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Browsing by Author "Paschke, Mark W., committee member"

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    Cheatgrass (Bromus tectorum L.) management and native plant community recovery on sites selectively treated with Imazapic in Rocky Mountain National Park
    (Colorado State University. Libraries, 2017) Davis, Christopher, author; Brown, Cynthia S., advisor; Paschke, Mark W., committee member; Fernandez-Gimenez, Maria, committee member
    Cheatgrass, a winter annual grass introduced to North America from Eurasia, has invaded much of the Western United States over the last century. Recently, cheatgrass has become a threat to the montane and subalpine plant communities and ecosystems of Rocky Mountain National Park (RMNP). Cheatgrass aggressively invades disturbed sites and competes with native plant species by rapidly establishing a root system capable of depleting soil moisture and available nitrogen, making cheatgrass control a priority when restoring disturbed areas within RMNP. The purposes of this study were to determine the effectiveness of imazapic for cheatgrass control, its effects on non-target native species, and how the plant community recovers following cheatgrass control. In 2008, 12 permanent monitoring plots were established in six sites in RMNP, each with one reference and one imazapic treatment plot. Reference plots were chosen to represent the desired final condition for each imazapic treatment site. Imazapic (23.6% a.i.) was applied to cheatgrass infestations post-emergence in 2008 (105 g a.i./ha) and pre-emergence in 2009 (105 g a.i./ha) and 2010 (70 g a.i./ha). Imazapic was applied to cheatgrass patches selectively, avoiding application to native species as much as possible. Cheatgrass cover was reduced more than fourfold to approximately 5% in 2013, and there was no decrease in cover of native forbs, grasses, or shrubs. There was no subsequent increase in native species abundance following cheatgrass removal, suggesting further action is needed if the ultimate management goal is to encourage native species recovery in treatment plots after satisfactory cheatgrass control is achieved.
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    Emergence of seeded forbs in established stands of Geyer's larkspur on Colorado rangelands
    (Colorado State University. Libraries, 2013) Schroeder, Jesse D., author; Meiman, Paul J., advisor; Paschke, Mark W., committee member; Brummer, Joe E., committee member
    Larkspurs (Delphinium spp.) are considered by many to be the most damaging poisonous plants on rangelands in the western United States. Larkspurs are palatable and acutely toxic to cattle resulting in a consistently large number of annual cattle deaths on western rangelands in the United States. Attempts to avoid the toxic effects of larkspurs often result in missed opportunities to harvest considerable amounts of high-quality forage and dictate management of infested rangelands. Herbicide application can effectively reduce larkspur, but also reduces other herbaceous plants expected to compete most directly with larkspur for resources, so recovery of larkspur following herbicide application is common. A field study was conducted in the foothills of northern Colorado to determine whether seeded forbs would emerge after being sown into existing stands of Geyer's larkspur (Delphinium geyeri), and whether pre-seeding application of two herbicides at light-rates would reduce initial competition from larkspur and increase emergence of seeded forbs. Seedling emergence of native forbs was compared to introduced forbs in sprayed (2 different herbicides) and unsprayed stands of Geyer's larkspur. Experimental plots were randomly assigned one of nine possible treatment combinations and replicated 3 times in each of 3 locations. The treatments consisted of all possible combinations of seeding (native forb mixture, introduced forb mixture, and unseeded), herbicide (2,4-D LV4, picloram, and unsprayed) and location (1, 2, and 3). Larkspur density was consistently reduced by herbicide at all locations regardless of seed mixture and no difference was detected between the two herbicides. Perennial grasses were unaffected by herbicide and seeding treatments. Treatment effects on larkspur canopy cover were not obvious. At 2 of the 3 locations, larkspur canopy cover in unsprayed plots was similar to one or both herbicide treatments. At the third location, larkspur canopy cover in plots treated with picloram was less than 2 of the 3 unsprayed plots and less than all three plots treated with 2,4-D. 2,4-D reduced canopy cover of non-target forbs compared to the unsprayed plots at all three locations, and also compared to the picloram treatment at two locations. Canopy cover of non-target forbs in plots treated with picloram was similar to unsprayed plots at 2 of the 3 locations, and reduced at the other. Sub-shrub cover was greatest in unsprayed plots and reduced by picloram and 2,4-D at 2 of 3 locations. Seedling density of seeded forbs was very low and dependent on location, herbicide, and seed mixture but the effects were variable and subtle. Results suggest that both herbicides reduced larkspur and other existing broadleaf species. The picloram treatment seemed to be more effective at reducing larkspur while leaving greater non-target forb cover than 2,4-D. However, there are indications of a slight reduction in seedling density of seeded forbs in the picloram treated plots.
