An important management practice within the 60-80 million acres of Pinyon-Juniper woodlands is to convert these woodlands to open rangelands. The success or failure of seedling adapted grasses in place of trees is contingent upon the revegetation techniques employed and upon fortuitous weather patterns. In order to formulate policy for Pinyon-Juniper control decisions, persons responsible for such policies need to know the risks of introducing range grasses into given areas. This thesis is essentially a hypothesis concerning the magnitude of such risks. Pinyon-Juniper control has been practiced widely in the five state areas of Arizona, Colorado, Nevada, New Mexico, and Utah. Justification for control and conversion of the woodlands to open grazing areas rests on the assumption that the trees have little apparent utility and, therefore they should be replaced by a grass resource which has relatively greater value. In its extreme form the assumption involves the notion that the trees are actually detrimental to the productivity of the land. they become a hindrance to the growth of various forms of plant life considered desirable. Considerable investment, primarily at the expense of society, has been incurred in the transformation process. Until recent years control projects have been limited to the most accessible sites and areas "invaded" by Pinyon-Juniper trees. At present the conversion place has slackened due to the limited number of remaining accessible sites in some areas, but more importantly to the fact that the projects have had a history of mixed success. While certain rules of thumb have been put forth to explain the nature of the factors influencing seedling emergence and increased forage production, these are so volatile that an apprehension of failure exists among land managers. The intensity of investment can only be balanced against risk levels if there is basic understanding of the roles played by the variables influencing seedling establishment and forage increase. Both policy and nonpolicy (not subject to human manipulation) variables must be identified and their influences upon success measured. The analysis that follows begins by setting forth the objectives to be achieved in evaluating the tree conversion process and its associated risk. Next a theory of range grass seedling establishment is presented. The appropriate variables are identified and an "establishment" model is applied to the empirical data. A third section specifically treats weather as a major influence upon seedling emergence and forage production. A model expressed in probabilistic terms, employing the Markov property is applied to available data to evaluate weather index movements. Finally having dealt with emergence, a theory is developed to explain expected forage production in the period following emergence. The parameters of the associated model are obtained from empirical data.

A profit criterion which will make possible the selection of optimum conversion practices in the Pinyon-Juniper woodlands can be made operational if: (a) it is possible to predict eradication costs and resulting total costs (eradication costs, seed costs, and seed application costs) , and (b) it is possible to determine for age production resulting from initial eradication, as well as when it reaches absolute minimum allowable limit due to tree re-growth . Knowledge of the above relationships makes it possible to determine the optimum practice.

Axelrod (1958) suggested that the late Tertiary shift in regional climate -- the elimination of summer rains -- had a profound influence on the evolution of biotic provinces in the American southwest. In particular, the taxa endemic to biotic provinces characterized by summer drought, e.g., the Mojave Desert, should be derived from ancestors that likely inhabited regions of summer rain, e.g., the Chihuahuan Desert. Further, the derived features of summer-drought taxa should be related to water stress. I examined Axelrod's thesis, using a combination of phylogenetic systematics, physiological ecology, and vicariance biogeography. The first chapter is a cladistic study of the pinyon pines, 13 taxa of small trees that range from the summer-wet regions of Mexico to the summer drought regions of Nevada and California. A parsimony analysis using twenty morphological characters showed that the most recently derived pinyons are from regions of summer drought. The "summer-drought" taxa are characterized by relatively few needles per fascicle. Because fewer needles per fascicle results in a reduction in the needle surface-to-volume ratio, Haller (1965) hypothesized that fewer needles in pines is an adaptation to reduce transpirational water loss. The second chapter reports on a two year study of the xylem pressure potentials of single- and double-needled fascicles of hybrid pinyons in central Arizona. The results showed no significant differences between single- and double-needles. I concluded that either needle morphology does not effect water relations, or that the relatively high precipitation during the study did not allow significant water stress to occur. The third chapter uses the methods of vicariance biogeography to search for a common pattern of relationship between southwestern biotic provinces, as indicated by the relationships of their endemic taxa. Using a biogeographic parsimony analysis, I compared the area cladograms of six taxa -- junipers, pinyon pines, the composite Palafoxia, hedgehog cactus, desert tortoises, and gecko lizards. The most parsimonious area cladogram supports Axelrod's (1958) hypothesis, but also shows that some taxa, notably the junipers, support other patterns of area relationships, e.g., summer-drought primitive. I suggest that there is no single pattern of area relationships because of the effects of the Pleistocene (including dispersal and extinction) and vicariance events other than the Tertiary climatic change, e.g., the separation of the Baja peninsula from mainland Mexico during the Miocene.

