This study has significantly broadened and deepened the understanding of ecological aspects related to the spread and reproduction of Diplodia pinea as an endophyte, latent pathogen and causal agent of serious disease problems in plantations of Pinus spp. Analyses of genetic diversity in populations using microsatellite data has revealed very high levels of genetic diversity of populations of the pathogen at different spatial levels, ranging from within a single asymptomatic tree to within and between plantations over large geographic areas and in different countries where the fungus has been introduced. Analysis of the structure of the distribution of genotypes and the association of alleles within populations, suggest that sexual recombination is occurring in most environments in the Southern Hemisphere D. pinea populations. This indicates the presence of a cryptic sexual state in this fungus. The genetic diversity was structured and differentiated for regions separated by as little as 65 km to a country and continental scale. The diversity and likely sexual reproduction of D. pinea must complicate control strategies such as selection and breeding for resistance. It is thus essential to strengthen quarantine services aimed at minimizing the risk of introducing additional genotypes of D. pinea. In this regard, understanding the infection and spread between regions is essential. Results of this study demonstrate that this fungus infects seeds, but only at low levels, and is not transmitted vertically via seeds to seedlings. Diplodia pinea was also not isolated from seedlings in three commercial nurseries and open fields in South Africa. These results provide strong evidence that neither seeds nor seedlings are the primary sources of inoculum, but that the pathogen is mainly transmitted horizontally from mature trees and debris left in plantations. Finally extensive sampling conducted as part of this study led to the discovery of the sibling species, D. scrobiculata in South Africa and outside the Northern Hemisphere for the first time. / Thesis (PhD)--University of Pretoria, 2011. / Genetics / Unrestricted

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Economics, 1978 / Bibliography: leaves 240-243. / by José Marcio A. Guimaraés de Camargo. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Economics

As one of antebellum Tidewater's most prominent planters, Hill Carter and the world he and his slaves made at Shirley occupy an important place in Virginia history. Few scholars, however, have analyzed their roles adequately. Previous studies' overwhelming concentration on the architectural and material culture history of the plantation has left Carter's role as one of Virginia's preeminent agricultural reformers virtually unexplored. Assuming ownership of Shirley in 1816, Carter quickly established himself as a leading proponent of agricultural improvement, both embracing and building on the ideas of other reformers like John Taylor and Edmund Ruffin. He diversified his crops and changed their rotations, used new equipment and improved methods of cultivation, reclaimed poor or unproductive lands, and employed a variety of fertilizers and manures to resuscitate his soils. Significantly, Carter efforts to improve Shirley transformed not only the physical landscape of the plantation. The changes produced in the work and lives of his slaves also were considerable. This study, then, investigates the relationship between agricultural reform and slavery. Instead of looking at reform in terms of how slavery affected (or inhibited) it, this work argues that reform must also be understood in relation to how it affected slavery, for changes manifested in attempts to improve lands had important ramifications on slave work routines, which, in turn, affected slave life in important ways. / Master of Arts

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More than 20 million clonal loblolly pines have been planted throughout the southeastern United States. Fertilizer has been applied to more than 6.5 million hectares of plantations to alleviate deficiencies of nitrogen and phosphorus that limit growth. Because cloning loblolly pine in large numbers has only become possible in the last decade, it is unknown how clones may respond differently to fertilizer application. Growth, growth efficiency, and biomass partitioning responses to fertilizer application were investigated among 25 clones planted in the Virginia Piedmont. Closely related clones varied in their fertilizer stem volume responses, but not enough to be statistically significant (p = 0.11). Clones varied in growth efficiency and partitioning to individual tissues, but clone-by-fertilizer interactions were not observed. Clonal variability was observed in root morphology, and maximum rooting depth showed a significant clone-by-fertilizer interaction. Clones with rapid growth rates can be selected with a range of other desirable traits. Short-term (i.e. weeks) responses to fertilization are often inconsistent with long-term (i.e. years) responses, but are critical to understanding growth responses. We investigated carbon allocation in two full-sibling clones of loblolly pine under two levels of fertilizer application over four months in a greenhouse. Using monthly harvests of some trees and ecophysiological measurements throughout, we determined carbon allocation on a monthly scale. In response to fertilizer application, both clones reduced allocation belowground and increased allocation to foliage to some extent, increasing whole-canopy photosynthetic capacity. However, these changes in allocation were ephemeral. By the end of the experiment, root-shoot ratios were no longer significantly affected by fertilizer application. Clones had allocation patterns distinct from one another, with one allocating more belowground and the other allocating more to stem mass. While their overall growth responses to fertilizer application were similar, the physiological mechanisms that resulted in these responses were different between clones. Results of the two studies indicate that while fertilizer responses may not need to be included when testing clones for deployment, knowledge of the fertilizer responses of widely-deployed clones would offer forest managers opportunities to apply clone-specific precision-silvicultural systems to optimize growth rates and manage for a range of products. / Ph. D.

