Theses and Dissertations

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Open Access
Pastoral development in the Sahel
(Colorado State University. Libraries, 1980-03) Greenwood, Gregory Boyce, author; Bartlett, E. T., advisor; Alers-Montalvo, Manuel, committee member; Wasser, Clinton, committee member
Ecological, geographic, economic and anthropological literature pertaining to the Sahel is reviewed in order to provide a basis for pastoral development policy. Great variability in annual primary production is the principal characteristic of Sahelian vegetation. The range can best be improved by increasing the density of woody plants on dry season range. Simple grazing trials are recommended to verify and quantify this improvement. Traditional pastoral systems were found to be well adapted to the great variability of the Sahel. Traditional strategies sought to obtain a consummable output while maintaining a level of risk aversion. The role of commercialization in an optimal strategy is unclear and may depend on the pastoralist's wealth, personal discount rate, perception of future risk and perception of his herd as a risk averting mechanism. Historical events have increased pressure on the resource base while disrupting the traditional social and political structures of the Sahel. Resource degradation and increased household insecurity have resulted. Development projects must change the micro-economic environment of the pastoralist by simultaneously increasing primary production and decreasing risk. A number of ecological and social techniques are discussed. A new type of rural institution is proposed that would unite pastoralists, local government officials and technical experts in developing, testing and evaluating potential solutions.
Open Access
Interaction between light, nitrogen and mycorrhizal fungi on photosynthesis of ectomycorrhizal pine
(Colorado State University. Libraries, 1983) Ekwebelam, Sebastian A., author; Reid, C. P. P., advisor; Doxtader, Kenneth G., committee member; Wallner, Stephen J., committee member; Hunt, H. William, committee member
The importance of mycorrhizae to the physiological functions of plants is relatively well documented. Despite the obvious benefits of mycorrhizae for the enhancement of seedling growth, study of the relationship between applied cultural practices, such as shading, fertilization and mycorrhizae formation, and growth and photosynthesis of containerized nursery stock has been limited. The long-term objective of the present study, therefore, was to gain a more complete understanding of how the aggregate factors of light, nitrogen fertilization and mycorrhizae formation influence growth and photosynthesis of containerized seedlings, aimed at optimizing seedling production in a nursery environment. Seedlings of lodgepole pine (Pinus contorta Dougl.) were grown for 16 weeks without ectomycorrhizae in the greenhouse at 3 level s of irradiance (high, medium and low) by use of shadecloth, and ammonium nitrate (3, 62 and 248 ppm N) . Measurements at 5, 10 and 16 weeks of age indicated that biomass increased significantly with increasing levels of irradiance and nitrogen over the ranges studied. Although root/shoot ratios increased from low to high irradiance at each harvest, nitrogen application resulted in increased ratios from 3 to 62 ppm N, but decreased ratios at 248 ppm N. Nitrogen and phosphorus concentration generally decreased with increase in irradiance, but total N content and photosynthesis per unit leaf area generally increased from low to high levels of both irradiance and nitrogen. In a mycorrhizal fungi inoculation study, lodgepole pine seedlings were grown for 10 weeks without ectomycorrhizae at the aforementioned 3 levels of irradiance and nitrogen. At 10 weeks, mycorrhizal treatments, inoculation with either Pisolithus tinctorius or Suillus granulatus, were superimposed on the light and nitrogen treatments, and the seedlings were grown for an additional 6 weeks. Mycorrhizae formation increased with increase in irradiance, while fertilization with 62 ppm N resulted in greater mycorrhizae formation than either 3 or 248 ppm N. Further, inoculated plants had significantly greater biomass and nutrient contents than nonmycorrhizal seedlings. Inoculation with P. tinctorius and granulatus resulted in photosynthetic rates, 1.87 and 1.85 mg CO2dm-2h-1, respectively, significantly greater than nonmycorrhizal plants (1.41 mg CO2dm-2h-1). Although the increase in growth of the mycorrhizal seedlings was associated with increased photosynthesis, the magnitude of this response depended on specific combinations of irradiance and nitrogen fertilization. These results emphasize the importance of the interactions among irradiance, nitro gen fertilization, and mycorrhizae development in the growth of containerized seedlings.
Open Access
Effects of bovine urinary nitrogen on the nitrogen cycle of a shortgrass prairie
(Colorado State University. Libraries, 1983) Stillwell, Mark A., author; Woodmansee, Robert G., advisor; Rittenhouse, Larry R., committee member; Parton, William J., committee member; Porter, Lynn K., committee member
Free grazing ungulates were hypothesized to exert a significant influence on the nitrogen cycle of a grazed shortgrass prairie ecosystem. Two field studies were performed from May 1980 through March 1982 in shortgrass prairie pastures at the Central Plains Experimental Range northeast of Fort Collins, Colorado. The objective of the first study was to quantify seasonal variation in nitrogen ingested by free grazing heifers and the partitioning of the ingested nitrogen among urine, feces, and storage in animal bodies. A herd of eight yearling heifers in a 125 ha. pasture consumed 116 kg of forage nitrogen during the growing season and 91 kg of forage nitrogen during the dormant season. This was only 10% of peak standing crop of forage nitrogen. Ten percent of the nitrogen ingested during the study period was incorporated into body growth. Excreted nitrogen was partitioned between urine and feces at 54% and 46% for the growing season and 45% and 55% for the dormant season. This was a deposition rate of 1.6 kg N/ ha. for the pasture. The objective of the second field study was to determine the fate of urinary nitrogen once it was returned to various soils in a pasture. Simulated urine with l5N labeled urea was added at the rate of 45 g/m² to the soil at three sites on a catena. Urea hydrolysis was rapid at all sites with little urea remaining after four days. Over a 15 month period a sandy ridgetop and a clay swale soil retained about 70% of the added nitrogen. Only 40% was recovered from a midslope soil. Elevated calcium levels in the ridgetop and high clay content in the swale soil were important in the conservation of nitrogen. Cattle grazing was shown to be important in the N cycle by processing 10% of the standing N and depositing it in concentrated spots on the soil. Long term effects indicate that up to 50% of a community may be affected at any time.
