likely continue to be altered by disturbances and changing disturbance regimes.
Open Access
Exploring interactions among biological soil crusts, plant germination, and morphological seed traits: implications for plant community assembly and dryland restoration
(Colorado State University. Libraries, 2023) Bacovcin, John, author; Havrilla, Caroline, advisor; Ocheltree, Troy, committee member; Wrighton, Kelly, committee member; Paschke, Mark, committee member
Arid and semi-arid (dryland) ecosystems make up over 40% of our plant's terrestrial surface and are incredibly vulnerable to land degradation. To combat dryland degradation, active plant and soil restoration is often needed and the role of plant-soil microbe interactions can be key to dryland restoration trajectories. Within drylands, biological soil crusts (biocrusts), collections of cyanobacteria, algae, lichen, and moss are key surface communities that influence soil processes (e.g., stability, nutrient cycling, hydrology) and can thereby strongly influence recruitment of dryland plants. These biocrusts may interact with plant functional traits (i.e., seed morphological traits), and these interactions can influence germination. However, much is still unknown about mechanisms that underlie these interactions and how plant functional traits mediate effects of biocrusts on plant germination. To investigate these knowledge gaps, I conducted two studies: (Chapter 1) a global meta-analysis of the role of morphological seed traits in determining biocrust effects on germination, and (Chapter 2) a full-factorial greenhouse study examining the effects of biocrust inoculum cover treatments and plant functional traits on plant recruitment to investigate questions about how biocrust heterogeneity and biotic components of biocrusts in the context of restoration. To explore effects of morphological seed traits on plant germination responses to biocrusts (Ch. 1), we compiled a global database of 491 studies of biocrust effects on plant germination encompassing 101 unique plant species and their associated morphological seed traits. For the greenhouse study (Ch. 2) we seeded two seed mixes on three different inoculum cover treatments (i.e., 0%, 30%, and 100%) using both biologically active (live) and autoclaved biocrust inoculum, to assess effects of cover heterogeneity, biological biocrust activity, and plant functional traits on percent germination. Results from the meta-analysis showed that morphological seed traits do mediate plant germination responses to biocrusts, and that, in general, germination of smaller seeded species with appendages was increased by biocrusts. Results from the greenhouse study showed that, in a restoration context, increasing cover of biocrust inoculum increases plant germination, and that these effects were explained by physical rather than biotic effects of inoculum on germination. As in Chapter 1, we found that biocrusts effect on germination differed across plant functional groups and that seed traits also influenced germination responses to biocrust inoculum cover treatments. Together, both studies showed that morphological seed traits mediate effects of biocrusts on plant germination. These findings increase understanding of the role of biocrusts in determining dryland plant community assembly and have implications for dryland restoration.
Open Access
From litter decomposition to soil organic matter formation: using stable isotopes to determine the fate of carbon and nitrogen
(Colorado State University. Libraries, 2014) Horton, Andrew James, author; Cotrufo, M. Francesca, advisor; von Fischer, Joseph, committee member; Paschke, Mark, committee member
Litter decomposition releases the energy and nutrients fixed during photosynthesis into the atmosphere and soil. In the soil, carbon and nitrogen from the litter can be stabilized in soil organic matter pools, which globally represent large pools of both carbon (C) and nitrogen (N). Soil organic matter pools are heterogeneous, the product of different stabilization processes and will stabilize C and N for periods of time ranging from years to millennia. A thorough mechanistic understanding of the fate of above-ground litter C and N is essential to understand how climate change could affect both carbon sequestration and soil health. This research studied the fate of litter derived organic matter. Isotopically labeled litter was used in a field incubation to trace litter derived C and N into different SOM pools and soil depths over the course of 3 years. Additionally, naphthalene was used to suppress microarthropods to determine the impact of mesofauna on the fate of litter derived N. In the laboratory, soil from the field experiment was incubated for 150 to determine how different SOM pools contributed to respiration and leaching. Microarthropods do not increase overall N mineralization rates, but do influence the fate of litter derived N. When present, microarthropods increased the amount of litter derived N in the light fractions, suggesting that microarthropods increase litter fragmentation. Surprisingly, litter derived organic matter does not contribute to respiration and leaching equally, suggesting that leaching and respiration are not directly related. Litter derived OM behaves differently than older OM present in the soil, with the newer litter derived C and N being more readily lost from SOM pools. This result supports the onion layering model suggested by Sollins (Sollins et al. 2006). In order to create more accurate models, microarthropods and the onion layering model should be included in future C and N dynamic studies.
