@mastersthesis {591, title = {Delta-deuterium and delta-oxygen-18 in mixed conifer systems in the United States southwest: The potential of delta-oxygen-18 in Pinus ponderosa tree rings as a natural environmental recorder}, volume = {PhD}, year = {2001}, school = {University of Arizona}, abstract = {The North American Monsoon provides half of the annual precipitation in Tucson, Arizona. The other half occurs dominantly during the winter and early spring. Late spring is the transitional period to the monsoon and is characterized by high temperatures and low humidity. The reliability of this hyperarid period, the consistency of the timing of monsoon onset, and the recognition that certain high-elevation trees produce annual false latewood bands in response to this transitional period, were critical to the design of this dissertation research. I hypothesized that subannual environmental signals might be fixed in stable oxygen isotopes in cellulose from such trees. Existence of a long-term dataset of δD and δ 18 O from Tucson precipitation provided impetus for the collection of a companion dataset at a high-elevation site in the Santa Catalina Mountains north of Tucson. Trees were sampled near the precipitation collection site. The relations between the stable isotope ratios in the precipitation and in the tree cellulose were identified through extraction of water from bimonthly samples of nearby soil, tree stems and needles. Spatial consistency of the cellulose stable isotope signals was measured using tree samples from seven additional sites across the U.S. desert Southwest. Correlations between Tucson summer precipitation δ 18 O and both local and extra-regional environmental parameters resulted in the identification of the dominant monsoonal moisture source for the Tucson area. Similar correlations with the cellulose δ 18 O timeseries from the post-false latewood cellulose, supported the previous interpretations, and suggest long-term reconstructions may be possible. Correlations between the earliest cellulose δ 18 O division and extra-regional environmental parameters suggest environmental measures may be reconstructable for the cool season. Comparison of the high and low elevation precipitation δD and δ 18 O datasets yielded many baseline measures of precipitation stable-isotope dynamics in the U.S. desert Southwest. Comparison of the high-elevation precipitation stable isotope record with soil and stem water δD and δ 18 O from nearby confirmed that local trees were using dominantly deeper soil water. I noted correlations between measured needle-water stable isotope values and values calculated using a leaf-water model, but systematic departures suggest an additional unmodeled process may operate in this system.}, keywords = {Geochemistry}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=728996441\&sid=11\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Wright, William Edward} } @mastersthesis {911, title = {Restoring Ponderosa Pine Forests in the Black Hills, South Dakota}, volume = {Master of Science}, year = {2001}, pages = {50}, school = {University of Arizona}, address = {Tucson}, abstract = {

Ponderosa pine (Pinus ponderosa Laws.) forests have changed considerably during the past century, partly because recurrent fires have been absent for a century or more. In dense stands of ponderosa pine in the Black Hills of South Dakota, a layer of pine needles has replaced inderstory vegetation. I examined the disturbance history, soil seed bank, and effects of prescribed burning and overstory reduction on understory vegetation in a ponderosa pine stand in the northern Black Hills. Cessation of fires, prolific ponderosa pine regeneration, and logging led to a dense, even-aged stand with very little understory vegetation and few viable seeds in the soil seed bank. Understory vegetation did not respond to the restoration treatments the first growing season, but did respond the second growing season. Paucity of viable seeds in the soil seed bank does not appear to constrain recruitment of understory vegetation in dense ponderosa pine forests of South Dakota.