Open Access
Gap-phase dynamics and succession in the shortgrass steppe
(Colorado State University. Libraries, 1988) Coffin, Debra P., author; Lauenroth, William K., advisor; Redente, Edward F., committee member; Woodmansee, Robert George, committee member; Kirchner, Thomas B., committee member
Previous conceptualizations of succession in shortgrass plant communities have focused on the effects of large-scale disturbances with the conclusion that the dominant plant species, blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] fails to recover after a disturbance. My overall objective was to apply a gap dynamics approach based on small, frequently-occurring disturbances to shortgrass plant communities with the hypothesis that the death of a fullsize B. gracilis plant results in a gap in the belowground resource space and initiates the successional processes of gap dynamics. I concluded that a gap dynamics conceptualization of shortgrass communities provides a promising alternative to a conceptual model that emphasizes the effects of large disturbances. My first objective was to evaluate the effects of three small, patch-producing disturbances (cattle fecal pats, western harvester ant mounds, and small animal burrows) on B. gracilis-dominated plant communities by developing a spatially-explicit simulation model. Propagating the effects of these disturbances through time suggested that B. gracilis is able to recover after small disturbances. My second objective was to evaluate the short-term successional dynamics on small disturbances. I conducted a field study to evaluate the effects of three types of disturbances and their associated characteristics of size, seasonality, and location by soil texture on the recovery of plants. The density and cover of plants on the two naturally-occurring disturbances (western harvester ant mounds and small animal burrows) were dominated by perennials one year after the disturbances occurred while the majority of the cover on the artificially-produced disturbances was attributed to annuals. My third objective was to evaluate the long-term successional dynamics on small disturbances and the time required for B. gracilis to recover after a disturbance. I developed a gap dynamics simulation model based on the belowground gap in the resource space that results when an individual B. gracilis plant dies. The faster recovery time of B. gracilis in the model than observed experimentally on large disturbances suggests that processes associated with the recovery of B. gracilis may be scale-dependent.
Open Access
Three-dimensional finite element model to predict pole strength
(Colorado State University. Libraries, 1992) Franco, Nilson, author; Pellicane, Patrick A., advisor; Bodig, Jozsef, committee member; Criswell, Marvin E., committee member; Shuler, Craig E., committee member
A three-dimensional finite element model was used to predict the strength and location of failure of nine wood transmission poles. The poles were made from three commonly used species (western red cedar, Douglas-fir and southern pine) in North America. All poles were tested to failure as a cantilever beam with a concentrated load applied to the tip. The methodology involved was to select several eighteen inches long segments, located along the poles, which contained the most severe defects such as cluster of knots, spiral grain, including material inhomogeneity in the highly stressed region. Each segment was analyzed using the finite element technique with appropriate boundary conditions. Material properties for each segment were determined by measuring clear-wood elastic and strength parameters in boles taken from broken poles. The information about knots and spiral grain, obtained by visual inspection of the pole surface, was used to identify the worst knot clusters and grain deviation in any segment. Knots were modeled in the finite element mesh and the localized grain deviation around the knots were determined through the use of the flow-grain analogy model. Finite element computer analysis were performed through the use of the program GTSTRUDL. The model resulted in a total of 288 three-dimensional, isoparametric, linear strain, 20-node parallelopiped and 15-node wedge shaped elements. For the nine poles studied, the results showed good agreement between predicted and experimental strength. The predicted values for strength differed from the actual ones with an average deviation of 7% (below the actual). Concerning failure location, in six of the poles, failure was verified in the same places as those predicted by the model. In the three other cases the failure with the maximum error of three feet, except for one pole where the deviation was twelve feet. The study revealed that the three-dimensional finite element approach to model growth characteristics applied to the more critical segments along the pole length proved to be very useful tool for strength and failure location prediction of poles.