Open Access
Impacts and management of the invasive Russian olive (Elaeagnus angustifolia L.) in a hereogenous riparian ecosystem
(Colorado State University. Libraries, 2017) Tuttle, Graham, author; Norton, Andrew, advisor; Katz, Gabrielle, advisor; Meiman, Paul, committee member; Paschke, Mark, committee member
Russian olive is an exotic actinorhizal tree intentionally introduced to the U.S. in the early 1900's. It has become a dominant component of riparian ecosystems throughout the western U.S. Unlike most other riparian trees in the semi-arid west, Russian olive germinates and grows both in the open and in the understory of mature cottonwood stands. As an actinorhizal species, it forms an endosymbiosis with soil actinobacteria in the genus Frankia that allows for atmospheric N2-fixation. This leads to higher soil N concentrations and mineralization rates underneath the tree's canopy than outside. Russian olive's high abundance and impact on soil N suggest it may alter plant communities, but these impacts have not been previously demonstrated. I investigated the impacts of Russian olive on shading, soil N availability, and plant communities and documented how those impacts varied across a semi-arid riparian ecosystem along the South Fork of the Republican River in eastern Colorado. Of the suite of environmental variables I measured, presence or absence of cottonwood canopy had the largest effect on Russian olive impacts. Russian olive increased shading, soil N availability, and proportion exotic plant and forb cover more in the open than underneath a cottonwood overstory. Actinorhizal endosymbioses provides an important N source in terrestrial ecosystems, but N2-fixation rates decrease due to high exogenous N and low photosynthetically active radiation (PAR). The amount that these environmental variables reduce N2-fixation in host-Frankia symbiosis types dictates the strength and duration of those symbioses' impacts on ecosystems. To understand how the two main types of endosymbioses (Alnus- and Elaeagnus-Frankia) differ in their response to environmental variability, I conducted a greenhouse experiment comparing growth and nodulation between two genera of actinorhizal species, Elaeagnus and Alnus, across exogenous N and PAR levels. Overall, Elaeagnus species had higher nodulation rates and tissue % N than Alnus species. Nodulation rate and growth response to nodulation were both lower at low PAR than high PAR for both genera. The reduction in the growth response to nodulation at high exogenous N was lower in Elaeagnus-Frankia symbiosis than Alnus-Frankia symbiosis. These results suggest that Elaeagnus species are more likely to cause a greater and longer-lasting increase in soil N than Alnus species. A main objective of exotic species management is to increase native plant cover. However, few studies monitor plant community response to exotic species management, and the few that have suggest secondary invasion is likely, particularly when effects of the target invasive persists and management efforts cause disturbance. To measure the role of these two factors in plant community response to Russian olive removal, I monitored soil N availability and plant communities along the South Fork of the Republican River two years before and three years after the tree's removal. Russian olive's impact on soil N availability persisted, with levels staying high around removed Russian olive stems three years after removal. The plant community around removed Russian olive also had no increase in native plant cover but a dramatic increase in kochia (Bassia scoparia) cover following removal. My research demonstrates that Russian olive increases exotic plant cover in areas it invades and simply removing the tree does not promote native species recovery.
Open Access
Improving ungulate habitat in a region undergoing rapid energy development: consequences for songbirds and small mammals
(Colorado State University. Libraries, 2014) Bombaci, Sara Petrita, author; Pejchar, Liba, advisor; Wilson, Kenneth R., committee member; Paschke, Mark, committee member
Habitat manipulation intended to mitigate the impact of energy development on game animals is well underway in the western U.S. Yet, the consequences of these actions for other species are not well understood. A habitat manipulation experiment was established in the Piceance Basin, a region of Colorado undergoing rapid energy development, to evaluate alternative methods (i.e. chaining, hydro-axe, and roller-chop treatments) for reducing pinyon-juniper woodlands to promote mule deer habitat. I use this experimental design to additionally test the initial effects of these treatments on birds and small mammals, and to evaluate selection of habitat components in treatments by birds and small mammals. I found lower bird species occupancy in all treatment plots compared to control plots; however the strength of this response varied by bird guild. I found a positive relationship between bird species occupancy and percent tree cover and a negative relationship between bird species occupancy and percent grass and forb cover. I found no evidence of differences in small mammal species occupancy or density between controls and treatments. I found a positive relationship between small mammal species occupancy and percent grass and forb cover. Species richness did not significantly differ between control and treatment plots for birds or small mammals. My approach and research findings can be used to inform habitat management and multiple-species conservation objectives in pinyon-juniper and sage-steppe ecosystems undergoing energy development. Specifically, I have identified that recently developed roller-chop and hydro-axe treatments have similar impacts to woodland bird guilds as traditional chaining treatments. I have also identified species that are sensitive to habitat mitigation treatments, and thus should be monitored if woodland reduction continues to be used as a habitat mitigation strategy. Since all bird guilds were positively associated with tree cover, woodland reduction strategies that promote landscape heterogeneity by leaving standing trees to provide structure for birds may have fewer impacts than those that clear large contiguous patches of woodland. This approach has the potential to increase the conservation value of habitat mitigation treatments for pinyon-juniper obligates as well as shrubland and grassland species.
