Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 43-47). Also available on the World Wide Web.

Knowledge of old-growth Juniperus occidentalis woodlands, which occur in central and eastern Oregon, is limited. Wise management of these woodlands necessitates a better understanding of the community ecology. The community structure of woodlands at seven sites in three areas of central Oregon was studied. Measurements taken at nine plots per site included tree density, canopy cover, heights, diameters, and canopy areas; cover of each understory species and other ground covers; density of shrubs by species and condition; density of woody debris as downed pieces and standing dead trees; and topographic and soil parameters. Tree cores were taken for aging, although heartwood rot is pervasive in older trees. Factors of interest included cover and richness in all vegetative layers, variability within and between sites, and comparison of J. occidentalis woodlands to other old-growth communities. J. occidentalis woodlands were found to have a minimum of 80 trees over 200 years old per hectare, canopy cover of 10-35%, and understory cover of less than 20%. Woody detritus was primarily retained aloft and decomposed by weathering. Tree morphology was highly variable, but decadence was common. Outward physical attributes did not appear to be reliable predictors of tree age. Shrub cover was strongly correlated (r��=0.66) with the combination of elevation, ground cover by rock, and clay content of the soil. Perennial grass cover increased with elevation and the sand-sized soil fraction (r��=0.46). Understory cover, dominated by perennial grass, showed a weaker correlation with the same parameters (r��=0.20). Other significant findings included correlation of juniper cover with elevation, sand. and heat load (r��=0.38). Tree cover was found to increase by almost 1% for each 1% increase in sand content of the soil and by almost 8% for each 100m increase in elevation, while heat load, based on aspect. had a smaller effect. Plots grouped strongly by area. suggesting that there is a stronger influence of area than site on community composition for most of the sites and that differences between areas overwhelm the differences within areas. / Graduation date: 1999

This component of the Conservation Innovation Grants Summer Burning project evaluates the economic feasibility of using prescribed fire that exceeds the current Natural Resource Conservation Service (NRCS) technical standards as a rangeland restoration practice on privately owned land in Texas. This study has four objectives: (1) Evaluate the economic effectiveness of using prescribed extreme burns as a rangeland restoration tool compared to other rangeland restoration strategies. (2) Provide economic research results that will facilitate a review of the technical standards, specification, and potential policy changes by the NRCS with respect to the use of prescribed extreme burning. (3) Assess economic effects of extreme fire when used in combination with other treatment practices over a 20 year planning horizon. (4) Through modeling, forecasting, and simulation assess the risk associated with the use of extreme prescribed fire, with respect to weather (rainfall) conditions. The research covers four contiguous counties in each of three eco-regions in Texas: Rolling Plains, Edwards Plateau, and the South Texas Plains. Focus group meetings with landowners and NRCS/Extension personnel were held in each region to obtain preliminary information including common rangeland uses, most problematic invasive brush species, and the most commonly used treatment methods and associated costs. The primary invasive species in each region include: Rolling Plains – Prickly Pear (Opuntia phaecantha); Edwards Plateau – Redberry and Ashe Juniper (Juniperus ashei Buchh. And J. pinchotii Sudw., respectively); South Texas Plains – Huisache (Acacia smallii Isely). Mesquite (Prosopis glandulsa Torr.) was identified as a common invasive brush species across all three regions. When extreme fire was compared to the most commonly used invasive brush treatments, assuming the treatment was instituted in year one, it was economically superior in all cases and feasible (Net Present Value > 0 and Benefit/Cost Ratio >1) in all but two cases. The inclusion of forecasted rainfall figures with the combination of using the most commonly used brush treatment with extreme fire proved to substantially reduce the risk of instituting the treatment regimes. The probability distribution of NPVs was significantly smaller when treatment practices were spread over ten years and parcels than when treatment was restricted to the first year and whole ranch.