Open Access
Effects of cultivation and recovery on soil organic matter and N mineralization in shortgrass steppe
(Colorado State University. Libraries, 1993) Ihori, Tamiko, author; Burke, Ingrid C., advisor; Binkley, Dan, committee member; Lauenroth, William K., committee member; Coffin, Debra P., committee member
Understanding cultivation effects on soil organic matter (SOM) and available nutrients to plants is important, because SOM is an important storage of C globally and available nutrients are an important factor in plant growth. It is also important to understand recovery from disturbance such as cultivation. I conducted two studies: one on total SOM and the other on in situ N mineralization in native, cultivated, and recovering abandoned fields in the shortgrass steppe of northeastern Colorado. I examined total C and N content in 30 cm depth soil of native fields, abandoned fields that were historically cultivated and then abandoned about 50 years ago, and cultivated fields that were cultivated more than 50 years, at 13 sites in the Pawnee National Grasslands. Both total C and N were highest in native, intermediate in abandoned, and lowest in cultivated fields. An average loss from cultivation for total C was 26% and for total N was 29%. Precipitation had a significant effect on SOM content in native fields, but did not have an effect on C and N losses from cultivation. C/N ratio differences among native, abandoned, and cultivated fields were not significant in 30cm depth soil. I estimated recovery of SOM using the CENTURY model. During 50 years of abandonment of lands, I estimate that 25 g/m² of C has recovered, but we could not detect N recovery. In situ net mineralization in 15 cm depth soil was also examined among three land management treatments (native, abandoned, and cultivated) and two microsites (under individual Bouteloua gracilis plants and between individual plants). Total C, N, and C/N ratios were highest in native, intermediate in abandoned, and lowest in cultivated fields, and higher under plants than between plants. In situ net N mineralization, % N mineralization, and moisture content in soils were highest in cultivated fields, but there was no difference between native and abandoned fields. In situ net N mineralization, % N mineralized, and soil moisture content were not significantly different between microsites. A ratio of field net N mineralization to lab net mineralization was highest in cultivated fields, but differences between native and abandoned fields were not significant. This ratio tended to be higher between plants than under plants, but there was not a significant difference. Because this ratio may be an index of environmental limitation to N mineralization, I infer that cultivated fields and between plant locations have less environmental restriction than native fields or underplant locations. I concluded from these results that nitrogen availability to plants is recovered in abandoned fields from the results of in situ N mineralization. However total C has recovered only 25 g/m², and total N did not show recovery in abandoned fields.
Open Access
Plant species effects on soil organic matter turnover and nutrient release in forests and grasslands
(Colorado State University. Libraries, 1996) Scott, Neal Arthur, author; Binkley, Dan, advisor; Burke, Indy, committee member; Lauenroth, Bill, Ryan, Michael, committee member
Although feedbacks between plant species and ecosystem dynamics have been demonstrated in a variety of terrestrial ecosystems, little research has examined the mechanistic relationship between plant species characteristics, the formation and turnover of soil carbon and nitrogen pools, and ecosystem processes such as net N mineralization. My objective was to examine two possible effects of species on soil C and N dynamics; changes in organic matter quality and changes in soil aggregation. For several forest ecosystems, litter lignin:N ratio correlated negatively (non-linear) with net N mineralization, but the relationship did not apply to grass species. Climatic factors (temperature, precipitation) explained little of the variation in net N mineralization. The relationship between litter lignin:N ratio and net N mineralization from mineral soil and the forest floor was similar, suggesting that plant litter quality affects both forest floor and mineral soil organic matter quality. For tree species monocultures in Wisconsin, net N mineralization during 387 day laboratory incubations indicated that species alter the quality of readily decomposable pools of soil N, and have little effect on more recalcitrant soil N. Changes in the quality of soil N correlated positively with in situ net N mineralization. Grass species did not influence N mineralization. Neither grass nor tree species influenced soil C dynamics, but differences in soil characteristics between sites influenced soil C dynamics. Soil microbes appear to act as a “decay filter”, converting heterogeneous plant material into relatively homogeneous soil humus. Changes in soil aggregate size distribution should alter whole-soil C and N quality because different size aggregates contain organic matter of different quality. Although tree species slightly altered aggregate size distribution, aggregate size distribution related poorly to whole-soil C and net N mineralization. Tree species had no effect on the physical protection of organic matter in soil aggregates or on organic matter quality of different size aggregates. Species characteristics had little effect on soil C mineralization, but species-related changes in the quality of readily decomposable soil N pools (not the pool size) influenced net N mineralization. This suggests that the feedbacks between plant species and soil N cycling occur rapidly, ensuring an adequate nutrient supply when plant community structure changes.