This study assessed five fertilizer treatments (control – no fertilizer, urea, urea treated with N-(n-butyl) thiophosphoric triamide (NBPT), coated urea + NBPT (CUF), polymer coated urea (PCU) ) during two application seasons (spring, summer) to: 1) compare fertilizer nitrogen (N) losses (see Chapter 2); 2) evaluate temporal N uptake patterns of loblolly pine (see Chapter 3); and 3) evaluate fertilizer N cycling and partitioning in a loblolly pine ecosystem (see Chapter 4). Chapter 2 results showed enhanced efficiency fertilizers (EEFs) significantly reduced ammonia (NH3) volatilization losses compared to urea. Mean NH3 volatilization after spring fertilization ranged from 4% to 26% for EEFs versus 26% to 40% for urea, and 8% to 23% for EEFs versus 29% to 49% for urea in summer. Chapter 3 results showed an increase in timing and development of foliage in fertilized compared to unfertilized plots. In addition, the cumulative N uptake by loblolly pines increased over the entire growing season from N originating from fertilizer and natural sources. Chapter 4 results showed greater fertilizer N recovery for EEFs in both spring and summer (80%, 70-80% respectively) compared to urea (60%, 50% respectively) with most fertilizer N recovered from mineral soil (20% to 50%) and loblolly pines (10% to 50%). Three primary conclusions come from this research: 1) EEFs reduce NH3 volatilization after N fertilization compared to urea regardless of application timing and weather conditions (see Chapter 2); 2) N uptake by loblolly pines increases over the entire growing season after N fertilization (see Chapter 3); more fertilizer N remains in the ecosystem with EEFs compared to urea with most fertilizer N remaining in the soil (see Chapter 4). From these findings, we hypothesize that the EEFs in this study: 1) reduce ammonia volatilization which 2) translates to an increase in fertilizer nitrogen remaining in the loblolly pine plantation system that 3) increases the amount of plant available nitrogen for an extended period into the stand rotation and 4) increases fertilizer nitrogen use efficiency (FNUE) for all enhanced efficiency fertilizers investigated in this study compared to the conventional form of fertilizer N used in forestry, urea. / Ph. D.

<p>Even in our contemporary moment, the word plantation evokes a distinctly Southern and rural image in which slavery is well hidden within an idyllic botanical scene. And yet, from the very beginning of industrialization in the United States, plantation agriculture and enslavement were thoroughly embedded in the circuits of Northern capital and urbanization. "Shackled in the Garden" begins from the premise that the plantation is not an archaic institution that withered away in the nineteenth century, but rather is an enduring site of production and reproduction in the U.S. and throughout the Global South. Historically, the plantation has played a central role in organizing racialized bodies, technologies and environments in the South. In the wake of widespread ecological and social disaster across global Southern geographies, I insist that it behooves us to take another view of the plantation.</p><p>"Shackled in the Garden" rethinks the plantation as an ecological space: a space of dynamic relations in which racialized bodies and technologies are aggregated and disaggregated by a powerfully tropical environment. In the midst of ongoing crises over the sustainability of the plantation complex in the mid-eighteenth century, the plantation metamorphosized from an idyllic geography of botanical bounty and pure soil to a "toxic paradise": a tainted space that enclosed usable bodies and usable lands to be put in the service of increasingly experimental purposes. This peculiar conjoining of racialized subjects and the environment transformed the plantation into a privileged site for investigations into natural history, which sought to catalog and organize the natural world. Understandings of natural history as an innocent and feminine pursuit based on non-intervention and simple observation of the environment hid rampant experimentation on all kinds of "specimen" on the plantation including botanical species, agricultural crops, livestock, and enslaved persons. </p><p>While emergent biological models in the mid-nineteenth century began to understand race and identity as being rooted in the body, climatic or environmental determinations of identity continued to hold rhetorical power. Biology may have achieved a hegemonic position with the increasingly legitimated theories of Darwinian evolution, but natural history did not wither into oblivion. While individuation, mechanization, and biology flourished in the North, the plantation South continued to be figured as a natural ecology, a geography where identity refused its disentanglement from a dangerously miasmic and tropical environment. This project emerges out of both literary studies and science studies. Moving from James Grainger and Thomas Jefferson through Thomas Wentworth Higginson to Booker T. Washington, I explore how a literary imaginary of the plantation pastoral, which continued to represent the plantation as an unenclosed, pre-industrial and green geography in the face of extensive industrialization and environmental degradation, contributed to an understanding of the plantation as a "natural" space of scientific experimentation. The second half of the project considers a perhaps surprising genealogy of plantation fiction from authors such as Martin Delany and Jean Toomer who defamiliarized pastoral naturalizations of plantation space at the same time as they played on the heterotopic spatiality of the plantation to imagine a different, more global plantation South.</p> / Dissertation

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