@mastersthesis {653,
	title = {Aspen: Ecological processes and management eras in northwestern Wyoming, 1807--1998},
	volume = {PhD},
	year = {2000},
	school = {University of Arizona},
	abstract = {Quaking aspen stands in many areas of the intermountain west are currently dominated by older (>100 year) age classes and may be in decline. The goals of my research are to: (1) place current observations of aspen decline into context by using historical and ecological data to investigate the interaction of fire, ungulate browsing, climate and human institutions in the regeneration of aspen stands over the last two centuries; (2) evaluate the challenges and limitations associated with using ecological history for management of aspen and other systems; and (3) compare current and historical aspen regeneration across three elk winter range areas in the intermountain West.

Based on results from stand age structures, aspen regeneration in the Jackson Valley has occurred episodically since 1830, with three major periods of regeneration: 1860-1885; 1915-1940; and 1955-1990. These multi-decadal episodes of aspen regeneration are related to similar variability in precipitation, where above average periods of annual precipitation are associated with aspen regeneration. However, significant levels of aspen regeneration have only coincided with low or moderate elk population estimates and fewer aspen have regenerated than expected when elk populations are high ( X 2 = 59.92, p < 0.0001). Current aspen reproduction, though minimal, is strongly affected by elk browse with percent browse significantly higher in elk winter range than outside of elk winter range (p = 0.051). Though extensive or frequent fires may have maintained aspen communities during the pre-settlement era, current management controlled fires have not affected aspen sucker density.

The influence of multiple interacting processes and drivers in the Jackson Valley suggests that reconstructing past ecosystems as benchmarks for ecological management should be considered carefully. Given future environmental variability, reconstructions of past systems should focus on ecological relationships rather than on single states or processes.