Open Access
Organization and management of natural resources and environmental research
(Colorado State University. Libraries, 1998) Van Haveren, Bruce P., author; Woodmansee, Bob, advisor; Child, Dennis, committee member; Dyer, Al, committee member; Hautaluoma, Jack, committee member; Lawrence, Bob, committee member
The organization and management of research lacks a unifying theoretical foundation. A post-reformative theory of research management is based on six cornerstones: 1) the research enterprise consists of multiple dimensions and this multiformity is potentially synergistic; 2) knowledge is gained incrementally throughout the research process; 3) research is a form of societal investment possessing both risks and potential gains; 4) research organizations are inherently self-organizing and dynamic; 5) research is increasingly pluralistic and heterogeneous; and 6) research evaluations must focus on processes, outcomes, or overall effectiveness, in terms of both intrascientific and extra scientific contributions. Based on observations of 14 environmental research groups at six environmental research laboratories, group research organizes naturally and informally in environmental research settings primarily because of the interdisciplinary nature of environmental research. Groups were not necessarily identifiable in organizational charts. Often they were spontaneously occurring dyads or clusters of individuals with similar interests or interdependent skills. A formal division and branch structure hinders group research because of fiefdom attitudes of branch chiefs. Epistemological differences exist within research groups and may present obstacles or result in dysfunctional groups. Research groups must spend considerable time on problem definition, problem analysis. Working towards a group goal, and developing a common system of inquiry. Perceived performance did not correlate well with measured performance. If perceived performance is a part of research evaluation, perceptions of performance must be specific as to performance criteria. For the research groups studied, member-perceived publication quality was not well correlated with measured publication quality. Director-perceived performance did not reflect measured performance. Goal congruence between group leaders and members was high in the case of the fourteen research groups. However, communication about expectations and performance broke down between laboratory directors and research groups. The dynamic constellation, an organizational model stressing a flexible, organic, group oriented structure and integrator and boundary-spanner roles, is recommended for natural resource and environmental research organizations. A multidimensional research portfolios suggested as a management approach. Managing research portfolios in a pluralistic and heterogeneous environment involves a large number of essential tensions, but these tensions also become an effective management tool.
Open Access
Alkaline/peracetic acid as a pretreatment of lignocellulosic biomass for ethanol fuel production
(Colorado State University. Libraries, 1998) Teixeira, Lincoln Cambraia, author; Crews, Donald L., advisor; Schroeder, Herbert A., committee member; Linden, James C., committee member; Wangaard, Frederick F., committee member
Peracetic add is a lignin oxidation pretreatment with low energy input by which biomass can be treated in a silo type system for improving enzymatic digestibility of lignocellulosic materials for ethanol production. Experimentally, ground hybrid poplar wood and sugar cane bagasse are placed in plastic bags and a peracetic acid solution is added to the biomass in different concentrations based on oven-dry biomass. The ratio of solution to biomass is 6:1; after initial mixing of the resulting paste, a seven-day storage period at about 20 °C is used in this study. As a complementary method, a series of pre-pretreatments using stoichiometric amounts of sodium hydroxide and ammonium hydroxide based on 4-methyl-glucuronic acid and acetyl content in the biomass is been performed before addition of peracetic acid. The alkaline solutions are added to the biomass in a ratio of 14:1 solution to biomass: the slurry is mixed for 24 hours at ambient temperature. The above procedures give high xylan content substrates. Consequently, xylanase/beta- glucosidase combinations are more effective than cellulase preparations in hydrolyzing these materials. The pretreatment effectiveness is evaluated using standard enzymatic hydrolysis and simultaneous saccharification and cofermentation (SSCF) procedures. Hybrid poplar wood pretreated with 15 and 21% peracetic acid based on oven- dry weight of wood gives glucan conversion yields of 76.5 and 98.3%, respectively. Sugar cane bagasse pretreated with the same loadings gives corresponding yields of 85.9 and 93.1%. Raw wood and raw bagasse give corresponding yields of 6.8 and 28.8%, respectively. The combined 6% NaOH/15% peracetic acid pretreatments increase the glucan conversion yields from 76.5 to 100.0% for hybrid poplar wood and from 85.9 to 97.6% for sugar cane bagasse. Respective ethanol yields of 92.8 and 91.9% are obtained from 6% NaOH/15% peracetic acid pretreated materials using recombinant Zymomonas mobilis CP4/pZB5. Peracetic acid pretreatment improves enzymatic digestibility of hybrid poplar wood and sugar cane bagasse. Based on reduction of acetyl groups in the two lignocellulosic materials, alkaline pre-pretreatments are helpful in reducing peracetic acid requirements in the pretreatment and consequently diminishing growth inhibition of the bacteria that was observed using higher peracetic acid loadings.
