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Hydrothermal processes play a major role in transporting mass and energy in Earth’s crust. These processes rely on hydrothermal fluid, which is dissolving, transporting and precipitating minerals and distribute heat. The composition of the hydrothermal fluid is specific for various geological settings, but in most cases it can be approximated by H₂O-NaCl-CO₂ fluid composition. The flow of hydrothermal fluid is controlled by differences in temperature, pressure and/or density of the fluid and hydraulic conductivity of the rock. In my work, I was focused on modeling of the hydrothermal fluid properties and experimental characterization of fluid that formed emerald deposit in North Carolina, USA. The dissertation based on the result of three separate projects. The first project has been dedicated to characterization of the H₂O-NaCl hydrothermal fluid ability to transport mass and energy. This ability of the fluid is defined by a change in fluid density and enthalpy in response to changing pressure or temperature. In this project we quantified the derivatives of mass, enthalpy and SiO₂ solubility in wide range of pressure, temperature and composition (PTx) of H₂O-NaCl fluid. Our study indicated that the PT region in which fluid is most efficiently can transport mass and energy, located in the critical region near liquid-vapor phase boundary and the sensitivity to changing pressure-temperature conditions decrease with increasing salinity. In second project we developed the revised H₂O-NaCl viscosity model. Revised model to calculate the viscosity of H₂O-NaCl reproduces experimental data with ±10% precision in PTx range where experimental data available and follows expected trends outside of the range. This model is valid over the temperature range from the H₂O solidus (~0 °C) to ~1,000 °C, from ~0.1 MPa to ≤500 MPa, and for salinities from 0-100 wt.% NaCl. The third project has been focused on the characterization of formation conditions of the emerald at North American Emerald Mine, Hiddenite, North Carolina, USA. The emerald formation conditions defined as 120-220 MPa, 450-625 °C using stable isotope, Raman spectrometry, and fluid inclusion analysis. Hydrothermal fluid had a composition of CO2-H2O±CH4, which indicates mildly reducing environment of emerald growth. / Ph. D.

Invasive plants, animals, insects, and pathogens are a significant problem for land managers and conservationists as they can cause irreparable damage to local ecosystems. The emerald ash borer (EAB), an invasive beetle from China, was discovered in the U.S. in 2002, and has decimated ash populations throughout Michigan. It continues to move through Midwestern and some eastern states, usually killing a tree within 2-4 years of infection. Using a Global Positioning System (GPS) and Geographic Information System (GIS), all trees ≥ 45 cm and all ash ≥ 30 cm in diameter were measured and mapped within a 160 acre old-growth deciduous forest in northern Indiana. EAB was detected in 14 trees throughout the forest. A canopy map was generated, estimating 6.6 percent canopy loss due to EAB. Because of this research, the entire spread of EAB within this forest can now be documented and mapped. The methodological framework used in this research can assist land managers and property owners monitor their land by enabling them to: track changes in tree health more accurately; assess damage by creating forest inventory and canopy maps; and model potential damage over time. / Department of Natural Resources and Environmental Management

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<p>This study is part of an ongoing project established in 2007 as an emerald ash borer (<em>Agrilus planipennis</em>) trapping study. The primary objective of this thesis was to assess how forests have changed following the loss of ash over a 15-year period, from 2007 to 2022. The study aimed to answer three key questions: 1) How has the loss of ash affected the regeneration and recruitment patterns of ash and other tree species? 2) Which specific species are driving forest regeneration and recruitment in the absence of ash? 3) Can the data be used to predict future changes in forest composition following the loss of ash? To achieve these objectives, I conducted analyses of 44 forests representing 19 different forest types in Indiana, Michigan, and Ohio. Forest composition was examined at the overstory, midstory and understory levels to capture the overall impact of ash loss on forest regeneration and succession. Despite the decline or total loss in overstory ash, ash regeneration continued at most sites from 2017 to 2022. However, ash regeneration was not observed at 15 sites, and competition from established shade-tolerant species, such as red maple and American elm, was identified as a primary factor hindering ash recruitment. The loss of ash did not lead to significant changes in forest types. Forest types at all sites remained stable, with only minor shifts in dominant species. Tree species that were already present in the overstory filled the space left by the lost ash, thereby maintaining the existing forest types. In terms of driving species, my findings demonstrated a rapid increase in red maple dominance across all sites, particularly in the absence of ash. Red maple exhibited vigorous growth, suggesting it plays a crucial role in shaping future forest composition following ash loss. Other species, including black cherry, American elm, and American basswood, also contributed to forest regeneration, with some sites showing a shift toward a higher abundance of these species. Although the loss of ash has led to changes in forest composition, existing species have shown resilience and adaptability in filling the niche left by the lost genus. The long-term effects of emerald ash borer infestation on forest ecosystems are complex and multifaceted. This study provides insights into the regeneration and recruitment patterns of ash and other tree species following ash loss. The data suggest that while forests have experienced loss of ash, the remaining understory and midstory individuals of this species may contribute to future overstory recruitment. Furthermore, the dominance of red maple highlights its potential as a key driver of forest composition in the wake of ash loss. </p>

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In this dissertation, we study integrodifference equations in patchy landscapes. Specifically, we provide a framework for linking individual dispersal behavior with population-level dynamics in patchy landscapes by integrating recent advances in modeling dispersal into an integrodifference equation. First, we formulate a random-walk model in a patchy landscape with patch-dependent diffusion, settling, and mortality rates. We incorporate mechanisms for individual behavior at an interface which, in general, results in the probability-density function of the random walker being discontinuous at an interface. We show that the dispersal kernel can be characterized as the Green's function of a second-order differential operator and illustrate the kind of (discontinuous) dispersal kernels that arise from our approach. We examine the dependence of obtained kernels on model parameters. Secondly, we analyze integrodifference equations in patchy landscapes equipped with discontinuous kernels. We obtain explicit formulae for the critical-domain-size problem, as well as, explicit formulae for the analogous critical size of good patches on an infinite, periodic, patchy landscape. We examine the dependence of obtained formulae on individual behavior at an interface. Through numerical simulations, we observe that, if the population can persist on an infinite, periodic, patchy landscape, its spatial profile can evolve into a discontinuous traveling periodic wave. We derive a dispersion relation for the speed of the wave and illustrate how interface behavior affects invasion speeds. Lastly, we develop a strategic model for the spread of the emerald ash borer and its interaction with host trees. A thorough literature search provides point estimates and interval ranges for model parameters. Numerical simulations show that the spatial profile of an emerald ash borer invasion evolves into a pulse-like solution that moves with constant speed. We employ Latin hypercube sampling to obtain a plausible collection of parameter values and use a sensitivity analysis technique, partial rank correlation coefficients, to identify model parameters that have the greatest influence on obtained speeds. We illustrate the applicability of our framework by exploring the effectiveness of barrier zones on slowing the spread of the emerald ash borer invasion.