@mastersthesis {910,
	title = {Stand Replacing Fire History and Aspen Ecology in the Upper Rio Grande Basin},
	volume = {Master of Science},
	year = {2003},
	pages = {94},
	school = {University of Arizona},
	address = {Tucson},
	abstract = {<p>Dendroecological techniques were applied to reconstruct stand-replacing fire history in mixed conifer and spruce-fir forests in northern New Mexico and southern Colorado. Stand-replacing fire dates with annual accuracy and precision were determined using four lines of evidence for each of twelve sites within a 75,000 square kilometer area. The four lines of evidence were: (1) aspen inner-ring dates, (2) conifer death dates, (3) tree-ring width changes, or other morphological indicators of injury, and (4) fire scars. The annual precision of dating allowed the identification of significant synchrony of stand replacing fires among the 12 sites and regional surface fire events previously reconstructed from the large network of fire scar collections in the Southwest. Nearly all of these synchronous stand-replacing and surface fire years coincided with extreme droughts. This suggests that stand-replacing fire activity occurred primarily when drought conditions allowed fires to ignite and spread within these high elevation forests and/or for the spread of surface fires between lower and upper elevations. Fifty percent of reconstructed stand-replacing fires pre-dated large-scale Euro-American settlement in this region. This may suggest that land use practices (such as logging and mining) were not as important in promoting stand-replacing fires in these study sites, as compared with other areas in Colorado.</p>},
	keywords = {aspen, basin, colorado, conifer, dendrochronology, dendroecology, Ecology, fire, fire history, new mexico, rio grande, spruce fir, stand replacing, tree ring},
	author = {Margolis, Ellis Quinn}
}
@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 {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}
}
@article {644,
	title = {Evidence of Climatic Effects in the Annual Rings},
	journal = {Ecology},
	volume = {1},
	year = {1920},
	keywords = {annual rings, climate, climatic, Douglass, Ecology, effect, effects, evidence, historic, rings, tree},
	author = {Douglass, A.E.}
}
