@mastersthesis {514,
	title = {Landscape Fire History and Age Structure Patterns in the Sky Islands of Southeastern Arizona},
	volume = {PhD},
	year = {2006},
	school = {University of Arizona},
	abstract = {At regional scales climate patterns (e.g., interannual wet-dry cycles) result in high spatial fire synchrony among Southwest forests. However, in the {\textquotedblleft}Sky Island{\textquotedblright} forests of southeastern Arizona spatial and temporal patterns of fire history and tree age structure at landscape levels (i.e., within mountain ranges) are relatively unknown and therefore the focus of this study. In the Santa Catalina Mountains we reconstructed the fire history on a 2,900-hectare study area with two distinct landscapes, Butterfly Peak (BP) and Rose Canyon (RC) using 2-hectare {\textquotedblleft}points{\textquotedblright} (i.e., collection areas). The RC landscape was dominated by shallow south-facing aspects and BP was dominated by steep north-facing aspects. Within each landscape, point mean fire intervals (PMFIs) were not significantly different between aspect classes. However, pooled PMFIs were significantly shorter in RC compared to BP. These results show that the fire history at any given point (i.e., 2 hectares or less) was primarily controlled by the broad-scale topography of the encompassing landscape, rather than by the fine-scale topography at that point. Using similar methods we also reconstructed the fire history on Rincon Peak, which is a small isolated mountain range with very step topography. The fire history of the 310-hectare forest area was a mixture of frequent low severity surface fires (from AD 1648 to 1763) and infrequent mixed-severity fires (from AD 1763 to 1867). This mixed-fire regime was probably due to a combination of climatic variability, the small area and rugged topography of this mountain range, and complex fuel arrangements. The distinct fire histories from these two study areas provided natural age structure experiments that indicated tree age cohorts (i.e., higher than expected tree establishment pulses) occurred during periods of reduced fire frequencies. In some instances these periods were likely caused by climatic variability (e.g., a wet and/or cool early 1800s) creating synchronous age cohorts across the region. At other times, extended fire intervals were a function of local topography (e.g., 1763-1819 in the northern half of Rincon Peak). Overall, these studies demonstrated that landscape and climatic variations combine to produce complex spatial and temporal variations in fire history and tree age structures.},
	keywords = {Renewable Natural Resources},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=1144189411\&sid=5\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Iniguez, Jose M.}
}
@mastersthesis {457,
	title = {Environmental Controls Influencing the Altitude and From of the Forest-Alpine Tundra Ecotone, Colorado Front Range},
	volume = {PhD},
	year = {1981},
	school = {University of Colorado},
	abstract = {The forest-alpine tundra ecotone of the Colorado Front Range is a dynamic vegetative belt where environmental factors vary rapidly. Under the present climatic conditions the conifer trees appear stressed and seedling establishment does not coincide with the present upper limit of tree species. With the increasing population and recreation pressure within the Front Range there is need for concern that irreversible damage may occur to the forest-alpine tundra ecotone. Meso-climatic parameters and conifer physiological responses were monitored throughout the year to determine what combinations of climate and inadequate physiological {\textquotedblleft}preparedness{\textquotedblright} result in the limitation of tree growth in the alpine. The upper limit of seedling establishment was systematically determined, and detection of a climatic change and in which direction the ecotone responded to the change were noted. In order to provide a present day inventory of the forest-alpine tundra ecotone it was mapped in detail at 1:10,000 and 1:50,000. These maps also facilitated the determination of topo-climatic influences on its distribution and provided a historical document upon which to monitor future changes. Finally, they furnished a working tool for land use planners to develop management plans. The interactions of the climate the environment and the survival of the conifer tree species within the forest-alpine tundra ecotone are indeed complex. A short, cool growing season, restricted by late-lying snow and early and late frosts, results in the tissues being unable to ripen and prepare adequately for winter hardiness. Seedlings find it impossible to establish and survive within the upper ecotone. The unpreparedness for such a harsh environment is evident during late fall when mild freezes may cause extensive damage to new growth, and during winter when many processes may weaken the tree. The winters on Niwot Ridge are long, with low temperatures, occasional days with high levels of radiation, strong winds and frozen soils. The foliage, if inadequately developed, survives only if protected by a deep snow cover. Low air temperatures, frost damage and winter desiccation appear to be primarily responsible for hindering growth in tree species within the ecotone. Of primary importance is the fact that these stress phenomena occur most often when the trees are least able to resist. The forest-alpine tundra ecotone appears at present to be under great climatic stress. The uppermost part of the ecotone is no longer successfully regenerating by seed, but rather relies on vegetative reproduction. It becomes obvious that the climate, at some time in the past, was more conducive to seedling establishment and survival. Although the ecotone has {\textquotedblleft}held its ground{\textquotedblright} for a long period of time, if it were disturbed through burning, logging, or other human activities, it would not regenerate in its present form and location. It is concluded that the ecotone, and especially the tree species limit, is a relict of a former climate and may have been established several thousand years ago.},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=753126171\&sid=5\&Fmt=2\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Bristow, Katherine Jan Hansen}
}
@mastersthesis {489,
	title = {The Stability of the Northern Canadian Tree Limit: Current Regenerative Capacity},
	volume = {PhD},
	year = {1979},
	school = {University of Colorado},
	url = {http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=751614031\&sid=5\&Fmt=1\&clientId=43922\&RQT=309\&VName=PQD},
	author = {Elliott, Deborah}
}
