Department of Forest and Rangeland Stewardship

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https://hdl.handle.net/10217/100430

These digital collections include theses, dissertations, faculty publications, and student publications from the Department of Forest and Rangeland Stewardship. Due to departmental name changes, materials from the following historical departments are also included here: Forest and Wood Sciences; Forest Management and Wood Utilization; Forest, Rangeland, and Watershed Stewardship; Forest Recreation; Forest Recreation and Wildlife Conservation; Forest Sciences; Forestry; Range Management; Range Science; Rangeland Ecosystem Science; Watershed Sciences.

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Open Access
Watershed analysis of the Little South Fork of the Cache la Poudre River, Larimer County, Colorado
(Colorado State University. Libraries, 1962) Colorado State University. Watershed Management Unit, author; Johnson, Kendall L., editor
Open Access
Height growth in relation to crown size in juvenile lodgepole pine
(Colorado State University. Libraries, 1967-10) Mogren, Edwin W., author; Colorado State University, College of Forestry and Range Management, publisher
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
Biomass allocation response of sitanion hystrix to soil water stress
(Colorado State University. Libraries, 1986) McDonell, M. Laurie, author
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
Carbon dynamics and estimates of primary production by harvest, 14C dilution, and 14C turnover
(Colorado State University. Libraries, 1992-04) Lauenroth, W. K., author; Milchunas, D. G., author; Ecological Society of America, publisher
Large plots of native shortgrass steppe were labeled with 14C to assess short-term patterns of carbon allocation and the long-term process of herbivory, death, and decomposition, and to compare estimates of net aboveground, crown, and root primary production using 14C dilution, 14C turnover, and traditional harvest methods. Stabilization of labile 14C via translocation, incorporation into structural tissue, and respiration and exudation required one growing season. Exudation was 17% of plant 14C after stabilization. Estimates of turnover time for leaves, crowns, and roots by 14C turnover were 3, 5, and 8 yr, respectively, yielding estimates of belowground production that were much lower than previously thought. Estimates of aboveground production by 14C turnover were close to those obtained by harvest of peak-standing crop, but lower than reported values obtained by harvest maxima-minima. Estimates of root production by harvest maxima-minima were zero in 2 of 4 yr. 14C turnover appeared to provide reliable estimates of aboveground, crown, and root production. In contrast to reliable estimates by 14C turnover, 14C dilution estimates of root production were anomalous. The anomalous estimates were attributed to a nonuniform labeling of tissue age classes resulting in differential decomposition/herbivory of 14C:12C through time, as well as movement and loss of labile 14C through the first growing season. Isotope-dilution methodologies may be unreliable for any estimate of pool turnover when the labeling period is not as long as pool-turnover time. Problems and biases associated with traditional harvest maxima-minima methods of estimating aboveground primary production are well known, but are greatly exacerbated when the method is used to estimate root production. Estimates of root production by 14C dilution were unrealistic. 14C turnover methodology provided reliable estimates of production in this community.
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
Inertia in plant community structure: state changes after cessation of nutrient-enrichment stress
(Colorado State University. Libraries, 1995-05) Lauenroth W. K., author; Milchunas, D. G., author; Ecological Society of America, publisher
Water, nitrogen, and water-plus-nitrogen at levels beyond the range normally experienced by shortgrass steppe communities were applied from 1971 through 1975, plant populations were sampled through 1977, and the results of the experiment were published. Upon revisiting the plots in 1982, we found it apparent that large changes had occurred since 1977. Sampling was re-established in 1982 to follow trajectories of recovery. Our purposes in this paper are to examine how conclusions from this study changed through time, and discuss implications of these changes for monitoring potentially stressed ecosystems. Although productivities increased, dissimilarities in plant species composition at the end of the 5 year of nutrient treatments were not significantly different from controls. Two years after cessation of the treatments exotic "weed" species were increasing in water plus-nitrogen treated communities, and community dissimilarities were diverging in water and water-plus-nitrogen treated communities. Seven years after cessation of treatments all communities were significantly different from controls. Exotics were more than ten times more abundant in water-plus-nitrogen and nitrogen treated communities than they had been2 year post-treatment. A consistent trend in recovery of all treated communities was evident over the next 5 yr. However, the trend towards recovery reversed over the next four consecutive years in the previously water-plus-nitrogen and water treated communities. The four-to-five year cycles in species composition and abundance of exotics towards, and then away from, conditions in undisturbed control communities were not related to weather, but large accumulations of litter suggested biotic