Open Access
Nitrogen availability effects on exotic, invasive plant species
(Colorado State University. Libraries, 2000) Lowe, Petra N., author; Lauenroth, William K., advisor; Burke, Ingrid C., committee member; Milchunas, Daniel G., committee member
The invasion of ecosystems by exotic plant species is a serious concern for land managers and conservationists. One of the most universally recognized exacerbating factors of exotic species invasions is disturbance. Human alterations to the global nitrogen cycle have increased atmospheric nitrogen deposition to terrestrial ecosystems worldwide, a disturbance that may encourage the growth of exotic invasive species that are uniquely capable of growing quickly when excess nitrogen is available. I undertook three experiments, one field and two greenhouse, to test the hypothesis that exotic invasive species are specifically adapted to take advantage of high nitrogen conditions, and outcompete natives as nitrogen availability increases, and that native species are better adapted to low nitrogen conditions and outcompete exotics when this nutrient is low. The field experiment examined the response of a disturbed short grass steppe community dominated by exotics to the addition of humus precursors and a labile carbon source intended to reduce plant available nitrogen. I was hypothesized that decreasing nitrogen availability would disadvantage the dominant exotic species and provide and advantage for the native species, returning the community to a vegetative structure more characteristic of undisturbed sites. Results of the experiment showed that decreasing nitrogen availability had no effect on native or exotic species density, richness, or basal cover. A greenhouse study investigated the response of above and belowground biomass, plant height, and nitrogen tissue concentrations of two species, the native Bouteloua gracilis, and the exotic Bromus tectorum, to a gradient in nitrogen availability and competition. The two species were grown under five levels of nitrogen availability and five levels of competition. I hypothesized that the native species would compete better at the low nitrogen levels, but competitive advantage would shift to the exotic as nitrogen availability increased, as some research has shown native species grow better than exotics at low nitrogen levels whereas exotics are only able to support their rapid growth rates when high amounts of resources are available. The exotic species was the better competitor at all nitrogen levels. A second greenhouse study investigated the above and belowground, height, and nitrogen tissue response of two native species, Bouteloua gracilis and Agropyron smithii, and four exotic species, Bromus tectorum, Euphorbia esula, Cirsium arvense, and Centaurea repens, to a gradient in nitrogen availability. I grew the six species individually under five levels of nitrogen availability. I hypothesized that the native plant species would gain more mass than the exotics at the low nitrogen levels, but the exotics would gain more mass at the high nitrogen levels. The native species failed to perform better than the exotics at the lowest nitrogen levels, but only two exotics performed better than the natives at the highest nitrogen levels. My results support the hypothesis that exotic species respond more readily to increasing nitrogen availability than native species, but do not support the hypothesis that all exotic species have a competitive advantage under high nitrogen conditions. Furthermore, my results do not support the hypothesis that native species have a competitive advantage over all exotic invasive weeds at low nitrogen conditions, as one of the exotics, Bromus tectorum, competed and grew comparatively better than the native species even at low nitrogen levels. The success of all exotic invasive weeds cannot be completely attributed to a rapid growth response to nutrient availability; it is likely that different species utilize a combination of strategies to outcompete native plant species.
Open Access
Artificial intelligence based decision support for trumpeter swan management
(Colorado State University. Libraries, 2002) Sojda, Richard S., author; Dean, Denis J., advisor; Fredrickson, Leigh H., committee member; Howe, Adele E., committee member; Loomis, John B., committee member
The number of trumpeter swans (Cygnus buccinator) breeding in the Tri-State area where Montana, Idaho, and Wyoming come together has declined to just a few hundred pairs. However, these birds are part of the Rocky Mountain Population which additionally has over 3,500 birds breeding in Alberta, British Columbia, Northwest Territories, and Yukon Territory. To a large degree, these birds seem to have abandoned traditional migratory pathways in the flyway. Waterfowl managers have been interested in decision support tools that would help them explore simulated management scenarios in their quest towards reaching population recovery and the reestablishment of traditional migratory pathways. I have developed a decision support system to assist biologists with such management, especially related to wetland ecology. Decision support systems use a combination of models, analytical techniques, and information retrieval to help develop and evaluate appropriate alternatives. Swan management is a domain that is ecologically complex, and this complexity is compounded by spatial and temporal issues. The Distributed Environment Centered Agent Framework (DECAF) was successful at integrating communications among agents, integrating ecological knowledge, and simulating swan distributions through implementation of a queuing system. The work I have conducted indicates a need for determining what other factors might allow a deeper understanding of the effects of management actions on the flyway distribution of waterfowl. Knowing those would allow the more refined development of algorithms for effective decision support systems via collaboration by intelligent agents. Additional, specific conclusions and ideas for future research related both to waterfowl ecology and to the use of multiagent systems have been triggered by the validation work.
Open Access
Water quality changes at a streamflow augmentation project, Lower South Platte River, Colorado
(Colorado State University. Libraries, 2003) Watt, Jamey T., author; Durnford, Deanna S., advisor; Sanford, William E., advisor; Stednick, John D., committee member
Flow augmentation projects utilizing managed groundwater recharge serve as a management tool for the conjunctive use of groundwater and surface water. The projects emphasize providing adequate water quantity at the right place and at the right time. However, water quality must be addressed. Mixing of different qualities within such a system can affect water quality both in the river and in the alluvial aquifer. The Tamarack Ranch Groundwater Recharge Project (Project) operates adjacent to the South Platte River in northeastern Colorado. The Project re-times excess flows in the South Platte River using managed groundwater recharge. Surface water, groundwater, and extraction water samples from the site were analyzed for water quality parameters and ionic composition. Water chemistry from the different sample locations determined the spatial and temporal influence of managed recharge activities. Two primary and distinct source waters are present in the system – groundwater and river water. The groundwater is dominated by calcium and bicarbonate. The river water is dominated by sodium / calcium and sulfate. The extraction water is a mixture of these two sources. The application of a simple batch mixing technique determined that the extraction water was about 80% groundwater. This research found that a streamflow augmentation project using managed groundwater recharge does affect water quality. As the system continues to operate, alluvial aquifer water quality will be affected by the surface water quality. A space for time substitution shows how groundwater quality is changing due to the effects of additional river water entering the alluvial aquifer system.
