Soil organic carbon (SOC) is concentrated in coastal wetlands, and its permanence maintains a livable climate, yet dynamics that govern microbial activity and SOC persistence are not fully characterized in coastal wetlands. Though microbial activity is conventionally thought to facilitate SOC loss, soil microbes simultaneously direct SOC formation. In fact, microbially-processed materials constitute up to half of the terrestrial soil organic carbon pool. Environmental conditions can affect whether microbes yield a net gain or loss of SOC, yet there is little consensus on microbial drivers of soil carbon longevity in coastal ecosystems. I sought to identify which drivers of microbial activity have the greatest impact on SOC in salt marsh soils. To address this question, I conducted a meta-analysis using the PRISMA method. Based on an initial survey of 2,835 studies, numeric data on soil and ecosystem characteristics were collected across 50 studies on over 60 salt marshes located around the world. Integrative data analyses, including structural equation modeling (SEM), were applied to synthesized data to identify environmental drivers of SOC in salt marsh ecosystems. Across a wide range of study sites, analysis of over 20 variables shows that soil characteristics are tightly linked. Salinity, pH, nitrogen, and phosphorus are associated with increased microbial biomass and soil organic carbon. Correlations between microbial biomass carbon and SOC are strengthened by soil salinity and nitrogen, and they are weakened by moisture. Correlations were dependent on the means by which variables were measured, yet findings were consistent across study sites. These results suggest that soil carbon content is affected by drivers of microbial activity. Observational findings set the stage for experimental strategies that parcel causal effects of microbial activity on SOC from confounding effects of covariant environmental conditions. I identified that nitrogen, phosphorus, salinity, pH, and moisture influence microbial contributions to SOC. These environmental drivers, as well as microbial biomass and greenhouse gas flux, should be considered key indicators of soil health when assessing the sustainability of coastal SOC. Identification of environmental drivers of microbial function enables design of land management strategies that promote conditions conducive to coastal soil carbon longevity.

Acoustic telemetry is an important tool when studying the spatial ecology of marine animals. First, it is important to identify the challenges of using this tool in shallow tropical marine environments before tracking marine animals. One significant issue that can influence the effectiveness of acoustic telemetry is the efficiency or detectability of acoustic signals by receivers. Understanding factors influencing detection efficiency of acoustic tags is especially important for fine-scale positioning systems (such as the VEMCO positioning system, VPS) that use detections in an overlapping receiver network to calculate geographic positions of tagged fish. I modelled the efficiency of an acoustic array in a tropical reef flat in Culebra, Puerto Rico and then tested the capability of detecting and positioning tagged permit (Trachinotus falcatus) and great barracuda (Sphyraena barracuda). Detection efficiencies were analyzed for a fine-scale array comprised of 25 receivers and 17 sync tags deployed as a fine-scale array for nearly three years. I used a generalized linear mixed-effect model Template Builder Model (glmmTMB) that helped elucidate the environmental variables that play a role in influencing the ability to detect transmitter signals. Then, I evaluated how well the fine- scale array was at detecting tagged permit (n=1) and great barracuda (n=4) using the reef flat. Once, the model was created, it was used to predict the likeliness of hourly detections of sync tags and tagged animals. Finally, the fine-scale and broad-scale array consisting of 59 receivers were used to determine the spatial movement patterns of permit and great barracuda. A glmmTMB was created to determine what environmental variables were present when each species visited the fine-scale array in the coral reef flat. The dynamic Brownian-Bridge Movement Model (DBBMM) was used to determine the fishes’ home range within the coral reef flat using X Y locations. Network connectivity was used to determine each fishes’ spatial movement patterns and community structure related to the receivers they visited. Lastly, spatial patterns throughout each diel period and season were determined. Collectively, this study revealed the benefits and limitations of using fine-scale acoustic telemetry in shallow coral reef ecosystems.