}, keywords = {black hills, fire history, overstory, pinus ponderosa, ponderosa pine, prescribed fire, restoring, soil seed bank, south dakota, stand age, understory}, author = {Wienk, Cody Lee} } @mastersthesis {696, title = {delta(13)C and stomatal density variability in modern and fossil leaves of key plants in the western United States}, volume = {PhD}, year = {1999}, school = {University of Arizona}, abstract = {During the last deglaciation, 15,000 to 12,000 calendar years ago, global warming and wholesale shifts in regional precipitation patterns produced dramatic changes in vegetation worldwide. Paleobotanical records, namely pollen and macrofossils, have been used not only to reconstruct shifts in plant distributions and abundances, but also to quantify changes in temperature and precipitation amounts or seasonality. In addition to climatic change, during the full glacial period atmospheric CO 2 values had dropped 30\% to 200 ppmv compared to the Holocene, preindustrial value of 280 ppmv. Hypothetically, variations in atmospheric CO 2 affect plant water-use efficiency (carbon gained to plant-water transpired) and thus may have modulated vegetation response as climates change. The studies incorporated in this dissertation focused upon carbon isotope and morphological changes in leaves of key functional groups. The studies concentrated on plant species that are abundant in the fossil record and comprise major floral components of past and present vegetation. Key findings include: (1) that shifts in δ 13 C in modern populations along steep environmental gradients seldom exceeds inter-plant variability at a given site, (2) inter-plant and intra-site variability in modern and historic herbarium collections of the C 4 halophytes Altriplex canescens and A. confertilfolia and packrat midden macrofossils of A. canescens excludes their use as a reliable proxy for atmospheric δ 13 C, (3) calcium-oxalate crystals are common component in plant tissue and can have a significantly different δ 13 C value that increases inter-plant variability, especially in C 4 plants such as Atriplex canescens and A. confertifolia , (4) carbon isotope and stomatal density/index measurements of macrofossils from packrat middens show species specific adaptation in ecophysiological processes as atmospheric CO 2 rose from the full glacial, and (5) the greatest adaptation to low atmospheric CO 2 during the last ice age was in the C 3 species and that C 4 and CAM plants showed few changes in their discrimination against 13 C or in the number of stomata on their leaf surfaces.}, keywords = {Atriplex, Carbon-13, Fossil leaves, Stomatal density}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=731687391\&sid=11\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Peter van der Water} } @mastersthesis {548, title = {Carbon Isotopic Variations in 7 Southwestern U.S. Plants from Herbarium Collections of the Last 150 Years}, volume = {MS}, year = {1997}, school = {University of Arizona}, keywords = {Renewable Natural Resources}, author = {Pedicino, Lisa Christina} } @mastersthesis {585, title = {Reconstruction of historical fire regimes along an elevation and vegetation gradient in the Sacramento Mountains, New Mexico}, volume = {MS}, year = {1997}, school = {University of Arizona}, abstract = {The purpose of this study was to reconstruct historical fire regimes along an elevation and vegetation gradient in the Sacramento Mountains, NM. I cross-dated fire-scarred specimens to reconstruct the fire history within two mixed-conifer, four ponderosa pine, and two pinon-juniper stands. Prior to Euro-American settlement, historical fire intervals were estimated at 6 years in ponderosa pine, 10 years in mixed-conifer, and 27 years in pinon-juniper forests. To evaluate whether Native Americans may have influenced historical fire regimes, I cross-dated scars from peeled trees found within the study area. Comparison between scar dates, historical records, and variations in fire frequencies did not show a regional effect on historical fire regimes by Mescalero, but suggested that they may have had a local impact on fire frequencies of the late 1700{\textquoteright}s. Following Euro-American settlement (ca. 1880) fire was nearly absent from the study area due to livestock grazing and fire suppression.}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=738180921\&sid=4\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Wilkinson, Margot Carolina} } @mastersthesis {590, title = {Tsegi Canyon Cliff Ruin Beam Coring Project: A Dendrochronological Analysis of Six Sites in the Tsegi Canyon Complex, Northeastern Arizona}, volume = {MA}, year = {1997}, school = {University of Arizona}, keywords = {Archaeology}, author = {Wright, William Edward} } @mastersthesis {663, title = {The archaeological measures and social implications of agricultural commitment}, volume = {Phd}, year = {1996}, school = {University of Arizona}, abstract = {This is a case study of the causes and consequences of the shift from a forager-farmer adaptive strategy to village agriculture in the Southwest{\textquoteright}s mountainous Transition Zone. The earliest inventions and adoptions of agriculture have attracted a steady stream of archaeological research, but far less attention has been given to the subsequent change to dietary dependence on and organizational dedication to food production--agricultural commitment. Although there is