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    Evaluation of spring wheat genotypic response to soil health promoting management practices
    (Colorado State University. Libraries, 2017) Junaidi, Fnu, author; Fonte, Steven J., advisor; Byrne, Patrick F., committee member; Paschke, Mark W., committee member
    Growing efforts to restore soil organic matter and overall soil health are likely to enhance soil biological communities and promote positive interactions between plants and soil communities. However, modern genotypes bred under intensive management practices may not be able to benefit fully from soil health promoting practices if they have lost their ability to effectively interact with key soil organisms. The purpose of this study was to explore this idea by studying how spring wheat genotypes with different breeding contexts and histories respond to improved soil health achieved via additions of organic matter and soil fauna. A greenhouse experiment with a full factorial complete randomized design was carried out at Colorado State University, Fort Collins, between June and November, 2016. The treatment factors included spring wheat genotype, as well as compost and earthworm additions. The genotypes included a wild ancestor of wheat, Aegilops tauschii, two older genotypes of spring wheat, Gypsum and Red Fife, and two near-isogenic modern genotypes, Scholar Rht2M and Scholar Rht2W, that differ only by the presence of the semi-dwarf allele Rht-D1b in ScholarRht2M. Each wheat genotype was grown in rootboxes (24.5 x 3.5 x 38.0 cm) that received either soils amended with composted manure or not, and with or without the addition of earthworms (two Aporrectodea caliginosa per box). Measurements included plant growth (heading date, number of tillers), biomass (aboveground and root biomass, root:shoot ratio), root morphology (root length and diameter), yield-related traits (number of seeds, seeds weight, average weight per seed, harvest index), nitrogen content (vegetative aboveground and grains), and nitrogen uptake. Findings indicate that interactions between genotypes and soil treatments were inconsistent, and the original hypothesis, that older wheat genotypes would show a greater response to improved soil biological conditions relative to newer genotypes, was not well supported. Overall, the aboveground and yield responses to compost were small compared to the root responses. Composted manure additions, increased root length, biomass, and diameter only in the wild accession (Ae. tauschii) and older Gypsum wheat variety. Modern genotypes, on the other hand, exhibited little root trait plasticity except in root diameter, which decreased with compost additions. Except for a decrease observed in Red Fife, compost effects on aboveground biomass were not significant for most genotypes. Genotype x earthworm interactions were only observed in the vegetative biomass N uptake, and earthworm effects in general were low due to low survival of the earthworms. Ae. tauschii and Gypsum had a more positive response to compost addition for both aboveground and root biomass, indicating that these genotypes may better take advantage of soil health promoting practices. While Gypsum had a similar response to the wild accession when compost was added, Red Fife tended to respond more like the modern genotypes. Overall, my findings suggest that different wheat genotypes can respond distinctly to changes in soil management and biological activity. Only a few genotypes were tested, but a number of clear genotype x soil biology interactions highlights the importance of considering soil management practices, environmental context, and breeding history for different wheat lines, so that we can better manage plant x soil interactions.
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    Hydrologic comparison of prescriptive and water balance covers
    (Colorado State University. Libraries, 2018) Stock, Caleb Swenson, author; Bareither, Christopher A., advisor; Scalia, Joseph, IV, committee member; Paschke, Mark W., committee member
    The objective of this study was to compare the water balance of prescriptive and water balance cover (WBC) designs for Larimer County Landfill (LCL) via hydrologic modeling. A prescriptive cover is designed to limit percolation into underlying waste via a low permeability layer, whereas a WBC is designed to limit percolation via storing infiltrated precipitation and subsequently releasing the water through evaporation and transpiration. Guidance on WBC designs in Colorado are based on geographical location of the site and particle-size distribution of the available cover soils. Soil characteristics and engineering properties were determined from exhumed samples for a completed closure phase of LCL (Phase 1) and two borrow areas (Borrow Area 3 and Borrow Area 4). Hydrologic modeling was completed using VADOSE/W to predict the percolation rate through the prescriptive and water balance covers. The wettest ten consecutive years on record with a sufficiently complete meteorological data set (1992-2002) were selected for the analysis. Vegetation parameters were assigned to represent the revegetated state observed in Phase 1 and the natural conditions observed in the borrow areas. Predicted percolation through a prescriptive cover was < 0.1 to 2.2 mm/yr, depending on assumed saturated hydraulic conductivity. Evaporation was the primary process for removing water from the prescriptive cover models. Predicted percolation through the WBC models ranged from 6.3 to 11.3 mm/yr depending on the borrow area soil and vegetation parameters. Transpiration was the primary process for removing water from the WBC models. Within all of the regulatory acceptable cover models' evapotranspiration removed 94 to 102% of the precipitation received during the ten years modeled. Results of this study indicate that either a prescriptive cover with a total thickness of 106.7 cm (3.5 ft) or a WBC with a thickness of 76.2 cm (2.5 ft) will meet regulations for final closure cover at LCL.
