Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 20-23). Also available on the World Wide Web.

Thesis (Ph.D. - Geosciences)--University of Arizona. / Includes bibliographical references (leaves 248-263).

The assumption that each latewood ring in trees represents one year of growth was tested for Utah juniper (Juniperus osteosperma) and pinyon pine (Pinus edulis). Ring characteristics and growth rates were evaluated for 72 years of growth following scars of consistent date on all trees sampled. Errors in age and growth rate estimates based on ring counts were evaluated. Potential variation among observers was accounted for. Average error in ring counts was lowest when rings were counted on the fastest-growing portions of each cross-section. Errors for more than 40% of the junipers exceeded 10 percent with about half of the trees with more rings and half with less rings than actual years. Pinyons rarely had more rings than years and only 5% of the trees were missing more than 10% of the 72 annual rings. Percentage errors in growth rate estimates based on ring counts were similar to ring count errors for both species. Assigning junipers to age classes based on ring counts also can lead to error in assumed ages of trees. Assuming that ring count error for each tree for the 72 year period studied approximates potential error over the life of each tree, more than half of junipers older than 250 years would be assigned to the wrong age class when using 50 year age classes. Number of rings in junipers was highly correlated with growth rate. Competition from surrounding trees explained as much as 53% and 40% of the variation in growth rates of junipers and pinyons respectively. Relating growth rates and ring counts to ordinations of stand, site and soil characteristics indicated that trees with relatively fast growth rates or trees with the most rings tended to occur on gentle, north to northeast aspects with relatively better- developed soils. However, stand competition often had an overriding influence on growth. Presence of Koelaria pyramidata in the understory was generally an indicator of relatively favorable growing conditions for junipers. Results suggest the need for more caution in the use of ring counts for estimating ages or growth rates of Utah junipers and pinyons than has generally been used in the past, especially when drawing conclusions about specific individuals.

No description available.

I assessed the paleoclimatic significance of SD values of pition pine (Pinus edulis and P. monophylla) cellulose nitrate (cn) by developing, testing and applying deterministic and empirical models, in the context of the soil-plant-atmosphere continuum. Stable isotope values of precipitation, soil water, xylem sap, leaf water, atmospheric vapor, annual and sub-annual samples of tree-ring and needle cellulose, and climatic parameters, were measured along a gradient of decreasing summer rain in the southwestern U.S. Stable isotope composition of sap indicated depth of moisture extraction. Over the growing season in New Mexico and Arizona, where monsoon rains are important, trees shifted their water use to shallower depths. In Nevada, where summer rain is scarce, trees shifted to deeper moisture late in the growing season. Evaporation altered δD and δ¹⁸O values of precipitation inputs to soil. Only after heavy monsoons did soil water and sap isotopically resemble recent precipitation. Average precipitation δD values set the baseline for δD(cn). values at each site, but interannual variations in relative humidity and precipitation amount altered wood and leaf δD(cn) values, via leaf water effects. Leaf water (1w) was evaporatively enriched by seasonal moisture stress. δD(1w). and δ¹⁸O(1w) values were strongly correlated with relative humidity on a seasonal basis, but not on a diurnal basis. Measured δ¹⁸O(1w) values fit a steady-state model, with an offset attributable to relative humidity. Measured δD(1w) values were more depleted than predicted by the model, suggesting leaf water - organic matter isotopic exchange. Biochemical fractionation (ε(B)) of hydrogen isotopes between leaf water and cellulose was inversely correlated with relative humidity. Empirical models based on linear regressions demostrated significant correlations between δD(en) values and precipitation seasonality. An El Nirio-Southern Oscillation signal (wood δD(en) values inversely related to winter precipitation amount) was found in New Mexico and Arizona. A summer rain signal (leaf δD(en) values inversely related to summer humidity) was found at all sites. δD(en) values of pirion needles in packrat middens from Sevilleta LTER, New Mexico, suggest that late Pleistocene summers were as wet as today's, and/or that storm tracks could have shifted, bringing in more tropical moisture than currently.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "May 2006." Includes bibliographical references (leaves 72-76). Online version available on the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "May 2005." Includes bibliographical references (leaves 26-29). Online version available on the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "December 2007." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references (leaves 80-85). Online version available on the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 23-26). Online version available on the World Wide Web.