little doubt that the Southwest{\textquoteright}s large villages and small towns were committed to successful farming, methodological and conceptual problems have impeded archaeological analyses of the ecological and evolutionary implications of this revolutionary shift in how people related to the world and to one another. The rapid and radical change that occurred in the Transition Zone{\textquoteright}s Grasshopper Region during the late AD 1200s and early 1300s provides a high resolution glimpse at the processes and products of agricultural commitment--notably increasing reliance on farming and the development of permanent towns and institutionalized systems for resource and conflict management. The model proposed for the Grasshopper Region involves population immigration and aggregation leading to increased agricultural reliance and related changes in settlement and subsistence ecology as well as social organization. Critical issues involve the ecological, social, and theoretical significance of these shifts, the methodological capacity to track dietary, settlement, and organizational change archaeologically, and the implications for understanding Western Pueblo social development in terms of seeing the Grasshopper occupation as an experiment in agriculturally-focused village life.}, keywords = {Fort Apache Indian Reservation, Mogollon culture, White Mountain Apache Tribe}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=739663551\&sid=2\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {John Welch} } @mastersthesis {589, title = {Climate variability in the southwestern United States as reconstructed from tree-ring chronologies}, volume = {PhD}, year = {1996}, school = {University of Arizona}, abstract = {The primary goal of this research is to gain a better understanding of the spatial and temporal relationships between atmospheric circulation features and winter climate variability in the southwestern United States, and to investigate the variations in these relationships over the past three centuries. A set of six circulation indices is compiled that describes circulation features important to winter climate variability in this region. This set includes pre-existing indices such as the SOI and a modified PNA index, as well as regionally-tailored indices. A network of 88 tree-ring chronologies is then used to reconstruct the indices and the regional winter climate variables: numbers of rainy days (a variable not previously reconstructed with tree rings) and mean maximum temperature. Analyses suggest that three types of circulation features have influenced winter climate in the Southwest over the past three centuries. Although ENSO-related circulation patterns have been an important factor, especially in the 20th century, circulation patterns featuring a southwestern low appear to be as important if not more important to climate in some time periods. Results suggest that low frequency variations in atmospheric circulation patterns have occurred over the past three centuries and have had spatially and temporally varying impacts on winter climate in the Southwest.}, keywords = {Paleoecology}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=739718221\&sid=24\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Woodhouse, Connie Ann} } @mastersthesis {661, title = {Late Quaternary vegetation history of the southern Owens Valley region, Inyo County, California}, volume = {Phd}, year = {1996}, school = {University of Arizona}, abstract = {This study analyzes the pollen, spores, and algae in the upper 90 m section of a mostly continuous, well dated, 323 m core (OL-92) from Owens Lake, southeastern California. The entire core has produced a paleoclimatic record for the past $\sim$800 ka. The 90 m interval dates from $\sim$9 ka to $\sim$151 ka beginning with the penultimate glaciation and ending during the termination of the last glaciation. The record shows high amplitude fluctuations in the abundances of pine, juniper, saltbush, sagebrush, chenopods/amaranths, and Ambrosia-type pollen. High percentages of juniper pollen with low percentages of desertscrub pollen during the intervals $\sim$150 ka to $\sim$120 ka and 73 ka to $\sim$20 ka alternate with low juniper pollen and relatively high percentages of desertscrub and oak pollen during the intervals $\sim$118 ka to $\sim$103 ka and $\sim$18 ka $\sim$10 ka and into the Holocene. Sagebrush pollen varies with juniper pollen but has a tendency to lead it in time. Pine and fir pollen tends to vary inversely with juniper over the long term. These trends are interpreted as vegetation change in response to glacial-interglacial cycles: During cold-wet glacial climates there was a downslope expansion of juniper woodland and sagebrush scrub, contraction of Sierra Nevada mixed conifer forest, and displacement of warm desertscrub, suggesting average temperature and precipitation departures from modern values ranging from $-$2$\sp\circ$C to $-$6$\sp\circ$C and from +100 mm to +350 mm. Conversely under warmer and drier interglacials warm desert shrubs expanded their range in the lowlands, juniper and sagebrush retreated upslope, and the Sierran forests expanded. Estimated average temperature and precipitation departures from modern values ranged from $-$0.5$\sp\circ$C to +3.7$\sp\circ$C and +13 to $-$26 mm. Comparison of the pollen spectra spanning the penultimate and ultimate glacial maxima shows the former to have been longer and more intense, in accord with the Sierra Nevada glacial record. Similarly, the higher abundances of Ambrosia pollen during the last interglaciation, compared to the Holocene, indicate warmer temperatures in the former. The presence of high oak percentages also during the last interglaciation suggest an expansion of the summer monsoon. Finally, the match of the juniper curve with the marine oxygen isotope chronostratigraphy suggests a link between vegetation change in the southern Owens Valley and global climate.