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    Pile burn scar restoration at Lily Lake: tradeoffs between abundance of non-native and native species
    (Colorado State University. Libraries, 2019) Sexton, Ian C., author; Brown, Cynthia S., advisor; Fornwalt, Paula J., committee member; Paschke, Mark W., committee member
    Accumulation of fuels in forests across the western United States is producing larger and more severe wildfires. To decrease wildfire severity and increase forest resilience, foresters regularly remove excess fuel by burning woody material in piles. This common practice can also cause persistent ecosystem changes that include alteration of soil physical and chemical properties due to extreme soil heating, which can favor invasion by non-native plant species. Abundance and species richness of native plant communities may also remain depressed for many years after burning has removed vegetation and diminished propagules in the soil. This adds to the vulnerability of burned areas, which can transition to dominance by invasive species. Research into the use of revegetation techniques following pile burning to suppress invasion is limited. Studies conducted in various woodland types that investigated revegetation of pile burn scars have met with varying success. To assess the effectiveness of restoring pile burn scars in Rocky Mountain National Park, Colorado, we monitored vegetation in 26 scars at Lily Lake the growing season after burning. Later that summer we selected 14 scars for restoration that included soil scarification, seed addition, and pine duff mulch cover. We monitored the scars for 3 years following restoration and found that cover of seeded species exceeded surrounding unburned areas. This suppressed cover of non-native species as well as native species that were not seeded during restoration relative to controls. Productivity of a native forb planted as seed in scars 3 years after restoration was depressed relative to unrestored scars. We conclude that restoration of pile burn scars can be a useful management tool that will likely need to be part of an integrated pest management program addressing preexisting infestations near scars. Monitoring for periods longer than 3 years will help us understand how long suppression of native and non-native species by restoration species may persist.
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    The application of ecological principles to accelerate reclamation of well pad sites
    (Colorado State University. Libraries, 2009) Eldridge, Joshua David, author; Redente, Edward F., advisor; Barbarick, Kenneth A., committee member; Paschke, Mark W., committee member
    Western Colorado is experiencing a boom in natural gas development. However, the semi-arid ecosystems of this area have difficulty recovering from energy related disturbances. The purpose of this study was to improve reclamation techniques of natural gas well pads on the Western Slope of Colorado to establish viable native plant populations. The reclamation techniques studied are intended to repair damaged ecological processes and help guide the trajectory of natural plant succession toward a more desired plant community. The study examined the effects and interactions of seedbed preparation, soil amendments, seed mixtures, and seeding methods. The experiment was conducted in pinyon-juniper and sagebrush steppe/salt desert scrub plant communities on five natural gas well pads near Parachute, Colorado. Soil and plant cover data were collected to assess the effectiveness of 16 different treatment combinations. The data were analyzed by using a generalized linear mixed model. There was a significant difference in precipitation between 2007 and 2008, with 2007 receiving only 53% of average precipitation while 2008 was slightly above the average precipitation of 300 mm. After two growing seasons, the data show that the use of wood chips as a soil amendment increased organic matter content and reduced non-native species. Rough seedbed preparation increased the establishment of native species, especially during years of below average precipitation. Island broadcasting resulted in an increase of noxious plant cover in 2008. Additional monitoring over time is still needed before more conclusive statements can be made about the effects of the different seed mixtures. Soil testing revealed that soil salinity will need to be ameliorated in some areas for successful reclamation to occur.