Human occupation of the New England region of North America during the early Holocene has long been established archaeologically. However, the data exists almost solely from terrestrial sites. Vast portions of aerial land once available to early occupants of the area for resource procurement and living surfaces are now submerged. Underwater pre-Contact resources embedded in these submerged landforms will undeniably contribute to a holistic understanding of New England's cultural history. Examination of current archaeological procedures reveal that the archaeological standards, practices, and theories commonly employed in terrestrial archaeology are largely not being extended past the coastline into the underwater environment. This is due, in part, to the past history of professional skepticism regarding the preservation and accessibility of terrestrial archaeological deposits post-Holocene sea level rise. A report of global, submerged, terrestrial archaeology projects that show submerged, intact resources challenge this skepticism. A detailed review of an underwater survey in Boston Harbor, designed to predict, locate, and investigate submerged pre-Contact sites, is used as a case study to argue that these resources deserve the same rigorous study as terrestrial archaeological resources. Post-glacial deposition may act as an agent of preservation in New England waters, and past concerns of transgressive erosion are discussed in light of current geophysical research. Recommendations of how and why submerged pre-Contact archaeological resources should become commonplace within archaeological inquiry are supported by advances in technology, increased geophysical survey of the marine environment and knowledge of the prevailing laws governing archaeological resources underwater.

Abstract (Summary) Wood turtles ( Glyptemys insculpta ) are of conservation interest rangewide. Anecdotal accounts demonstrate that some populations have been decimated since 1850, and recent studies demonstrate that declines are still underway. From 2004-2008 I investigated the ecology of wood turtles in Massachusetts and New Hampshire. I obtained between one and five years of annual home range data for 150 turtles, and evaluated population structure at 31 sites in five major watersheds. Seasonal floods displaced 7% of wood turtles annually in one watershed, and accounted for elevated mortality. Twelve wood turtles were displaced < 16.8 km, and two were displaced over a 65-foot dam. Several turtles overwintered at their displacement site and two returned successfully, indicating that floods are a mechanism of population connectivity. Several homing turtles ended up in new areas. Turtles occupied stream segments with gradient < 1%, lower than generally available. Agricultural machinery accounted for most observed mortality, followed by automobiles and mammals. Female turtles exhibit smaller home ranges in agricultural areas. Older turtles move farther from the river than do young turtles, possibly reflecting their familiarity with a former landscape. Population density ranged from 0-40.4 turtles/river-kilometer. The highest densities occur in central New Hampshire and lower densities occur in the Housatonic watershed. Population density is negatively correlated with agriculture at both riparian and watershed scales, and responds unimodally to forest cover. Wood turtle populations in western Massachusetts are declining by 6.6-11.2% annually. I estimated ages of turtles by assessing shell-wear rates from photographs. Wood turtles regularly achieve ages over 80 years, and like related species, do not exhibit clear signs of senescence. Old wood turtles are reproductively dominant, and their survival rates are twice as high as young turtles. Carapace scutes appear to require 80 years to become worn. Population modeling indicates that wood turtle populations are declining in New England due to anthropogenic and natural factors. Conservation efforts must address the effects of agriculture on adult survival. Climate change may negatively affect northeastern wood turtles through increased flooding. Populations in mountainous areas may be likely candidates for conservation because they don't occupy prime agricultural land, but may be more susceptible to floods.

The riverbottom forest community of St. Mary River, Lee Creek and Belly River in southwest Alberta, Canada is a unique ecological entity characterized by poplar species having their major Alberta distribution along these streams. Stands in the community are dominated by three tree species, six shrub species and nine herb species. Establishment of the community is dependent on climate and substrate; destruction is the result of progressive lateral stream-flow erosion. Soils are sandy loams above gravel, with pH values of 7.7 to 8.0 and soluble salt concentration of 176 to 458 parts per million. Trees in mature stands averaged 23.0 centimeters in diameter and 40 years in age; maximum tree age was 250 years. The vascular flora consists of 294 species of which 44 are woody and 250 herbaceous. One species (Prunus nigra Ait.) new to Alberta and range extensions for 13 species are cited. There are no true community endemic species. Recreational and livestock raising uses are present community modifiers. Fire is not important in current forest dynamics.

