Browsing by Author "Meiman, Paul J., advisor"
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Item Open Access Canada thistle (Cirsium arvense [L.] Scop.) response to mowing, herbicide, competitive grasses, and soil amendments on wetland, upland, and mesic sites(Colorado State University. Libraries, 2009) Knudson, Julie A., author; Redente, Edward F., advisor; Meiman, Paul J., advisorCanada thistle (Cirsium arvense [L.] Scop.) is one of the most problematic weeds of temperate regions and is found throughout North America, Europe, Africa, and across central Asia. Canada thistle's ability to spread quickly and recover from many control methods makes managing Canada thistle a significant challenge for land managers. Herbicide application can be effective, but mixed results, toxicity concerns, and the need for re-application demand new, more efficient strategies that reduce herbicide use. A greenhouse study tested effectiveness of clipping and grass seeding for Canada thistle control. Grasses used included two natives (western wheatgrass [Pascopyrum smithii {Rydb.} A. Löve], streambank wheatgrass [Elymus lanceolatus {Scribn. & J.G. Sm.} Gould ssp. lanceolatus]) and one sterile hybrid (common wheat [Triticum aestivum L.] x tall wheatgrass [Thinopyrum ponticum {Podp.} Z.W. Liu & R.C. Wang]) called Regreenâ„¢. Grasses were seeded alone or in combination (Regreen+western wheatgrass) in pots with Canada thistle. Field Study I tested combinations of mowing, herbicide, and grass seeding across two habitats (wetland, upland) and three different local climatic regimes for control of Canada thistle. Grass treatments involved seeding western wheatgrass (upland sites) or prairie cordgrass (Spartina pectinata Bosc ex Link) (wetland sites) alone or in combination with Regreen (upland and wetland sites). Six sites (three wetland, three upland) were paired geographically across Colorado with each wetland site in close proximity to an upland site. Field Study II tested combinations of mowing, herbicide, soil amendment addition (organic matter, manganese), and grass seeding (western wheatgrass, intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] on a Colorado mesic site. In greenhouse trials, clipping inhibited Canada thistle growth, while grass seeding did not. In Field Study I, herbicide application produced effective control. In Field Study II, tilling enhanced herbicide effectiveness. Organic matter or manganese alone did not reduce Canada thistle growth. Manganese addition reduced herbicide effectiveness. In both field studies, neither mowing nor grass seeding enhanced herbicide effectiveness, and tilling did not increase Canada thistle biomass. Future research should address restoration of infested wetland sites, the importance of irrigation during drought for restoration, and the mechanism through which manganese sulfate inhibits herbicide effectiveness.Item Open Access Characteristics of hummocks and hummocked wetlands in Colorado(Colorado State University. Libraries, 2011) Smith, Mae, author; Meiman, Paul J., advisor; Brummer, Joe E., committee member; Cooper, David J. (David Jonathan), 1952-, committee memberThere is considerable uncertainty regarding mechanisms of hummock formation. The first step in assessing hummocks in Colorado was to compare the characteristics associated with hummocked and non-hummocked sites. To do this, site characteristics of hummocked and non-hummocked riparian areas and wetlands across Colorado were sampled. Two site characteristics were positively related, and three site characteristics were negatively related to hummock occurrence. Three groups of hummocked wetlands with distinct morphological, vegetative and climatic characteristics were identified. A finer-scale approach was then used to examine mechanisms of hummock formation. Four hummocked sites in north-central Colorado were selected for detailed research. Soil temperature regimes and presence of water in interspaces were evaluated to determine whether or not conditions described in the most widely accepted theories of hummock formation occurred. Hummock/interspace pairs were instrumented with soil temperature sensors and water level indicators. Results indicate that there were sufficient air freeze-thaw cycles to support hummock formation by needle ice. Conditions supporting differential frost heave through ice lensing were also documented. Numerous temperature differentials were detected between the hummock top, hummock base and interspace creating temperature gradients that could lead to hummock formation by differential frost heave. The final step was to evaluate soil and vegetation characteristics of hummocks and interspaces with respect to hummock formation theories based on differential frost heave and plant biomass accumulation. Soil cores were collected from hummocks and interspaces to evaluate soil horizon orientation and thickness of the surface