A physically-based, user friendly, hydrologic computer simulation model was developed for pinyon-juniper woodland watersheds. The data requirements are minimum, requiring vegetation conditions, basic soil survey information, and daily values for precipitation and temperature. The model predicts runoff from cleared and uncleared watersheds by simulating hydrologic processes on a daily basis. The model was tested with data from small pinyon-juniper watersheds in central Arizona. A crack-forming vertisol was the dominant soil type, and a special feature for addressing its effects on runoff was included. No significant difference between predicted and observed annual runoff was found at the ninety-five percent confidence level.

During 1973 and 1974 a water quality study was conducted in San Juan County, southeastern Utah. In 1973, baseline water quality data was collected from study locations which had been chained to remove pinyon-juniper vegetation six years earlier. The area had been chained under two different techniques: (1) doubled chained, with debris-left-in-place and (2) chained, with debris windrowed. An "undisturbed, natural" woodland was left between these two treatments in order to serve as a control area. In the fall of 1973 and spring of 1974 secondary treatments of burning and grazing were superimposed upon the debris-in-place and windrowed sites, respectively. All water collected and analyzed for the several water quality parameters was generated through use of a small plot Rocky Mountain infiltrometer which creates a simulated rainstorm. Resultant runoff was collected and analyzed for each of the parameters in question. No significant changes were noted from these point source measurements in terms of fecal and total coliform production (fecal pollution bacterial indicators). The point source approach was a technique for sampling a much larger land area through many small plots (0.23 m2). There is an element of risk involved whenever the data generated from such a small area is projected to the larger land area. Based on this small plot data it appears, however, that this level of livestock grazing (2 hectares/AUM) does not constitute a public health hazard in terms of fecal pollution indicators when grazed on similar semi-arid watershed areas. Some significant changes were noted following burning, however. Significant increases in potassium and phosphorus were noted. Apparently the fire "released" these nutrients which were tied up in the debris scattered across the site. Potassium registered an increase of about 4 ppm (400 percent) while phosphorus showed an increase of about 0.2 ppm (400 percent). No significant treatment changes were detected for sodium, calcium, or nitrate-nitrogen, however. Sediment production was also measured under the various treatment conditions. High natural variability is present among these sites, and no significant treatment effect was defected following our prescribed burning or grazing treatments. Infiltration rates were also monitored. No significant treatment differences were noted among the initial treatment means during 1973. Apparently any differences in infiltration rates due to chaining technique had been overcome by the passage of six years since the initial chaining had been completed. During 1974, however, secondary treatment was in effect. Infiltration rates on the grazed and burned watersheds were significantly depressed during certain time intervals in comparison to the "undisturbed, natural" woodland location. Apparently this level of secondary treatment could have an effect on the hydrology of the area, at least in terms of infiltration rates.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "August, 2006." Includes bibliographical references (leaves 103-113). Online version available on the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "August, 2005." Includes bibliographical references (leaves 110-117). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "August 2006." Includes bibliographical references (leaves 28-37). Online version available on the World Wide Web.