Open Access
A modeling approach to estimating snow cover depletion and soil moisture recharge in a semi-arid climate at two NASA CLPX
(Colorado State University. Libraries, 2004) Holcombe, Julie D., author; Fassnacht, Steven R., advisor
Snow cover depletion and soil moisture recharge are small segments, but crucial hydrological components for cryospheric regions of the earth. The abilities of a one-dimensional mass and energy balance model (SNTHERM) to predict snow cover depletion and Fast All season Soil STrength (FASST) to model the evolution of soil moisture recharge based on observed data from two NASA Cold Land Processes Experiment (CLPX) sites were evaluated. The objective was to investigate both model accuracies in predicting the observed parameters at Buffalo Pass near Steamboat and Illinois River located in North Park, both of which are located in the Colorado Rocky Mountains and are known for their differences in terrain and weather conditions. The results from SNTHERM and FASST and the model performance statistics illustrate that the models overall fit to the observations were excellent at both locations. SNTHERM predicted the snow cover depletion date two days later than the observations at Buffalo Pass and only one day prior to the observations at Illinois River. The timing of snow accumulation and melt at Illinois River was in agreement with the observations at Illinois River, but the magnitude of snow depth was incorrect. The shallow and patchy nature of snow cover and the inconsistent meteorological parameters were problematic for SNTHERM. FASST correctly predicted the magnitude of seasonal soil moisture storage at both sites, but soil moisture recharge prediction was challenging for the model. A lateral flow module and thorough soil data are thought to improve FASST's capability to predict the timing of soil moisture change. SNTHERM and FASST prove to possess the ability to predict snow cover depletion and seasonal soil moisture storage at two radically different field sites.
Open Access
Evaluation of ultrasonic snow depth sensors for automated surface observing systems (ASOS)
(Colorado State University. Libraries, 2005) Brazenec, Wendy Ann, author; Fassnacht, Steven R., advisor; Doesken, Nolan, committee member; Kelly, Gene, committee member; Stednick, John, committee member
In the 1990's the National Weather Service deployed automated surface observing systems at hundreds of airport locations across the country. Prior to the automation, human observers made snow observations every six hours. Once the automated systems were deployed, snow measurements ceased due to the lack of an automated sensor to measure snow. This study explored how well ultrasonic snow depth sensors compared to manual snow observations at nine sites across the country. This study had four objectives: 1.) Develop a method of quality assurance and quality control 2.) Identify factors which affect sensor performance 3.) Compare automated sensors to manual observations of snow depth 4.) Derive an algorithm to estimate six hour snowfall from automated sensor snow depth. A reliable data smoothing/processing technique was achieved using filtering of large variability and smoothing with a moving average to smooth small variations in snow depth. Factors found to affect sensor performance included: snow crystal type, wind speed, blowing/drifting snow, uneven snow surface, extremely low temperatures, and intense snowfall. The Judd and Campbell sensors both did a satisfactory job measuring snow beneath the sensor within ±0.4 inches. Two separate algorithms were created due to differing degrees of precision between the two sensors. It was found that the Campbell sensor did a better job at estimating six hour snowfall than the Judd using an algorithm that calculated snowfall over 5 minute periods and applying a temperature based compaction model to the estimated snowfall. The Campbell agreed with the manual data with an average mean absolute error between measurements of 0.23 inches. The Judd sensor results improved by using an algorithm which calculated snowfall using the change in snow depth over sixty minutes, however, the Campbell results were better using the five minute snowfall algorithm. Overall, both sensors accurately depicted the snow depth on the ground, however the Campbell sensor was more accurate at predicting six hour snowfall using the algorithms presented in this research.
Open Access
Assessment of digital land cover maps for hydrological modeling of the Yampa River Basin, Colorado, USA
(Colorado State University. Libraries, 2005) Repass, Julie Mae, author; Fassnacht, Steven R., advisor
In order to produce satisfactory results from hydrologic models, it is imperative to use good input data. Today there is a multitude of different land cover maps available, and determining which input data map for the model can be unclear. The goal of this study was to quantify the differences between several readily available land cover maps to determine their relative suitability for hydrological modeling of the Yampa River Basin, Colorado. The land cover maps compared in this study are derived from Advanced Very High Resolution Radiometer (AVHRR), Landsat Thematic Mapper (TM), and Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. These maps were compared to a 30-m land cover map modeled from ground data, Landsat imagery, and MODIS imagery, all collected in 2004. This map was regarded as "truth" in this study due to its fine resolution and use of recent ground data and imagery, and was used to rank the public domain land cover data sets. In order to compare the different land cover data sets, all data were first degraded to a common spatial resolution (~30-m) and a common species resolution. Once this was accomplished, the maps were assessed on four levels. The four assessments were based on: (i) the relative agreement of the total aggregated land class percentages after the data had been cross-walked with respect to the reference map; (ii) pixel accuracy; (iii) scene accuracy; and (iv) cumulative streamflow model output from the United States Geological Survey (USGS) Precipitation-Runoff Modeling System (PRMS) in relation to observed cumulative streamflow. The results showed that the pixel and scene accuracies did not correlate with model performance within the Yampa River Basin using the PRMS model. The qualitative comparison of the total aggregated land class percentages helped explain the general trends in the simulation results. It was found that maps with the correct proportion of forested and non-forested areas generally had simulated cumulative streamflow that matched closest to observed cumulative streamflow. Overall, the MODIS-derived land cover maps performed the best in terms of hydrological modeling using PRMS in the Yampa River Basin. However, the model was not found to be particularly sensitive to accurate land cover conditions. As a result, the scene and pixel accuracy results would not necessarily correlate with the model results.