}, keywords = {climate, glaciation, global change, juniper, pine, sagebrush, saltbrush}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=739577661\&sid=22\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Wallace Woolfenden} } @mastersthesis {588, title = {Synoptic Dendroclimatology in the Upper Marmada River Basin: An Exploratory Study in Central Asia}, volume = {MS}, year = {1996}, school = {University of Arizona}, abstract = {Dendrochronological analysis of teak (Tectona grandis) collected from stumps in the Malpathar National Reserved Forest of the upper Narmada River Basin in central India has the potential to provide continuous and long-term information about changes in both the local climate of the Malpather National Reserved Forest site and the Indian monsoon circulation{\textellipsis}}, author = {Wood, Michelle Lee} } @mastersthesis {695, title = {Modeling prehistoric climatic variability and agricultural production in southwestern Colorado: A GIS approach}, volume = {PhD}, year = {1990}, school = {Washington State University}, abstract = {A model with high temporal and spatial resolution has been developed for a 1816 km$\sp2$ area of southwestern Colorado to examine the potential effects of past climatic variation on dryland maize agriculture and sustainable population during the late Mesa Verde Anasazi occupation of the area (A.D. 901-1300). The data generated by the model are used to evaluate a question of long standing in the Northern Southwest: whether climatic variability was severe enough to disrupt agriculture and promote the abandonment of the Northern San Juan Region toward the end of the 13th century. The model incorporates techniques and data sets that have not been used together before. Long regional dendroclimatic records are used to retrodict 1070 years (A.D. 901-1970) of June Palmer Drought Severity Indices (PDSI)--measures of stored soil moisture--for area-specific soils. Reconstructed PDSIs are reexpressed in terms of their local equivalent in potential maize yield. The integration, quantification, and visual display of these productivity values are coordinated through geographic information systems (GIS) technology. The method results in the production of (1) annual maps depicting the variable character of the potential agricultural environment and (2) annual values for total maize productivity, which can be translated into the population size and density that can be potentially supported on that yield. From these, multiple year estimates of a sustainable population or carrying capacity are made. The results indicate that there was always enough productive land somewhere in the study area to support thousands of persons (e.g., 31,363 persons or 21 persons/km$\sp2$ minimum in the 1470.36 km$\sp2$ study area over the 400-year period), even in the documented dry times of the middle 12th and late 13th centuries. It would seem, therefore, that climatic variability was never so extreme in the Mesa Verde area that decreased agricultural production can be cited as the sole or even primary cause of the 13th century depopulation of the region. }, keywords = {Anasazi}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=747133751\&sid=7\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Carla Van West} } @mastersthesis {905, title = {A Dendrochronological Study of the Great Salt Lake Basin}, volume = {Master of Science}, year = {1989}, note = {

Please contact the Laboratory of Tree Ring Research to view this thesis.

}, month = {03/1989}, pages = {77}, school = {University of Utah}, address = {Salt Lake City}, abstract = {

To date, no tree-ring chronologies have been generated for the Great Salt Lake basin. There is evidence of a winter air mass boundary across this area. Since the region receives a precipitation maximum in the winter and spring, information about boundary location variability would be useful. Tree-ring widths may be related to climatic variables and provide a record of past climate.

Four tree-ring chronologies in the four corners of the Great Salt Lake basin were generated using standard dendrochronological techniques. Precipitation and temperature data for the area were regionalized and tree-ring indices were correlated with regional temperature seasons and with precipitation regions and seasons. The chronologies were factor analyzed for the period of common growth, 1593-1985, and broken down into seven overlapping one hundred-year periods.

During the period for which there are weather records, tree growth in the northwest site was correlated with temperature variables, while in the other three sites, tree growth was mostly correlated with precipitation. The results of the factor analysis of the chronologies for the seven time periods were consistent with the correlation results. The results also indicate a similar pattern of variation of growth for the time periods of 1593-1650 and 1825-1940.

