Achieving societal well-being goals is inextricably linked to the preservation of many ecosystem functions. This dissertation adopts a plant lens, to contribute to our understanding of sustainable ecosystem functioning. Specifically, it sheds light on some plant physiology, phenology, and ecology processes, which matter for sustainable development: tree growth response to high temperatures, annual fluctuations in the timing of plant flowering, and ecological benefits of crop diversity that translate into economic returns. In addition, it illustrates how large-scale data proxies can be used to document large scale patterns that arise from individual plant processes. Chapter 1 documents a new methodology for estimating tree-level temperature response curves, using tree ring data and a degree-day framework. It uses those curves to document harmful impacts of high temperatures for tree growth across the US, and shows that there is limited acclimatization, but some adaptation to those high temperatures in a sample of climate sensitive and long-lived trees. Chapter 2 shows that satellite imagery and deep learning tools can be leveraged, to monitor interannual variations in the timing of plant flowering at large scales. It documents the predictive performance of two models: one adapted to monitoring crop flowering, the other adapted to monitoring shifts in the onset of spring flowering. Finally, chapter 3 highlights remaining gaps between empirical evidence of crop diversity benefits, and portrayal of those benefits in economic models of optimal crop diversity choice. Together, these chapters illustrate that bridging scales and disciplines is a difficult task, although it is necessary for understanding the sustainability of the human environmental footprint.

A study ot discordant variation in populations of Purshia tridentata, Purshia glandulosa, and Cowania Stansburiana has disclosed that introgressive hybridization can be expected whenever these species come in contact with each other. The introgression is not only of one pure species into that of another, but is also of introgressed populations into other introgressed populations and of pure populations into introgressed populations. Evidence was found showing that in all probability Purshia glandulosa is a stabilized segregant derived from introgressed populations. Evidence was also found and presented to show that introgression is responsible for the recent acquisition of stalked hypanthium glands by many populations of Purshia tridentata .

A total of 28 burn areas, that varied in age from 3-100+- years, were analyzed in a study of succession following fire, in the pin yon-juniper woodlands of west central Utah. Data were collected by means of the line-point and quadrat methods. These data were subjected to a multiple regression analysis. Canopy cover, basal area (sq. ft./acre) and density (trees/acre) of juniper were highly correlated with age of burn. Percentage dead sagebrush was found to be positively correlated with density of junipers. The stages of succession following fire began with weedy annuals, that reached a peak within 3-4 years. Juniper woodlands are well developed 85-90 years following fire. Intermediate stages of succession varied, but followed a general pattern of perennial grasses, perennial grasses-shrubs and perennial grasses-shrubs-trees. Tree height and stem diameter are positively correlated with age of Utah juniper. Thirty-three years is the average minimum age at which Utah juniper produce seed.

The purpose of this thesis is to present the results of a morphological investigation of the megagametophytes of two species of Fritillaria. The author has attempted to present the data in sufficient detail to clearly picture the significant features in the histories of this gametophyte generation without unnecessary repetition. The data are presented as their chronological sequence dictates.

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The occurrence of weed species with hemp significantly affects the development and yield of hemp (Cannabis sativa L.). Three experimental studies were conducted to examine whether weed species like Amaranthus tuberculatus L., Eleusine indica L., Ipomoea spp. L. suppress the growth of hemp. The results show that the presence of these weed species was responsible for the reduced growth of hemp in terms of height, stem diameter number of leaves except when some weed densities were reduced with a grass-specific herbicide, but the weed species did not have any association with the N (nitrogen) and C (carbon) assimilation of hemp. Additionally, utilizing a de Wit replacement series design, a greenhouse study investigated the competitiveness of the two hemp cultivars ‘Jin Ma’ and ‘NWG’ and three weed species i.e., A. tuberculatus, Glycine max L., and Setaria faberi L. to see how they affect each other through both intra- and interspecific competition. The outcome demonstrated that the weed species were responsible for the loss of yield as well as suppressing the growth of hemp. However, there were some mixtures where the plants were overyielding as well as the effects of two different hemp cultivars varied in response to the three weed species. Moreover, the effect of the three weed species was different based on hemp cultivars and mixture. These two studies suggest that controlling the weedy species in hemp fields is important to reduce the loss of hemp yield. Additionally, another separate greenhouse study looked at the accumulation of Trigonelline (TRG) in the leaves of two hemp cultivars ‘Jin Ma’ and ‘NWG’. The finding of this experiment demonstrates that the amount of TRG varies between when the plants grow under control and drought stress treatment. However, the two cultivars did not vary in terms of TRG accumulation. The three experimental studies showed that weeds have a significant effect on hemp growth parameters, and the accumulation of trigonelline varies based on drought conditions.

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Call number: LD2668 .T4 1978 K57 / Master of Science