Open Access
Land of 10,000 pixels: applications of remote sensing & geospatial data to improve forest management in northern Minnesota, USA
(Colorado State University. Libraries, 2018) Engelstad, Peder, author; Falkowski, Michael, advisor; Lefsky, Michael, committee member; Paschke, Mark, committee member
The use of remote sensing and geospatial data has become commonplace in a wide variety of ecological applications. However, the utility of these applications is often limited by field sampling design or the constraints on spatial resolution inherent in remote sensing technology. Because land managers require map products that more accurately reflect habitat composition at local, operational levels there is a need to overcome these limitations and improve upon currently available data products. This study addresses this need through two unique applications demonstrating the ability of remote sensing to enhance operational forest management at local scales. In the first chapter, remote sensing products were evaluated to improve upon regional estimates of the spatial configuration, extent, and distribution of black ash from forest inventory and analysis (FIA) survey data. To do this, spectral and topographic indices, as well as ancillary geospatial data were combined with FIA survey information in a non-parametric modeling framework to predict the presence and absence of black ash dominated stands in northern Minnesota, USA. The final model produced low error rates (Overall: 14.5%, Presence: 14.3%, Absence: 14.6%; AUC: 0.92) and was strongly informed by an optimized set of predictors related to soil saturation and seasonal growth patterns. The model allowed the production of accurate, fine-scale presence/absence maps of black ash stand dominance that can ultimately be used in support of invasive species risk management. In the second chapter, metrics from low-density LiDAR were evaluated for improving upon estimates of forest canopy attributes traditionally accessed through the LANDFIRE program. To do this, LiDAR metrics were combined with a Landsat time-series derived canopy cover layer in random forest k-nearest neighbor imputation approach to estimate canopy bulk density, two measures of canopy base height, and stand age across the Boundary Waters Canoe Area in northern Minnesota, USA. These models produced strong relationships between the estimates of canopy fuel attributes and field-based data for stand age (R2 = 0.82, RMSE = 10.12 years), crown fuel base height (R2 = 0.79, RMSE = 1.10 m.), live crown base height (R2 = 0.71, RMSE 1.60 m.), and canopy bulk density (R2 = 0.58, RMSE 0.09 kg/m3). An additional standard randomForest model of canopy height was less successful (R2 = 0.33, RMSE 2.08 m). The map products generated from these models improve upon the accuracy of national available canopy fuel products and provide local forest managers with cost-efficient and operationally ready data required to simulate fire behavior and support management efforts.