The four Great Basin chronology sites are located in a unique region and may be used to learn about climatic variability in this area.

}, keywords = {climatic variability, dendrochronology, dendroclimatology, Geography, great salt lake basin, indices, precipitation, salt lake, temperature, tree ring}, author = {Connie Woodhouse} } @mastersthesis {706, title = {Culture change and the Navajo Hogan}, volume = {Phd}, year = {1985}, school = {Washington State University}, abstract = {The Navajo tribe has been subjected to acculturation pressures since its arrival in the American Southwest in the 1500s. The pressures came first from indigenous Pueblo groups, these were succeeded by pressures from the Spanish, Mexicans, Utes, U.S. military, and other Euroamerican local populations. The Navajo response to the pressures of acculturation in both the economic and religious spheres of life is manifested in the Navajo house or hogan. The hogan serves as both a sacred and secular structure. Some features of hogan construction such as shape and doorway orientation have strong symbolic associations, and alterations in their form thus reflect fundamental shifts in religious orientation. Other features of hogan construction such as the use of power tools or milled lumber, while changing the appearance of the structure, do not have strong symbolic associations and thus are not indicative of a similar shift away from traditional Navajo culture. Instead, these features represent a Navajo incorporation of items from the dominant culture that are most useful in easing the hardships of traditional life. Habitation structures from two areas of Arizona illustrate this trend. Over 500 structures from the remote, conservative and until very recently, unacculturated area of Black Mesa are compared with over 200 structures from the substantially more acculturated region of the Defiance Plateau. The difference in the chronology of housing construction techniques between the two areas is striking. Influences from the dominant culture, including a shift away from traditional houses, are evident in the late 1800s on the Defiance Plateau. Conversely, on Black Mesa, these same trends do not appear until the 1970s and 1980s. Architecture is composed of both a technological and an expressive element. This marriage of two aspects of culture in one place--housing--is an important locus of information for anthropologists. Analysis of changing construction methods and morphology provides a physical manifestation of changes documented in other areas of the cultural system. }, keywords = {Arizona}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=753300051\&sid=19\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Miranda Warburton} } @mastersthesis {575, title = {Allometric Analysis of Plant Growth in Woodland Communities}, volume = {PhD}, year = {1980}, school = {Utah State University}, abstract = {Several allometrically-based equations were derived to describe the changes and the similarities in the structure and shape of semiarid woody plants that occur with growth. The derivations utilized general hypotheses based on the assumption that one of the principal purposes of a plant{\textquoteright}s structure is the efficient support and distribution of its leaves. Results from analyses of plant branching systems were used to derive allometric relationships between selected variables of plant size and shape. A close correspondence often occurred between the parameters resulting from the derivations and those that resulted from empirical analyses of field data. The variability of some relationships was found to be linked to increasing tree dominance, and/or increasing tree size. Changes potentially linked to differing site quality were also observed for some relationships. Other relationships remained relatively uniform over a range of successional stages and also potentially uniform over a range of site quality. The analyses revealed important crown structure and foliage distribution similarities, as well as differences, between the plant species studied. In general, large plants were often less variable, relative to their size, than small plants. Each species also has a relatively consistent leaf distribution within its crown. A number of implications and applications of the results to plant sampling and vegetation analyses were discussed. This includes discussions of the need for, and possible means of obtaining, adequate methods of determining site quality for woody plant communities in non-timber producing regions. Overall, the analyzed allometric relationships resulted in a generalized working model of plant growth and development, particularly for the changes in size, shape and biomass that occur with growth.