Thermal gasification of biomass is being considered as one of the most promising technologies for converting biomass into gaseous fuel. Here we present results of gasification, using an adiabatic bed gasifier with air, steam as gasification medium, of mesquite and juniper. From Thermo-gravimetric analyses the pre-exponential factor (B) and activation energy of fuels for pyrolysis were obtained using single reaction models (SRM) and parallel reaction model (PRM). The single reaction model including convention Arrhenius (SRM-CA) and maximum volatile release rate model (SRM-MVR). The parallel reaction model fits the experimental data very well, followed by MVR. The CA model the least accurate model. The activation energies obtained from PRM are around 161,000 kJ/kmol and 158,000 kJ/kmol for juniper and mesquite fuels, respectively. And, the activation energies obtained from MVR are around100,000 kJ/kmol and 85,000 kJ/kmol for juniper and mesquite fuels, respectively. The effects of equivalence ratio (ER), particle size, and moisture content on the temperature profile, gas composition, tar yield, and higher heating value (HHV) were investigated. For air gasification, when moisture increased from 6% to 12% and ER decreased from 4.2 to 2.7, the mole composition of the dry product gas for mesquite varied as follow: 18-30% CO, 2-5% H2, 1-1.5% CH4, 0.4-0.6% C2H6, 52-64% N2, and 10-12% CO2. The tar yield shows peak value (150 g/Nm^3) with change in moisture content between 6-24%. The tar collected from the gasification process included light tar and heavy tar. The main composition of the light tar was moisture. The chemical properties of heavy tar were determined. For air-steam gasification, H2 rich mixture gas was produced. The HHV of the mesquite gas increased first when S: F ratio increased from 0.15 to 0.3 and when the S: F ratio increased to 0.45, HHV of the gas decreased. Mesquite was blended with the Wyoming Powder River Basin (PRB) coal with ratio of 90:10 and 80:20 in order to increase the Tpeak and HHV. It was found that the Tpeak increased with the increase of PRB coal weight percentage (0% to 20%).

This component of the Conservation Innovation Grants Summer Burning project evaluates the economic feasibility of using prescribed fire that exceeds the current Natural Resource Conservation Service (NRCS) technical standards as a rangeland restoration practice on privately owned land in Texas. This study has four objectives: (1) Evaluate the economic effectiveness of using prescribed extreme burns as a rangeland restoration tool compared to other rangeland restoration strategies. (2) Provide economic research results that will facilitate a review of the technical standards, specification, and potential policy changes by the NRCS with respect to the use of prescribed extreme burning. (3) Assess economic effects of extreme fire when used in combination with other treatment practices over a 20 year planning horizon. (4) Through modeling, forecasting, and simulation assess the risk associated with the use of extreme prescribed fire, with respect to weather (rainfall) conditions. The research covers four contiguous counties in each of three eco-regions in Texas: Rolling Plains, Edwards Plateau, and the South Texas Plains. Focus group meetings with landowners and NRCS/Extension personnel were held in each region to obtain preliminary information including common rangeland uses, most problematic invasive brush species, and the most commonly used treatment methods and associated costs. The primary invasive species in each region include: Rolling Plains – Prickly Pear (Opuntia phaecantha); Edwards Plateau – Redberry and Ashe Juniper (Juniperus ashei Buchh. And J. pinchotii Sudw., respectively); South Texas Plains – Huisache (Acacia smallii Isely). Mesquite (Prosopis glandulsa Torr.) was identified as a common invasive brush species across all three regions. When extreme fire was compared to the most commonly used invasive brush treatments, assuming the treatment was instituted in year one, it was economically superior in all cases and feasible (Net Present Value > 0 and Benefit/Cost Ratio >1) in all but two cases. The inclusion of forecasted rainfall figures with the combination of using the most commonly used brush treatment with extreme fire proved to substantially reduce the risk of instituting the treatment regimes. The probability distribution of NPVs was significantly smaller when treatment practices were spread over ten years and parcels than when treatment was restricted to the first year and whole ranch.