Open Access
Lessons in establishing plant communities on constructed fens for oil sands mine reclamation
(Colorado State University. Libraries, 2018) Borkenhagen, Andrea, author; Cooper, David J., advisor; Paschke, Mark, committee member; Vitt, Dale, committee member; Smith, Melinda, committee member
The third-largest proven oil deposit in the world is in Alberta, underlying 142,000 square kilometers of Canada’s boreal covered by forested uplands and peatland basins. The vast deposit is in the form of oil sands that consist of a mixture of sand, water, clay and oil. Where oil sands are near surface, they are excavated in open-pit mines that remove the overburden landscape to extract the resource. Reclamation is a legislative condition for oil sands operators to replace ecosystems that are lost. This involves recontouring the surface to recreate landscape processes and introducing plant species common in regional reference sites. Fen peatlands are the most dominant ecosystem type but provincial standards have allowed compensation with marsh wetland as they are easier to create. Oil sands extraction and reclamation is highly controversial with opponents suggesting that destroyed peatlands will not be restored. Scientists, operators and regulators are more aware that peatland reclamation is critical and despite the constraints, research is underway in two reclamation fens that have recently been constructed. To effectively reclaim fens, we need to understand how plant species and communities respond to environmental gradients, the most effective methods to introduce species, and which success criteria are achievable. In the following chapters, I examine drivers of plant community assembly in natural and reclaimed fens and consequences of abiotic, biotic, and construction constraints on ecosystem structure and function. A major constraint in fen reclamation is achieving optimal surface topography and seasonal water table position to support desired plants. Moss-dominated fens are the most common regional peatland type and evaluating the response of mosses to submergence in natural fens provides insight into species selection and processes of recovery for reclaimed fens. I conducted a field experiment to determine the short and long-term tolerances of four fen mosses to submergence from 1 to 8 weeks. I found that moss species vary in their responses to submergence duration and that shifts in community composition that support tolerant dominant species such as Tomentypnum nitens increased moss community resilience and provide stability in boreal fen ecosystems. As part of a multi-stakeholder collaboration, the first self-sustaining reclamation fen and associated watershed was constructed within an oil sands mine site north of Fort McMurray, Alberta. To determine the most effective approach to establish fen plants, I designed and implemented a large-scale multifactorial field experiment that tested introducing moss layer transfer material (MLT), seeds, and seedlings under wood-strand mulch and with a Typha latifolia weeding treatment. Four years after planting, the MLT and Juncus balticus seedling treatment supported the highest fen bryophyte and vascular plant cover and species richness. Weeding did reduce T. latifolia cover but was not necessary in areas where seedlings or MLT was introduced. The most successful fen species to establish was C. aquatilis, which rapidly colonized but also reduced cover and richness of bryophytes and other vascular plants. To provide a broader context, I examined vegetation establishment across the two reclaimed fens that had different water level gradients and species introduction approaches. Despite differences, peat-accumulating bryophyte and vascular plant communities developed in both fens. Community convergence occurred due to dominance of C. aquatilis, and community divergence occurred in response to water level gradients. Dominant species adapted to site conditions can be introduce by basic approaches such as seeding. Intensive approaches such as planting seedlings or spreading MLT should be prioritized in areas of overlap along water level gradients between desirable and undesirable communities to deter establishment of non-peat forming species. Bryophyte cover and desirable species richness was highest following intensive approaches and where the summer water level was -10 cm to -40 cm from the soil surface. My research shows that it is possible to reclaim peat-accumulating bryophyte and vascular plant communities in the post-mining landscape of Alberta and that a range of successful outcomes are achievable. Previous assertions that fens cannot be reclaimed after mining activities are antiquated as large-scale construction designs and species introduction approaches are actively underway and the results are proven.
Open Access
Recreating peatland initiation conditions: methods for reclaiming peatlands in Alberta's oil sands region
(Colorado State University. Libraries, 2014) Borkenhagen, Andrea K., author; Cooper, David J., advisor; Paschke, Mark, committee member; Butters, Greg, committee member
Northern Alberta's oil sands deposit is the largest in the world and mining operations remove vast areas of upland forests and peatland ecosystems. Reclaiming peatland ecosystems is challenging as it takes thousands of years to reestablish peat soils to pre-disturbance extents. Practical approaches that are easy to implement are required to reclaim the tens of thousands of peatland hectares that have been lost to mining activities. My research focuses on developing reclamation methods that recreate peatland initiation conditions on mineral soil and apply assisted succession techniques by introducing mosses, plants and woody cover. I evaluated the regenerative abilities of five common fen mosses introduced in a 1:10 mixture to clay loam mineral soil. To evaluate optimal hydrologic conditions for moss species establishment, I tested four water levels below the soil surface (0, -10, -20, and -30 cm). I recreated plant communities and microclimates similar to those found during peatland initiation to determine those that increased moss species establishment by comparing cover treatments of herbaceous plants, woody plants, and WoodStraw® (wood-strand) mulch. After two seasons of growth, fen mosses established and grew to an average of 20 percent cover on mineral soils. Total moss cover was not significantly different between 0cm and -30 cm water levels but species distribution was as depth to the water table was the most important factor influencing establishment. Drepanocladus aduncus was most common when the water level was 0 cm and Aulacomnium palustre was most common in the -30 cm water level. Tomentypnum nitens had five times greater cover than any other moss. Moss species cover and height was greatest under herbaceous plants and at 0 cm water level. Wood-strand mulch reduced the cover of salt that precipitated on the soil surface, which also increased as the water table deepened. Implications to peatland reclamation include selecting a mixture of mosses to adapt to chemical and hydrologic variations and planting herbaceous plants and or applying wood-strand mulch to improve moss establishment on mineral soil. Peatlands may take thousands of years to develop, but reclaiming a carbon-accumulating ecosystem and establishing the foundations for peatland succession is possible. The applications described here provide economical and practical strategies to reconstruct pre-existing peatland ecosystems in Alberta's oil sands region.