organic horizon. Bulk density, vegetation cover and herbaceous biomass production were also determined. Bent soil horizons indicative of differential frost heave were observed in four hummock/interspace pairs. The organic horizon was thicker and bulk density was lower in the hummocks compared to interspaces but the amount of organic matter in the two positions was similar. Accumulation of plant biomass may lead to increased hummock height. The finer-scale study revealed evidence supporting multiple mechanisms of hummock formation and development. These mechanisms may form different hummock types which is consistent with the findings of the larger-scale study.Item Open Access 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 memberLarkspurs (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.Item Open Access Riparian area invasive plant management along the Niobrara River, targeting yellow flag iris (Iris pseudacorus L.)(Colorado State University. Libraries, 2016) Spaak, Jordan L., author; Meiman, Paul J., advisor; Beck, K. George, committee member; Ocheltree, Troy, committee memberYellow Flag Iris (YFI) (Iris pseudacorus L.) is an invasive exotic species that is causing substantial changes to the ecology of the Niobrara River and the adjacent riparian area habitat. Options for invasive plant management along the Niobrara River, like most riparian wetlands, are quite limited. Currently, herbicides offer the best opportunities for successful YFI management in riparian habitats such as those along the Niobrara River but irrigation diversion and livestock grazing are prevalent which impose further limitations on management options. In this study, we analyzed the efficacy of multiple potential YFI management methods, including; chemical (glyphosate), mechanical (cutting), plant competition, and trampling. A combination of field and greenhouse studies were used. Field studies were conducted at Agate Fossils Beds National Monument, Harrison Nebraska, U.S.A. and greenhouse experiments were completed at Colorado State University, Fort Collins, Colorado, U.S.A. The greenhouse studies were conducted to determine how temperature, light, seed scarification, and trampling, affected germination, seedling growth and survival of YFI. The field studies focused on the effectiveness of glyphosate, cutting, planting native plants, and trampling on YFI. Results from field studies indicate that cutting established plants stimulates YFI growth, spring application of glyphosate resulted in a short-term reduction of YFI abundance, and planting native plants did not reduce YFI abundance. Findings indicate that YFI prefer shaded areas and cooler temperatures for emergence and warmer shaded areas for growth. Seed scarification did not affect emergence. Trampling in the field reduced YFI density by 75% and plant height by 58%. Simulated trampling that targeted the plant crown and 1-2-cm above the crown reduced survival, though trampling that targeted the crown was five times more likely to kill the plant than trampling 1-2-cm above the crown.Item Open Access The skill of managers and the wisdom of herds: examining an alternative approach to grazing management in larkspur habitat(Colorado State University. Libraries, 2019) Jablonski, Kevin E., author; Meiman, Paul J., advisor; Boone, Randall B., committee member; Fernández-Giménez, MarÃa E., committee member; Ocheltree, Troy W., committee memberThe many species of larkspur (Delphinium spp. L.) are among the most dangerous poisonous plants on rangelands in the western United States, causing death losses estimated at 2-5% (up to 15%) per year for cattle grazing in larkspur habitat. Research has estimated the value of these losses at $234 million per year. Other effects, such as altered grazing management practices and consequent lost forage quantity and quality, are significant but poorly understood. Current best management practice recommendations stress seasonal avoidance of pastures with larkspur present, with little evidence that this is practical or ultimately effective. Alternative approaches to addressing this complex challenge are difficult to design, test, and apply due to the threat of dead livestock. In this dissertation I explore an alternative approach based on the idea that it may be possible to manage cattle grazing such that no individual consumes a lethal dose, regardless of timing of grazing or larkspur density. This idea was inspired by producers past and present who have reported such success. I examine this hypothesis using agent-based models and a field experiment with Geyer's larkspur (D. geyeri Greene), the focal species throughout this research. Chapter 2 presents a conceptual model that situates this work within the broader context of livestock grazing management and rangeland science. This synthesis also highlights the potential for conceptual models to aid in the design, application, communication, and