Open Access
Environmental factors associated with cheatgrass invasion in the Gunnison Basin, Colorado
(Colorado State University. Libraries, 2005) Sokolow, Shannon, author; Leininger, Wayne C., advisor; Brummer, Joe E., advisor; Barbarick, K. A., committee member; Milchunas, Daniel G., committee member
Cheatgrass (Bromus tectorum L.) has invaded vast areas of sagebrush (Artemisia tridentata Nutt.) dominated rangeland throughout the western U.S. In the high-elevation, semi-desert, sagebrush ecosystem of the Gunnison Basin, cheatgrass infestations are primarily restricted to disturbed sites. I conducted observational and experimental studies to evaluate: 1) the range of a viable seedbank from the edge of cheatgrass patches into the native communities, 2) the differences in soil characteristics under the cheatgrass invaded and uninvaded communities, and 3) the effects of surface soil disturbance, addition of shredded sagebrush litter, and addition of water to simulate above-normal fall precipitation on cheatgrass establishment and productivity. Results of the observational studies suggest that there are viable cheatgrass seeds up to 2 m into the uninvaded areas of the Gunnison Basin, but for some unknown reason, they do not germinate and/or successfully establish. I observed significantly higher nitrate-nitrogen in invaded areas once the cheatgrass senesced, strong trends towards lower soil organic matter, total organic carbon, total carbon and total nitrogen in the invaded areas, and significantly higher phosphorus-to-iron ratios in cheatgrass invaded areas compared to uninvaded areas. Results of the observational studies suggest that there are likely a variety of interacting environmental conditions that could be preventing the germination or establishment of cheatgrass seeds outside of the cheatgrass patches. Results of my experimental study suggest that land management tools that disturb surface soil or add litter may increase the invasibility of cheatgrass into high-elevation, sagebrush habitats in the Gunnison Basin. There was no significant effect of adding additional water on cheatgrass density, biomass, or seed density, which might have been attributed to the above-normal precipitation (about 2.5 times > 30 year average) that naturally occurred in September 2003 (the water treatment application period). Plots under the sagebrush plants had significantly higher cheatgrass density, biomass, and seed density than interspace plots. In both plot locations, disturbance significantly increased cheatgrass density, biomass, and seed density. Similarly, adding sagebrush litter in interspaces significantly increased cheatgrass density, biomass, and seed density compared to the controls. Despite the significant soil treatment effects and the natural, above-normal precipitation that occurred, the small amount of cheatgrass biomass and seed produced during this study indicates that cheatgrass in the Gunnison Basin is kept in check by a variety of environmental factors.
Open Access
Geostatistical methods for estimating snowmelt contribution to the seasonal water balance in an alpine watershed
(Colorado State University. Libraries, 2006) Hultstrand, Douglas M., author; Fassnacht, Steven R., advisor; Stednick, John, advisor; Doesken, Nolan, committee member; Musselman, Robert, committee member
The performance of nine spatial interpolation models was evaluated to estimate snowmelt contributions to streamflow in the West Glacier Lake watershed (0.61 km2), in the Snowy Range Mountains of Wyoming. Streamflow from the West Glacier Lake watershed has been previously estimated at 40% to 130% greater than measured precipitation inputs. Additional input into the watershed had been attributed to a permanent snowfield in the upper portion of the watershed covering approximately 2.4% of the watershed area. However, the excess output may be a result of inaccurate estimation of water quantities using current precipitation and stream gauging methods. In April 2005, near peak accumulation snow depth measurements and snow density measurements were collected within West Glacier Lake watershed. The distribution of snow water equivalent (SWE) was calculated as the product of snow depth, snow density, and snow-covered-area (SCA). Snow depths were spatially distributed throughout the watershed through nine spatial interpolation models. Snow densities were spatially distributed through a multiple linear regression. The nine spatial snow depth models explained 18% to 94% of the observed variance in the measured snow depths. Co-kriging with solar radiation produced the best results explaining 94% of the observed variance in snow depth measurements. The annual water balance, expressed as equivalent water depths for water year 2005, was total precipitation (1,481 mm), snowpack sublimation (251 mm), and streamflow (1,000 mm), resulting in an evapotranspiration estimate of 230 mm. Estimated SWE from the field survey data was 67% greater than precipitation gauge estimates and accounted for 85% of the annual streamflow. Summer precipitation was not a significant contributor to the annual hydrograph and was also less than snowpack sublimation. Precipitation gauge values were unrepresentative of actual precipitation depths, and several spatially distributed snow depth models provided better estimates of precipitation inputs.