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 member
Inorganic 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.
Open Access
Selenium accumulation in plants and implications for human health: a survey of molecular, biochemical, and ecological cues
(Colorado State University. Libraries, 2022) Lima, Leonardo Warzea, author; Pilon-Smits, Elizabeth, advisor; Schiavon, Michela, committee member; Pilon, Marinus, committee member; Antunes, Mauricio, committee member; Paschke, Mark, committee member
To view the abstract, please see the full text of the document.
Open Access
Small mammal populations and plant community succession at artesian well sites in Great Sand Dunes National Park, Colorado
(Colorado State University. Libraries, 2013) Garza, Sarah Julía, author; Bowser, Gillian, advisor; Wilson, Kenneth R., advisor; Doherty, Paul F., committee member; Paschke, Mark, committee member
For more than 100 years, artificial artesian wells in the San Luis Valley of south-central Colorado have been a steady source of water for livestock and wildlife on lands administered by Great Sand Dunes National Park and The Nature Conservancy. In summer 2011, a study was established to examine effects on local biota of capping the artesian wells in 2010. In Chapter 1, I focused on the short-term effects of capping artesian well sites and the effects on the population dynamics and species diversity of small mammals. In 2011 and 2012, I compared newly capped well sites, well sites with water, and reference sites by estimating density (Program DISTANCE), survival (Cormack-Jolly-Seber Model in Program MARK), species occupancy (Robust Occupancy Model in Program MARK), and measures of species diversity (species richness, Shannon-Weiner index, and species evenness) of small mammals. I modeled small mammal density and survival as a function of well site type, percent plant cover, disturbance level from ungulates, and year of study using an information theoretic approach to rank models and estimate the relative importance of the independent variables. Over the two years, I captured 1,150 individuals of 6 rodent species; however, only two species, Ord's kangaroo rat (Dipodomys ordii) and Apache or plains pocket mice (Perognathus sp.), had sufficient numbers for density and survival analyses. There was no significant difference in density and survival estimates for these species at the well types; however species occupancy estimates varied by well type and by species such that open well sites had the greatest probability of occupancy of the deer mouse (Peromyscus maniculatus), and reference sites had the greatest probability of occupancy of the thirteen-lined ground squirrel (Spermophilus tridecemlineatus). For the kangaroo rat density and survival, the type of well site was important with greatest values at capped well sites. For pocket mice, the disturbance level by ungulates and year of study were important predictors of density and survival; density was negatively correlated with amount of disturbance and survival nearly doubled from 2011 to 2012. Richness, the Shannon-Weiner diversity index and community evenness values were greatest at reference sites. Results suggest that in the short term, small mammal density and survival does not increase after a well is capped, species occupancy is variable, and diversity does not change. Additional studies are needed to provide a better understanding of the long-term changes in small mammal population dynamics and biodiversity as capped well sites continue to revert to habitats similar to reference sites. In Chapter 2, I concentrated on the short-term effects of capping wells on the plant community with a focus on secondary ecological succession. I characterized the habitats at sampled sites by identifying plant species (native and exotic) and examining potential sources of variation by modeling plant cover and species frequency as a function of variables such as well site type, the ungulate disturbance level, distance from well heads, and the year of study. I used an information theoretic approach to rank models and estimate the relative importance of these independent variables. I also estimated indices of native species diversity including richness, Shannon-Weiner diversity index, Simpson's index, community evenness, and compared patterns of plant form cover (i.e., shrubs, forbs, and grasses) at increasing distances from well heads. Year of study and distance from well heads were important predictors of native plant cover and exotic plant cover, respectively; however there was no difference in native or exotic plant cover based on well status (open or closed). Well site type, year of study, and ungulate disturbance intensity levels were important predictor variables for native species frequency whereas for exotic species frequency, well type was important. All indices of species diversity values were greatest at the reference sites. Capped well sites had varying distance patterns across different plant forms whereas all plant cover was highest at the farthest distances from open well heads. Overall, this study suggested that while plant communities at well sites are not significantly different after capping the well head, the abundant exotics may need additional control efforts for the community to return to species composition typical of the sand sheet ecosystem.