regulation. Inertia of existing plant populations, or the tendency to continue to occupy a site when conditions become unfavorable, can mask both future deterioration in ecosystem condition and unstable behavior resulting from environmental stressors. Time lags in initial response means that an ecosystem can pass a threshold leading to transitions to alternate states before it is evident in structural characteristics such as species composition. Global climate change and sulfur and nitrogen oxide pollutants also have the potential to act as enrichment-stressors with initial time lags and/or positive effects and cumulative, subsequent negative effects, rather than as disturbance forces with immediate negative impacts. Sociopolitical systems, however, often require change in biological variables or negative impacts before acting to ameliorate environmental problems. The manner in which conclusions changed at various periods in time, and the potential for time lags in responses of species populations, raises questions about which variables are most useful for detection of stress and how long studies must last to be useful.
Open Access
Interactions between individual plant species and soil nutrient status in Shortgrass Steppe
(Colorado State University. Libraries, 1995-06) Burke, Ingrid C., author; Vinton, Mary Ann, author; Ecological Society of America, publisher
The effect of plant community structure on nutrient cycling is fundamental to our understanding of ecosystem function. We examined the importance of plant species and plant cover (i.e., plant covered microsites vs. bare soil) on nutrient cycling in shortgrass steppe of northeastern Colorado. We tested the effects of both plant species and cover on soils in an area of undisturbed shortgrass steppe and an area that had undergone nitrogen and water additions from 1971 to 1974, resulting in significant shifts in plant species composition. Soils under plants had consistently higher C and N mineralization rates and, in some cases, higher total and microbial C and N levels than soils without plant cover. Four native grasses, one sedge, and one shrub differed from one another in the quantity and quality of above- and belowground biomass but differences among the six species in soil nutrient cycling under their canopies were slight. However, soils under bunchgrasses tended to have higher C mineralization and microbial biomass C than soil under the rhizomatous grass, Agropyron smithii. Also, the one introduced annual in the study, Kochia scoparia, had soils with less plant-induced heterogeneity and higher rates of C and N mineralization as well as higher levels of microbial biomass C than soils associated with the other species. This species was abundant only on plots that had received water and nitrogen for a 4-yr period that ended 20 year ago, where it has persisted in the absence of resource additions for 20 yr, suggesting a positive feedback between plant persistence and soil nutrient status. Plant cover patterns had larger effects on ecosystem scale estimates of soil properties than the attributes of a particular plant species. This result may be due to the semiarid nature of this grassland in which plant cover is discontinuous and decomposition and nutrient availability are primarily limited by water, not by plant species-mediated characteristics such as litter quality. That local plant-induced patterns in soil properties significantly affected ecosystem scale estimates of these properties indicates that consideration of structural attributes, particularly plant cover patterns, is critical to estimates of ecosystem function in shortgrass steppe.
Open Access
Soil organic matter recovery in semiarid grasslands: implications for the Conservation Reserve Program
(Colorado State University. Libraries, 1995-08) Coffin, Debra P., author; Lauenroth, William K., author; Burke, Ingrid C., author; Ecological Society of America, publisher
Although the effects of cultivation on soil organic matter and nutrient supply capacity are well understood, relatively little work has been done on the long-term recovery of soils from cultivation. We sampled soils from 12 locations within the Pawnee National Grasslands of northeastern Colorado, each having native fields and fields that were historically cultivated but abandoned 50 years ago. We also sampled fields that had been cultivated for at least 50 years at 5 of these locations. Our results demonstrated that soil organic matter, silt content, microbial biomass, potentially mineralizable N, and potentially respirable C were significantly lower on cultivated fields than on native fields. Both cultivated and abandoned fields also had significantly lower soil organic matter and silt contents than native fields. Abandoned fields, however, were not significantly different from native fields with respect to microbial biomass, potentially mineralizable N, or respirable C. In addition, we found that the characteristic small-scale heterogeneity of the shortgrass steppe associated with individuals of the dominant plant, Bouteloua gracilis, had recovered on abandoned fields. Soil beneath plant canopies had an average of 200 g/m2 more C than between-plant locations. We suggest that 50 years is an adequate time for recovery of active soil organic matter and nutrient availability, but recovery of total soil organic matter pools is a much slower process. Plant population dynamics may play an important role in the recovery of shortgrass steppe ecosystems from disturbance, such that establishment of perennial grasses determines the rate of organic matter recovery.
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.