Comparison of aspen in the three elk winter range areas indicates that heavy browsing by elk populations has had a strong influence on episodes of aspen regeneration for the last 150 years in all three elk winter ranges. However, elk are not having strong impacts on aspen outside of elk winter range.
},
	keywords = {Ecology, Geography, Paleoecology},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=731957311\&sid=11\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Amy Hessl}
}
@mastersthesis {559,
	title = {Dendroclimatology in the San Francisco Peaks region of northern Arizona, USA},
	volume = {PhD},
	year = {2000},
	school = {University of Arizona},
	abstract = {Millennial length temperature and precipitation reconstructions from tree rings are developed for the northern Arizona region and applied to questions regarding the nature of the cultural-environmental interface in the northern Southwest, the role of explosive volcanism as a forcing mechanism in temperature variability, and the state of late 20th century climate compared to the range of natural variability of the past. A 2660-year long bristlecone pine tree-ring chronology from high elevation in the San Francisco Peaks of northern Arizona is calibrated with instrumental annual mean-maximum temperature data to reconstruct temperature. Three 1400-year long lower elevation tree-ring chronologies, developed from both living trees and wood from archaeological sites on the Colorado Plateau, are calibrated with instrumental precipitation data (October-July) to reconstruct precipitation. The juxtaposition of these two reconstructions yields paleoclimatic insights unobtainable from either record alone. Results include the identification of wet, dry, cool, and warm intervals and the identification of periods of high and low variance in temperature and precipitation. Population movement into the Flagstaff area in the second half of the 11th century is attributed to relatively warm wet conditions. The role of temperature decline in the 13th century merits additional consideration in the prehistoric regional abandonment of the Four Corners area. Many of the reconstructed cold periods are linked to explosive volcanism. The second half of the 20th century is the warmest in the period of record, and extremely warm/wet conditions have persisted since 1976.},
	keywords = {Paleoecology},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=731919721\&sid=18\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Salzer, Matthew W.}
}
@mastersthesis {500,
	title = {Sierra Nevada Tree Rings and Atmospheric Circulation},
	volume = {PhD},
	year = {1998},
	school = {University of Arizona},
	abstract = {<p>The primary objective of this research is to investigate relationships between extremes in central Sierra Nevada tree growth, temperature and precipitation and winter and summer atmospheric circulation. Using existing Sierra Nevada chronologies, I developed two mean chronologies for the period of overlap between instrumental and tree-ring records (1900-1987), one for giant sequoia (Sequoiadendron giganteum) and one for treeline pines (Pinus balfouriana, Pinus albicaulis) and selected the highest and lowest quintiles of tree growth as extreme years. For these years, I constructed and analyzed maps of composite anomalies for the following climatic data: tropospheric pressure (SLP, 700 mb, 500 mb), storm track (positive vorticity advection [PVA], a variable not previously used in dendroclimatology), temperature, precipitation, and snow (a variable often assumed have the same effects on growth as winter precipitation). Results suggest that extreme growth in these trees is associated with distinct patterns of winter atmospheric circulation and snow depth that are consistent with instrumental studies for the Western U.S. The storm track and snow analyses, seldom used in dendroclimatology, added substance to inferences based on analyses of tropospheric and surface climate parameters. This study shows the strong potential for reconstruction of these variables using Sierra Nevada trees. Synthesis of these results suggests that sequoia exhibit low growth during years with meridional winter and summer circulation, winter storms primarily occluded in the Gulf of Alaska, and low snow depth; sequoia exhibit high growth during years with low winter pressure in the north Pacific, long duration storms, a SW-NE oriented storm track entering North America at the California-Oregon border, high snow depth and zonal summer flow. Treeline pines exhibit low growth during years with enhanced ridging over the eastern Pacific, cool, short duration winter storms along a northern track, low snow depth and high east Pacific summer SLP; these pines exhibit high growth during years with warm, long duration winter storms following a southern track, a quasi-PNA atmospheric circulation pattern, average snow depth and a northeastward displaced summer subtropical high. Evidence presented herein suggests that variation in extreme treeline pine growth tracks low frequency changes in north Pacific atmospheric circulation.</p>},
	keywords = {Paleoecology},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=733009441\&sid=28\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Garfin, Gregg Marc}
}
@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 {451,
	title = {Spatial and Temporal Reconstruction of Twentieth-century Growth Trends in a Naturally-seeded Pine Forest},
	volume = {PhD},
	year = {1994},
	school = {University of Arizona},
	abstract = {<p>This research uncovered growth trends from 1920 to 1990 in a stand of south-western ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. scopulorum), and investigated the role of climate and competition in shaping the observed trends. I focused on a 800 x 400-m permanent plot maintained by the U.S. Forest Service since 1920 near Flagstaff, Arizona. Temporal growth trends were quantified by size class using a mixed linear model applied to forest inventories, repeated at 10-year intervals. Tree density and stand basal area increased from 1920 to 1990, but growth rates of individual trees declined regardless of size class. Growth of large pines, whose density increased slightly, declined more than that of small pines, whose density almost tripled. I argued that competition for resources reduced growth rates of large trees more than those of small trees. Geostatistical analyses showed that, from 1920 to 1990, stem size was spatially autocorrelated over distances no greater than 30 m, a measure of average patch diameter. Tree density increased by increasing the number of pine groups rather than their horizontal dimension. Increased tree crowding corresponded to lower average, variance, and spatial dependence of individual growth rates. Since growth variation was less related to inter-tree distance at higher tree densities, density-dependent limitation of tree growth did not necessarily correspond to distance-dependent growth rates. No significant trend from 1910 to 1990 was found in climatic variables computed from daily meteorological records. Dendroclimatic analyses showed that climate-tree growth relations had not significantly changed over the twentieth century. Annual growth of both large and small pines was positively related to winter snowfall and to July monsoon rainfall. Periodic basal area increment obtained from dendrochronological data revealed that forest inventories over-estimated growth rates, especially for small pines. On the other hand, tree-ring chronologies developed using different standardization options showed different temporal trends. Repeated forest inventories quantified growth of individual trees and of the entire stand, but integrated bark and wood increment. Dendrochronological data had superior temporal resolution and accuracy, but their limited spatial coverage hindered representation of growth trends for the entire stand.</p>},
	keywords = {Paleoecology},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=740900561\&sid=29\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Biondi, Franco}
}