consilience of research in rangelands. Drawing on a wide range of work, this model challenges the discipline of rangeland science to integrate a broader array of methods and epistemologies to create knowledge sufficient to the complexity of the systems under study. Agent-based models (ABMs) provide an effective method of testing alternate management strategies without risk to livestock. ABMs are especially useful for modeling complex systems such as livestock grazing management and allow for realistic bottom-up encoding of cattle behavior. In Chapter 3, I introduce a spatially-explicit, behavior-based ABM of cattle grazing in a pasture with a dangerous amount of D. geyeri. This model tests the role of herd cohesion and stocking density in larkspur intake, finds that both are key drivers of larkspur-induced toxicosis, and indicates that alteration of these factors within realistic bounds can mitigate risk. Crucially, the model points to herd cohesion, which has received little attention in the discipline, as playing an important role in reducing lethal acute toxicosis. As the first agent-based model to simulate grazing behavior at realistic scales, this study also demonstrates the tremendous potential of ABMs to illuminate grazing management dynamics, including fundamental aspects of livestock behavior amidst ecological heterogeneity. Chapter 3 raises the question of the potential response of larkspur to being grazed. In Chapter 4, I examine the response of D. geyeri to two seasons of 25% or 75% aboveground plant mass removal. The 75% treatment led to significantly lower alkaloid concentrations (mg•g-1) and pools (mg per plant), while the 25% treatment had a lesser effect. Combined with lessons from previous studies, this indicates that Geyer's larkspur plants subject to aboveground mass removal such as may occur via grazing can be expected to become significantly less dangerous to cattle. We suggest that the mechanisms for this reduction are both alkaloid removal and reduced belowground root mass, as significant evidence indicates that alkaloids are synthesized and stored in the roots. The most common explanations for the evolution and persistence of herd behavior in large herbivores relate to decreased risk of predation. However, poisonous plants such as larkspur can present a threat comparable to predation. Chapters 3 and 4 point to the cattle herd itself as the potential solution to this seemingly intractable challenge and suggest that larkspur and forage patchiness may drive deaths. In Chapter 5, I present an agent-based model that incorporates neutral landscape models to assess the interaction between plant patchiness and herd behavior within the context of poisonous plants as predator and cattle as prey. The simulation results indicate that larkspur patchiness is indeed a driver of toxicosis and that highly cohesive herds can greatly reduce the risk of death in even the most dangerous circumstances. By placing the results in context with existing theories about the utility of herds, I demonstrate that grouping in large herbivores can be an adaptive response to patchily distributed poisonous plants. Lastly, the results hold significant management-relevant insight, both for cattle producers managing grazing in larkspur habitat and in general as a call to reconsider the manifold benefits of herd behavior among domestic herbivores. The findings in this dissertation build a strong case for an alternative approach to grazing management in larkspur habitat but fall short of actionable recommendations. For one, this is because a one-size-fits-all solution that would work across the great diversity of habitats and management systems in which larkspur is found is unlikely. Instead, these findings must be placed in context with existing knowledge and the complex multiscale decision-making processes of producers. Future work will thus focus on improving our understanding of the diverse set of management circumstances under which the many species of problematic larkspur are found.Item Open Access Trampling by cattle negatively impacts invasive yellow-flag iris (Iris pseudacorus) under flooded conditions(Colorado State University. Libraries, 2020) Stoneburner, Alexandra L., author; Meiman, Paul J., advisor; Ocheltree, Troy W., advisor; Nissen, Scott, committee memberYellow-Flag Iris (Iris pseudacorus L.) is a non-native, invasive wetland plant in North America that disrupts riparian ecosystem processes. Due to its physiological and morphological characteristics, I. pseudacorus has the capacity to exclude native vegetation and form extensive monocultures in both lotic and lentic wetland systems. Methods commonly used to manage I. pseudacorus infestations include manual and mechanical treatments for small populations and chemical treatment for larger populations. While these management techniques are often effective, options can be restricted