Thesis (Ph. D.)--Oklahoma State University, 2006. / Vita. Includes bibliographical references.

Thesis (M. S.)--Oklahoma State University, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Oklahoma State University, 2006. / Vita. Includes bibliographical references.

Thesis (M. S.)--Oklahoma State University, 2006. / Vita. Includes bibliographical references.

Thesis (M. S.)--Oklahoma State University, 2006. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oklahoma State University, 2009. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oklahoma State University, 2009. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oklahoma State University, 2009. / Vita. Includes bibliographical references.

<p> In this dissertation, I asked how soil biota, abiotic stress, and plant provenance influence plant communities and interactions between plants. Soil biota can have positive or negative effects on individual plants, and also influence the diversity and productivity of plant communities through their net effects on individuals and by mediating plant-plant interactions. However, the level of abiotic stress experienced by plants is likely to drive plant responses to soil mutualists and antagonists. Additionally, plant provenance (e.g. population origin) can influence responses to abiotic soil conditions as well as to soil organisms. Understanding how these three interacting components shape plant interactions may improve success of restoration and invasive plant management. During restoration, the goal is typically to create conditions conducive to native plant reestablishment. However, amelioration of disturbed areas by reducing abiotic stress or by adding beneficial soil organisms may unintentionally increase colonization and growth of non-native plants. Using the applied context of mine restoration, I examined how soil biota, abiotic stress, and plant provenance affected plant communities and interactions in four studies. </p><p> In Chapter 1, I found that both a native grass (<i>Bouteloua gracilis </i>) and an invasive grass (<i>Bromus tectorum</i>) responded positively to soil biota when grown alone in the greenhouse. However, when grown together, the presence of soil biota increased the competitive ability of <i>Bromus,</i> while the removal of soil biota increased competition by <i>Bouteloua.</i> Results supported the hypothesis that invasive species such as <i>Bromus</i> often have positive responses to soil biota in the invaded range, but I also found that <i>Bromus</i> response to soil biota removal varied considerably by site. </p><p> In Chapters 2 and 3, I examined how methods used during restoration (application of stockpiled soil and inoculation with soil biota) affected native and non-native plant growth in field plots. I found that native plant biomass and non-native plant biomass both tended to increase when soil abiotic stress was ameliorated through the addition of deeper stockpiled soil. In addition, both native and non-native grasses responded positively to the use of local soil an as inoculant, while non-native forbs responded negatively to local soil inoculum. However, native plants only received significant benefits from inoculation when targeted application to native seedling transplants was used. Commercial mycorrhizal fungal inoculum did not affect plant growth. In studies of both stockpiled soil addition and soil inoculation, year was an important factor in determining plant responses. Variation in effects by year may reflect differences in precipitation timing or amount, or changes associated with plant and soil biota growth over time. </p><p> In Chapter 4, I used a greenhouse experiment to examine how one type of soil biota, arbuscular mycorrhizal fungi (AMF), influenced plant-plant interactions. I also manipulated abiotic stress (soil phosphorus availability) and plant provenance (stress-tolerant ecotype versus competitive ecotype) to assess whether these factors influenced AMF-mediated interactions among plants. I found that allowing or denying AMF hyphal access between neighboring pots altered plant reproduction. Inflorescence production was substantially decreased when hyphal access was allowed between two stress-tolerant plants. In addition, when hyphal access was permitted from a stress-tolerant plant to a competitive plant, the competitive plant flowered slightly sooner, whereas allowing hyphal access between two stress-tolerant plants led to slightly slower flowering. These results did not appear to be driven by abiotic stress or plant nutrition. It is possible that AMF transmission of infochemicals may play a role in regulating plant phenology and reproduction; however, further research in this area is needed.</p>

<p>This aim of this dissertation is to investigate "pedogenesis" (soil formation and change over multi-millennial timescales with minimal human impact) and "anthropedogenesis" (centurial and decadal soil formation and change through the Holocene with increased human influence) in the highly weathered, upland soils of the Southern Piedmont physiographic region in the southeastern United States. I start by combining an analysis of the cosmogenic nuclide meteoric beryllium-10 (10Be) with a mass balance analysis of pedogenic 9Be loss to estimate how long the Southern Piedmont Ultisol have been residing at Earth's surface. This coupled analysis indicates that pedogenesis has been operating in these highly weathered Ultisols for much, if not all, of the Quaternary; considerably longer than previously thought. Next, I utilize traditional soil analyses alongside iron stable isotope measurements to investigate how one century of reforestation after agricultural land abandonment impacts the coupled carbon -iron cycle in these ancient subsoils. This project suggests that widespread patterns of anthropogenic land use change in the Southern Piedmont have caused significant subsoil changes that impact carbon storage and the distribution of iron deep below ground. Finally, I analyze over 50 years or repeated soil and forest ecosystem observations from the Calhoun Experimental Forest to investigate the relationship between soil macronutrient contents aboveground forest ecosystem development in the region. These long term observations suggest that decadal patterns of secondary forest growth and decline fundamentally alters the role that soils plays in individual ecosystem nutrient cycles and that the potential for ecosystem nutrient loss is highly nutrient dependent, despite well-established ecological theory.</p> / Dissertation