Macroinvertebrate populations in the Weber River, Summit County, Utah, were analyzed to determine what effects channelization resulting from Interstate-80 construction and water impoundment had on the standing crop, species diversity and species composition. Bottom samples were collected monthly from riffle areas in channeled and unchanneled sections and above Echo and Wanship Reservoirs. Macroinvertebrate populations in the channeled areas were similar in standing crop, species diversity and species composition to those in unchanged areas within six months following channelization. Species diversities were higher (d=4.1, 3.7) above the reservoirs than below (d=2.0). The reservoirs restricted the distribution of several species of macroinvertebrates. The effects of channelization on the macroinvertebrate fauna in the Weber River were negligible, but water impoundment influenced the species composition and species diversities of the populations occurring in the tailwater.

Raptor nests on human-built structures represent a significant source of conflict as they can result in bird mortality, fires, structure damage, service distribution, or power outages when falling nest materials or animals connect with energized conductors. Power companies, such as the Tennessee Valley Authority (TVA), wish to mitigate these conflicts to avoid service disruptions. In this dissertation, I present my work towards understanding and mitigating the interactions between Ospreys (Pandion haliaetus) and human-made structures. To achieve this, I explored multiple elements of conflict identification, monitoring, and basic ecology of the target species to better inform conflict mitigation. In Chapter I, I modelled the influence of suitable habitat and transmission infrastructure distribution on the potential risk of nest-infrastructure conflict within the TVA power service area. My integrative model would be most useful to utilities when adjacent (i.e., within 10 km) areas to ‘risky’ zones are also considered when looking at mitigation efforts and pre-development planning. Going forward, similar models for other species and for distribution structures may benefit utilities such as TVA. In Chapter II, I aimed to identify the most suitable nest monitoring technique for Ospreys, as nest information is required to make informed decisions for conflict mitigation (e.g., nest removal). I found that unoccupied aircraft systems, or drones, are less disturbing and more time-efficient than other methods tested. In the last two chapters, I focused on obtaining detailed information on the basic ecology of Ospreys in the southeastern United States, which represent an understudied population. My findings in Chapter III contribute to general migration ecology theory, identify key stopover areas for Ospreys in Florida, provide valuable comparisons for further investigations, highlight areas for future research, and identify possible metrics relevant to conservation and management action. Lastly, I quantified the genetic diversity and structure of southeastern Ospreys to generate hypotheses for future testing and provide valuable comparisons for further investigations. While gene flow appears to be high and sampled regions show little genetic differentiation, more research is required to elucidate patterns of cryptic population structure and provide concrete implications for management decisions (e.g., source population for translocation programs).

<p>Although decades of experience in human spaceflight have produced and refined a wealth of operational knowledge, the unique challenges posed to long-term extraterrestrial surface habitats will require new approaches to mission design. The key objectives of this thesis are to develop an understanding of 1) how to use simulation to study these habitats and 2) how to make contingency plans for these habitats under complex, changing conditions. In order to accurately represent the challenges posed, we identify the common qualities of mission architectures that are likely to be present in near-future habitats. These qualities are used to formulate sample crew schedules that contribute to developing realistic models for meaningful research. We discuss the development of such models and demonstrate the suitability of simulation to enable the design and study of resilient space habitats. Simulation can be used as a tool to understand the challenges and consequences associated with decision making, as well as the importance of resilient design choices in a hazard-prone environment. We then identify aspects of vulnerability in space habitat mission operations, the subfactors that influence changes in habitat vulnerability, and the effects of each identified category of vulnerability. These ‘vulnerability factors’ are subsystem availability, environmental conditions, safety control options, and recent events. Each vulnerability factor has several subfactors that influence its change during a mission.</p> <p><br></p> <p>The set of vulnerability factors is significant because each captures some category of behavior in surface habitats that changes over time and impacts the likelihood or consequences of risks to the habitat. We use these vulnerability factors to formulate six research questions which can be addressed via simulation-based research. A simulation set plan is developed to highlight the significant concepts at play in each research question. Finally, we conduct trials and analyses of these questions via simulation by injecting faults into a modular coupled virtual testbed for space habitats. The results of the simulations are used to develop lists of key implications for each vulnerability factor in practice. In addition, the lessons learned over the course of simulation set design and the usage of the simulation tool are discussed to support future simulation-based research efforts. We conclude by summarizing the major findings and potential for future work in the area.</p>