Open Access
The effects of input data degradation on hydrological model performance for a snowmelt dominated watershed
(Colorado State University. Libraries, 2006) McKim, Scott D., author; Fassnacht, Steven R., advisor
The quality and quantity of hydrometeorological data used as input to a hydrologic model is varied and the output compared to observed historical flows. Temperature and precipitation data were used to feed the National Weather Service River Forecast System (NWSRFS); this hydrologic model outputs streamflow and is used daily throughout the country to forecast streamflows. NWSRFS is a lumped empirical model developed in the 1970s for the NWS and is calibrated in this study to model a portion of the snowmelt dominated Yampa River watershed in northwest Colorado. An analysis scheme is followed to capture the model's dependence on representative meteorological stations located in an around the modeled basin. Many regions in the United States experience meteorological and hydrological data scarcity issues. Operationally this becomes important when the available data is insufficient enough to produce reliable model outputs. Similar to Tsintikidis et al. (2002) concluding that the installation of additional rain gauges in a modeled basin would decrease the error of precipitation measurements in the model, we sought to find if increasing data input into a model, both the quantity and quality given by site representivity, will increase the accuracy of our model runs. The study basin was chosen for its snowmelt dominance characteristic. Mean areal precipitation and temperature values for the modeled zones are developed individually in each analysis scheme by the arrangement of stations used in each sensitivity analysis. A statistical analysis of the relative difference between model runs and archived observed values is performed in an effort to illustrate the effect of different model input data arrangements on model simulations. This study aimed at testing the tenable assertion that subtracting hydrometeorological data from a model's dataset would decrease the accuracy of forecasted stream flows from that model. Stream flows and snow water equivalence are analyzed to test the model's sensitivity to the amount of data used. Since the NWSRFS uses predetermined weights to determine MAPs, the number of stations used does not significantly affect model output. The usage of predetermined weights maintains a consistent year-to-year MAP. Varying the MAT station configuration showed a more sizeable effect than the MAP scheme illustrated. Though this procedure could and should be replicated for other hydroclimates and for basins with different sizes, the specific results are not transferable to other basins. The basin modeled is very heavily snowmelt dominated; this quality, as well as it size, climate, topography, and available hydrometeorological stations all influence model results; altering any of these would change the model performance.
Open Access
Instream flow methodologies: an evaluation of the Tennant method for higher gradient streams in the national forest system lands in the western U.S.
(Colorado State University. Libraries, 2006) Mann, Jennifer, L., author; Fassnacht, Steven R., advisor; Merritt, David, committee member; Rathburn, Sara, committee member
In 1976 Donald Tennant introduced a method for determining instream flow requirements for fish, known as the 'Montana method', or more commonly the Tennant method. The method uses a percentage of average annual flow (AAF) to determine fish habitat quality. From 58 cross sections from 11 streams in Montana, Nebraska, and Wyoming, Tennant concluded that 10% of AAF is the minimum for short term fish survival, 30% of AAF is considered to be able to sustain fair survival conditions, and 60% of AAF is excellent to outstanding habitat. These quantities are employed internationally, regardless of physical and hydrologic setting, due to the simplicity of using only the average annual hydrograph. The purpose of the current study was to determine under what conditions Tennant's fixed percent AAF values apply, to specifically evaluate Tennant's original width, depth, and velocity measurements, to evaluate the applicability of Tennant's percent of AAF, as compared to other methods of determining minimum instream flows, and to determine if there are regional characteristics that relate to the applicability of the Tennant method. Tennant's method was tested to see if percent AAF actually can be used as a surrogate for other hydraulic measures, such as width, depth, and velocity. These physical parameters have been used in other studies to quantify instream flow used for fish. The two other methods that were used in the comparisons were the wetted perimeter method and the physical habitat simulation system (PHABSIM). A set of regional characteristics were used to look for region specific patterns. These characteristics including: stream type, state, ecoregion, and hydro-climatic regime. A total of 151 cross sections were analyzed on seventy river segments throughout the western U.S. (California, Colorado, Idaho, Montana, Oregon, Utah, and Washington). The streams were classified as pool-riffle, plane bed, step-pool, and dune-ripple. This study will offer resource managers additional information on the applicability of the Tennant method for determining instream flow needs for the physical, biological, and social setting. This study concluded that Tennant's original dataset was not representative of streams in the western United States. Data collected from lower gradient streams in Nebraska followed the patterns set forth by Tennant much more closely, and therefore the Tennant method is more applicable in similar low gradient streams (slope less than 1%). In higher gradient streams the use of the Tennant method should be with caution and be restricted to planning stages of instream flow recommendations. Further validation and method adaptation is recommended when using the Tennant method for higher gradient stream types. The Tennant method should be used in instream flow protection scenarios and not in restoration scenarios because of the method's assumption that the current average annual hydrograph represents the optimal fish habitat.
Open Access
Maintaining fuel treatments with prescribed fire in ponderosa pine forests of the Black Hills, South Dakota
(Colorado State University. Libraries, 2007) Battaglia, Michael A., author; Smith, Frederick W., advisor; Shepperd, Wayne D., advisor
Recent wildfires in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests have increased efforts to create forest structures that reduce the risk of crown fire. In the Black Hills, these fuel-reduction treatments often result in a new cohort of ponderosa pine regeneration. If no action is taken, the efficacy of these fuel treatments eventually diminishes as the regeneration grows and creates a ladder fuel complex. In this dissertation, I examine the utility of using prescribed fire to control this regeneration. I also explore if restoration of historical forest structure would result in reduced crown fire risk.