Biogeographic patterns of animals are shaped by biotic interactions, such as competition, and by abiotic factors, such as climate. Mountain Chickadees (Parus gambeli) and Juniper Titmice (Parus ridgway) are permanent residents of regions of western North America and are ecologically similar, but have different northern range limits. l measured several physiological variables, including basal metabolic rate (BMR), peak metabolic rate (PMR = maximal thermogenic capacity), metabolic response to varying environmental temperature (MRT), evaporative water loss (EWL), and daily energy expenditure (DEE) for summer-and winter-acclimatized Mountain Chickadees and Juniper Titmice to determine if seasonal and interspecific variation in cold tolerance and thermogenic ability shape the northern range distribution of these two species. In addition, I examined the ecological consequences of nocturnal hypothermia and cavity roosting in seasonally acclimatized Mountain Chickadees and Juniper Titmice. Winter birds tolerated colder test temperatures than summer birds for both species This improved cold tolerance was associated with a significant increase in PMR in winter chickadees (27.1 %) and titmice (114%) compared to summer. BMR was significantly higher in winter birds (16.0%) compared to summer birds for both species. BMR and PMR were significantly higher for chickadees compared to titmice in both summer and winter. Winter chickadees were able to withstand colder test temperatures than winter titmice. The Mountain Chickadee's lower critical temperature is lower than the Juniper Titmouse's in summer and in winter. The Mountain Chickadee's upper critical temperature is also lower than the Juniper Titmouse's and chickadees also had significantly higher evaporative water loss rates compared to titmice. Seasonal acclimatization in Mountain Chickadees involves insulatory as well as metabolic changes. For Juniper Titmice winter acclimatization appears to be primarily a metabolic process. The laboratory metabolism data for activity costs associated with DEE revealed that foraging energy requirements were not significantly higher than alert perching energy requirements. DEE was significantly higher (P<0.05) in winter-acclimatized chickadees and titmice compared to their summer counterparts. The marked increase in calculated DEE in winter birds compared to summer contrasts a pattern of increased DEE in the breeding season for several avian species. The data from this study indicate that the northern range limit of small birds can be limited by energetic and water balance demands.

Two experimental rainfall simulation plots in the Edwards Aquifer region of Texas were established to measure the effects of brush clearing on surface and subsurface water movement pathways. Multi-stage rainfall simulations were carried out at a site with Juniperus ashei (ashe juniper) cover both before and after brush removal, with three replications of a particular rainfall event for each vegetation condition. Similar simulations were carried out on a plot with a longstanding grass cover. Both plots included trenches at their downhill ends for observation of shallow lateral subsurface flow. Canopy interception was found to represent a major water loss, with interception of 32.7 mm for an average 166 mm, 5.25 hr rainfall event. Brush clearing had little impact on surface runoff, with no overland flow occurring at the juniper plot for either vegetation condition, while 31.9 percent of applied rainfall moved as overland flow at the grass plot. This difference was attributed to differences in the structure and permeability of the epikarst. Brush removal caused significant (90 percent confidence level) reduction in shallow lateral subsurface flow into the trench after brush removal, with 56.7 percent of water reaching the surface entering the trench for the pre-cut condition and only 43.4 percent for the post-cut condition. However, subsurface water movement through other pathways increased from 31.0 to 54.1 percent after brush removal. This additional water, due to removal of canopy interception, could either move off-site through conduit and fracture flow or remain on site as storage in conduits, unconsolidated caliche/marl layers, or in soil pockets. Two tracer tests with fluorescent dyes were also conducted using simulated rainfall to assess discrete flow paths discharging into the trench at the downhill end of the juniper plot. Analysis of samples from sixteen outlet locations revealed that not all areas of the plot were connected hydraulically to the trench. Additionally, subsurface flow paths were found to have a high degree of interconnection, linking conduit flow outlets with multiple inlet locations on the plot surface. Conduits showed strong connection with an area surrounding juniper vegetation, with rapid water flow (up to 2.4 m/h) from this area.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 108-113). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Norma Fowler. Vita. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 46-55). Also available on the World Wide Web.