During the last decade, the average mobile wireless data usage per person has tremendously increased. An even faster growth of the traffic demand is expected for the incoming years, due to several factors such as the increasing global population, the spread of the Internet of things (IoT), and the development of advanced technologies that require a higher amount of data. While mobile communication technologies have rapidly evolved to meet this need in the most usual situations, it is expected that the sixth generation (6G) of mobile connectivity will be the first one paying considerable attention to under-connected environments such as low-income, remote, or disaster-struck regions. Many specialized researchers and entrepreneurs are trying to design and implement alternative network architectures specifically meant for enhancing the performances of the current telecommunication (telecom) infrastructure. In particular, the use of aerial base stations (ABSs) has received considerable attention due to the main advantages of easy deployability and low-cost that are typical of unmanned aerial vehicles (UAVs), which are available in several fashions depending on the application; moreover, UAVs are also eligible to carry reflective intelligent surfaces (RISs), which represent a promising technology that allows to reflect signals towards specific directions. Another possibility that we have investigated consists in integrating the transceivers inside or atop existing rural wind turbine (WT) towers, in order to increase the coverage radius while avoiding the cost of building a separate telecom infrastructure. A powerful mathematical tool for evaluating the performance metrics of either terrestrial, aerial, or vertical heterogeneous wireless networks is stochastic geometry (SG), since it can be used to model the locations of the base stations (BSs) according to tractable spatial distributions (with either a fixed or a random cardinality) in order to imitate the typical deployments of the nodes made in realistic scenarios; in particular, in this work we focus on rural and post-disaster situations. SG makes use of point processes to model networks' topologies. The developed spatial models, in turn, allow us to analyze the quality of service (QoS) experienced by the typical user served by the proposed networks. To this extent, we creatively and efficiently studied our inhomogeneous systems by making use of what we call the indicator method, meaning that we do not subdivide the ground plane in multiple homogeneous sub-regions, but we use indicator functions to provide general expressions that are valid over the entire ground plane. To prove the effectiveness of the novel architectures, insightful comparisons with the conventional ones are presented.

Climate change is posing a significant threat to terrestrial ecosystems worldwide, in part due to the more frequent occurrence of extreme climatic events such as droughts. While the importance of drought impacts on vegetation has been widely recognized, the time-dependent characteristics of drought-induced response remain insufficiently understood. In this study, we examine the sensitivity of terrestrial evapotranspiration (ET) to water availability in African biomes using a suite of satellite and geospatial data. By correlating a multi-scalar drought index with monthly ET anomalies between 1981 and 2016, the spatiotemporal effects of drought are evaluated and compared against simulations from a coupled vegetation-climate model. The coupling between water availability and ET is found to be largely dependent on aridity conditions and the evapotranspiration regime (energy- vs. soil moisture-limited). We also observed the dominant role of root zone storage capacity in mediating ET response among rainforests and savannas, whereas shrubs and grasslands tend to exhibit much more complex soil-plant interactions. Comparing between model simulations and observations, discrepancies in the magnitude and timing of ET response were evident. Our findings highlight the need for an explicit consideration of plant-available water to improve the representation of hydroclimatic processes in Earth system models.