}, keywords = {Ecology}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=749271331\&sid=1\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD}, author = {Tausch, Robin} } @mastersthesis {586, title = {Relationships Among Climate, Tree-Ring Widths and Grass Production on the Santa Rita Experimental Range}, volume = {MS}, year = {1976}, school = {University of Arizona}, abstract = {A relationship between tree-ring widths from a site in the Santa Rita mountains and yearly perennial grass production on pasture 1 of the Santa Rita Experimental Range is investigated{\textellipsis}}, author = {Winter, C. Larrabee} } @mastersthesis {587, title = {Paleoecology and the Prehistoric Maya: A History of Man-Land Relationships in the Tropics}, volume = {MS}, year = {1974}, school = {University of Arizona}, abstract = {A series of modern soil samples were collected in lowland Guatemalan rainforest, savannah, milpa, and lakeside association or pollen analysis{\textellipsis}}, keywords = {Geoscience}, author = {Wiseman, Fredrick Matthew} } @mastersthesis {584, title = {Dating the Temporal Limits of Climatic Episodes During the Holocene}, volume = {PhD}, year = {1971}, school = {University of Wisconsin}, keywords = {Meterology}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=758273691\&sid=8\&Fmt=1\&clientId=43922\&RQT=309\&VName=PQD}, author = {Wendland, Wayne Marcel} } @mastersthesis {583, title = {Tree-Ring Dating and Archaeology in South Dakota}, volume = {PhD}, year = {1968}, school = {University of Arizona}, abstract = {In 1964 a study of the feasibility of applying the methods of tree-ring research to wood collected in South Dakota was undertaken by the Laboratory of Tree-Ring Research, University of Arizona{\textellipsis}}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=757411981\&sid=5\&Fmt=1\&clientId=43922\&RQT=309\&VName=PQD}, author = {Weakly, Ward Fredrick} } @mastersthesis {592, title = {Some Ecological Studies on Bristlecone Pine in the White Mountains of California}, volume = {PhD}, year = {1963}, school = {University of California}, abstract = {Bristlecone pine, Pinus aristata, was studied in the White Mountains of California. The climate is dry, with annual precipitation in the bristlecone zone averaging 12 to 13 inches. The trees are found in a zone from approximately 9,500 feet to 11,500 feet elevation. Three geologic substrates are widely exposed in the bristlecone zone: dolomitic limestone, sandstone and granite. Vegetation was sampled on these substrates, using line transects. Bristlecone pine is restricted principally to dolomite. Sagebrush, Artemisia tridentate and A. arbuscula, is distributed in a complementary pattern, restricted largely to sandstone and granite. Bristlecone pine and sagebrush constitute the bulk of the vegetation. Dolomite in the White Mountains is a nearly white rock, whereas sandstone and granite are dark. The white rock reflects more solar radiation than do the other substrates, and as a result the dolomite soil averages several degrees centigrade cooler than sandstone soil. This lower temperature acts as a moisture conserving mechanism on dolomite, delaying soil drought. Dolomite also has higher moisture capacity than sandstone and granite. Through use of an infrared gas analyzer, the effect of soil drought on photosynthesis of bristlecone pine was measured. Photosynthesis was depressed by soil drought in the same range as the attained in field soils during dry periods in summer. Photosynthesis of sagebrush as a function of soil drought was also measured. Sagebrush was found more tolerant of drought than bristlecone pine. Drought tolerance may be one factor contributing to maximum development of bristlecone pine on dolomite, and of sagebrush on sandstone and granite. Bristlecone pine reaches maximum development on north slopes, and sagebrush reaches maximum development on south slopes. This supports the conclusion that drought tolerance is a decisive factor in determining substrate-oriented distribution patterns. Sagebrush and bristlecone pine seedlings both grew poorly on dolomite in pot trails. It was suggested that the high pH of dolomite soil, averaging 8.1, results in low mineral nutrient availability, and that sagebrush, with its shallow root system, is less efficient in obtaining mineral nutrient requirements than is the deep rooted pine. Photosynthesis measurements demonstrated that bristlecone pine is tolerant of shading. Furthermore, it was shown by growth measurements that bristlecone pine seedlings grow much more slowly than sagebrush seedlings. These findings indicate that the pine seedling would not succeed in the shade of sagebrush seedlings, another response that contributes to the substrate-oriented distribution of bristlecone pine. Maximum elevation of bristlecone pine is the same on all substrates, and was found to be limited by air temperature during the growing season. Minimum elevation is lower on dolomite than on the other substrates, and is under the control of soil drought. Attainment of great age was shown to be associated with death of the tree trunk around most of its circumference. Lack of krummholz at tree line shows both genetic resistance to deformation, and the influence of a very dry climate.}, url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com.ezproxy2.library.arizona.edu/pqdweb?did=763335561\&sid=2\&Fmt=1\&clientId=43922\&RQT=309\&VName=PQD}, author = {Wright, Robert Dennison} }