Pinyon-juniper woodland encroachment threatens ecosystem function and diversity on sagebrush steppe. Decreased fire frequency likely favors proliferation of pinyon-juniper woodlands and subsequent decline in desirable understory species. Increased tree cover produces hazardous canopy fuel loads that contribute to severe crown fires and threaten life and property at the wildland-urban-interface. Mechanical mastication converts large canopy fuels into small woody debris, altering wildfire dynamics from a potential crown fire to a more controllable surface fire. We measured fuel loading and cover on untreated, masticated, and masticated + burned treatments on 30-m transects within 30 X 33-m subplots, representing 45 different sites throughout Utah. All variables were analyzed using mixed-model analysis of covariance with untreated or pretreatment tree cover as the covariate. Shredding trees reduced large-diameter fuels to primarily 10-hour fuels (6.4-25.4 mm diameter). Reduced fuel sizes, fuel redistribution, and fuelbed compactness resulting from mastication treatments can aid wildfire suppression. Masticated + burned treatments effectively reduced woody surface fuel loading to that of pretreatment conditions. Prescribed burning could be used outside the growing season in cool-weather, high-moisture conditions to remove surface fuels, mitigating lethal soil heating and plant mortality. Shrub loading was not adversely affected by mastication treatments, but was significantly reduced with masticated + burned treatments. Masticated and masticated + burned treatments significantly increased herbaceous fuel loading. Treating at lower tree cover values reduced fuel buildup, and provided more opportunity for a positive herbaceous response. Fuel loading estimates measured in this study were provided to populate fire behavior models for mastication treatments on our study sites when such models become available.

Nuwuvi (Southern Paiute) have inhabited the southern Great Basin for thousands of years, and consider Nuvagantu (where snow sits) in the Spring Mountains landscape to be the locus of their creation as a people. Their ancestral territory spans parts of Nevada, Utah, Arizona, and California. My research identifies and describes the heterogeneous character of Nuwuvi ecological knowledge (NEK) of piñon-juniper woodland ecosystems within two federal protected areas (PAs) in southeastern Nevada, the Spring Mountains National Recreation Area (SMNRA) and the Desert National Wildlife Refuge (DNWR), as remembered and practiced to varying degrees by 22 select Nuwuvi knowledge holders. I focus my investigation on four primary aspects of NEK. First, drawing from data obtained through ethnoecological research, I discuss how Nuwuvi ecological knowledge evolved through protracted observation and learning from past resource depletions, and adapted to various environmental and socio-economic drivers of change induced since Euro-American incursion. Second, I argue that Nuwuvi management practices operate largely within a framework of non-equilibrium ecology, marked by low to intermediate disturbances and guided by Nuwuvi conceptions of environmental health and balance. These practices favor landscape heterogeneity and patchiness, and engender ecosystem renewal, expanded ecotones, and increased biodiversity. I then consider the third and fourth aspects of NEK as two case studies that consider NEK at the individual, species, population, habitat, and landscape scales. These case studies operationalize NEK as a relevant body of knowledge and techniques conducive to collaborative resource stewardship initiatives with federal land management agency partners. In the first case study I suggest that the Great Basin piñon pines are Nuwuvi cultural keystone species (CKS), evaluating their central importance to Nuwuvi according to several criteria including number of uses, role in ritual and story, and uniqueness relative to other species. In the second case study I contend that local social institutions regulated Nuwuvi resource use in the past and in some cases continued to do so at the time of study. These local social institutions included a system of resource extraction and habitat entrance taboos that may have mitigated impacts and supported sustainable resource use and conservation. The implications of this research are that Nuwuvi ecological knowledge, disturbance-based adaptive management practices, and resource and habitat taboos are relevant to contemporary land management concerns in piñon-juniper woodlands, offering complementary approaches to adaptive management as practiced in the SMNRA and the DNWR despite divergent epistemological foundations. My research contributed to the Nuwuvi Knowledge-to-Action Project, an applied government-to-government consultation, collaborative resource stewardship, and cultural revitalization project facilitated by The Mountain Institute among seven Nuwuvi Nations, the U.S. Forest Service, and the U.S. Fish and Wildlife Service.