by the biotic and abiotic conditions of a given site. For example, there are situations where chemical treatments near waterways (i.e. close to irrigation water diversions) may be prohibited due to label restrictions. The objective of this research was to evaluate the effectiveness of cattle trampling for reducing I. pseudacorus prevalence in riparian habitats. A field study was established on a ranch in northwest Nebraska to evaluate cattle trampling effects on I. pseudacorus density and height after two consecutive years of treatment. In a complementary greenhouse study, the effects of inundation and two different timings of simulated trampling on I. pseudacorus density, height, and rhizome stress (as measured by soluble sugar concentration) were also evaluated. No statistical differences in soluble sugar concentrations were observed among treatments; however, these data suggest that cattle trampling will reduce I. pseudacorus density and height at both timings, but trampling plus inundation was the most effective treatment combination.Item Open Access Understory community dynamics ten years after a mixed-severity wildfire in ponderosa pine and aspen stands in the Black Hills of South Dakota, USA(Colorado State University. Libraries, 2012) Hirsch, Mandi L., author; Meiman, Paul J., advisor; Shepperd, Wayne D., committee member; Brummer, Joe E., committee memberWildfires are important disturbances due to their ability to influence many ecosystem processes and functions. Following a mixed-severity wildfire, understory vegetation composition and structure may undergo both long- and short-term changes because of modified growing conditions, removal of overstory competition and changes in the amounts of available resources. While more rapid, short-term changes are easily observed and documented, understanding long-term changes is of critical importance for management purposes and allowing professionals to gain insights into forest composition following a major disturbance. Late in the summer of 2000, 34,000 ha of ponderosa pine (Pinus ponderosa Lawson & C. Lawson) forests in the Black Hills of South Dakota burned in what is now called the Jasper Fire; the largest wildfire recorded in the state's history. The Jasper Fire was classified as a mixed-severity wildfire resulting in a mosaic of areas burned at low- (25%), moderate- (48%) and high-severity (27%). Following the fire, plant communities appeared to recover rapidly leading to questions regarding how long various postfire communities would persist, how postfire community development varied by fire severity, and differences observed between zones of the Jasper Fire. Ultimately, many were interested in long-term postfire community dynamics. In this study we examined the understory vegetation composition and structure (relative abundance of graminoids, forbs and shrubs) and frequency of invasive species relative to fire severity (unburned, low, moderate and high) and zone (northern, central and southern) in ponderosa pine and aspen (Populus tremuloides Michx.) stands 10 years after the Jasper Fire in the Black Hills of South Dakota, USA. In both ponderosa pine and aspen sites, understory community composition differed by zone and severity simultaneously. In ponderosa pine stands, canopy cover of four species varied by only zone or severity and eleven varied by zone and severity simultaneously. In aspen stands, canopy cover of two species varied only by zone or severity and canopy cover of three species varied by zone and severity simultaneously. Grass and shrub cover were explained by the interaction of zone and severity in ponderosa pine stands while cover of forbs varied by zone and severity but not their interaction. In aspen stands grass, forb and shrub cover all varied by zone and severity simultaneously. Grass and forb cover values 10 years postfire were similar to the 5 year postfire levels, and were greatest in moderate and high-severity burned areas. Shrub cover was also similar 5 and 10 years postfire, with lower values in burned areas driven by the loss of common juniper (Juniperus communis L.). Although common juniper cover was drastically decreased by fire, other shrubs are beginning to appear across the landscape. Total plant cover appeared to be lower 10 years postfire than compared to 5 years postfire which might be driven by a shift from annual and biennial plants to perennial plants. Frequencies of invasive species reached 60-70%, however, canopy cover of individual invasive species never exceeded 5% in either ponderosa pine or aspen stands. Ten years postfire, burned areas support understory plant communities dominated by native perennial plants with very few invasive exotic species. Post-fire rehabilitation efforts need to be designed on a site-specific basis and invasive species monitoring should continue to ensure that these plants do not become a concern in the future.