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Determining The Factors That Drive Understory Plant Species Distribution In The White Mountains Of New Hampshire, Nathan Roe

Master's Theses and Capstones

Species niche is a fundamental concept in ecology, but quantitative descriptions of nicheare lacking for most species. We used new statistical techniques from species distribution modeling (SDM) literature to create estimates of niche for 41 understory species in the White Mountains of New Hampshire. Niche estimates allow for improved understanding of the environmental gradients determining the spatial patterns of species. We found that elevation and soil fertility were the dominant gradients influencing the distribution of our study species. The use of remotely sensed variables alone were capable of producing useful SDMs but were improved by the addition of soil variables. …

Determining The Factors That Drive Understory Plant Species Distribution In The White Mountains Of New Hampshire, Nathan Roe

Master's Theses and Capstones

Species niche is a fundamental concept in ecology, but quantitative descriptions of nicheare lacking for most species. We used new statistical techniques from species distribution modeling (SDM) literature to create estimates of niche for 41 understory species in the White Mountains of New Hampshire. Niche estimates allow for improved understanding of the environmental gradients determining the spatial patterns of species. We found that elevation and soil fertility were the dominant gradients influencing the distribution of our study species. The use of remotely sensed variables alone were capable of producing useful SDMs but were improved by the addition of soil variables. …

Goodbye And Thanks For All The Fish: The Inevitable Mass Extinction Of Vertebrate Wildlife In The United States By 2100 Ad, Richard Maximus Strahan

Master's Theses and Capstones

The last stages of a global mass extinction event (GME) that started in the Pleistocene is likely to be continuing across the nations of the Earth. In the United States (“Nation”), it will likely climax (“Climax”) by 2100 AD when it will wipe out about 80% of endemic, vertebrate wildlife species. It will reduce the populations and ranges of the Nation’s surviving vertebrate species to minimal values. This will be the 6th such mass extinction of wildlife species to have occurred in the Earth’s history.

This is a reasonable inference from available data reported in journal articles since 1990 on …

The Development, Validation, And Application Of The Eelgrass Health Index, Nicholas Anderson

Master's Theses and Capstones

Eelgrass (Zostera marina L) provides essential habitat and forage for waterbirds, fish, and other coastal marine species, nutrient and sediment capture which improves water quality, carbon storage, and wave energy buffering which reduces coastal erosion. Changes in its health can indicate other coastal ecosystem changes. Since the 1980s, eelgrass beds have declined in James Bay, Québec. The eelgrass decline coincided with a decrease in the abundance of migratory Brant and Canada geese visiting the coastal eelgrass meadows, which the geese rely on for forage during their spring and fall migrations. Geese are important species to the coastal First Nation Cree …

Developing Spectral Metrics As Early Indicators Of Water Stress Detection At The Canopy Level, Korik Vargas

Master's Theses and Capstones

Drought has become an increasing concern over the last few years in forest ecosystems. Understanding how forests respond to drought is critical to elucidate possible drought consequences for forest ecosystem structure and function. There is growing consensus that future climates will be characterized by extreme droughts and extreme precipitation events that will fall outside the historical range to which species and ecosystems are adapted. The limited information of how Northeastern U.S. forest tree species will respond to moderate to extreme drought events have promoted an increasing need to develop monitoring techniques which help us better understand the implications of future …

The Tallgrass Prairie Soundscape; Employing An Ecoacoustic Approach To Understand Grassland Response To Prescribed Burns And The Spatial And Temporal Patterns Of Nechrophilous Invertebrate Communities, Sarah Dodgin

Master's Theses and Capstones

Tallgrass prairies are rapidly vanishing biodiversity hotspots for native and endemic species, yet little is known regarding how spatial and temporal variation of prairie soundscapes relates to seasonal changes, disturbance patterns and biological communities. Ecoacoustics, the study of environmental sounds using passive acoustics as a non-invasive tool for investigating ecological complexity, allows for long-term data to be captured without disrupting biological communities. Two studies were carried out by employing ecoacoustic methodology to study grassland carrion food webs and to capture the phenology of a grassland soundscape following a prescribed burn. Both studies were conducted at the Nature Conservancy’s Tallgrass Prairie …

The Bioeconomics Of Shade-Grown Coffee Production Under Climate And Price Risks In Puerto Rico, Yixuan Gao

Master's Theses and Capstones

Coffee production is severely affected by global climate change. One of the important impacts comes from the increasing infestation and distribution of coffee berry borer (CBB), the most damaging coffee pest worldwide. Shade-grown coffee (SGC) systems can alleviate the impacts and increase the resilience of coffee farms by providing non-market and market ecosystem services.

From an ecological perspective, SGC systems can provide many non-market ecosystem services such as pest risk mitigation, soil water retention, soil fertility, and pollination, which are all critical factors affecting coffee yields. From a financial perspective, SGC systems can benefit farmers by increasing the prices through …

Home Range And Microhabitat Associations Of The Southern Red-Backed Vole (Myodes Gapperi) In New Hampshire Forests, Honora Tisell

Master's Theses and Capstones

Resources, such as food and shelter, are unevenly distributed across the landscape at both macro and micro scales. Home range is one measure of space use that reflects an individual’s resource requirements (e.g., microhabitat characteristics) and competition for those resources (e.g., density dependence). This study focuses on the home range of the southern red-backed vole (Myodes gapperi), comparing field methods for estimating home range and modeling the microhabitat characteristics that define the core area of the home range. Southern red-backed voles (Myodes gapperi) are common to boreal forests, most often found in coniferous or mixed deciduous stands, and in the …

Impacts And Management Of Foliar Pathogens Of Eastern White Pine (Pinus Strobus) In The Northeastern United States, Cameron Ducayet Mcintire

Doctoral Dissertations

White Pine Needle Damage (WPND) is a complex of foliar fungal pathogens currently impacting forests in the Northeastern US. Since ca. 2009, chlorosis and defoliation caused by WPND has been observed in stands of eastern white pine (Pinus strobus L) throughout the region. A changing climate, notably warmer temperatures and higher than average spring precipitation in the region are thought to be exacerbating the establishment and spread of these native pathogens. The goals of this research are to enhance the understanding of the timing and magnitude of WPND-induced defoliations across infected stands, assess the physiological response of trees affected by …

Wild Bee Declines And Changes In Plant-Pollinator Networks Over 125 Years Revealed Through Museum Collections, Minna Mathiasson

Master's Theses and Capstones

Though recent literature highlights widespread bee declines, detailed information on local communities, plant-pollinator network interactions and individual species remains distressingly scarce. In order to accurately direct conservation initiatives and to evaluate the status of wild bees and their host plants, long-term data on these populations is critical. Examining pollinator communities across regional scales highlights small-scale changes that go undetected in larger investigations. In light of unknown effects of introduced species and cumulative range expansions of exotic taxa, monitoring wild communities closely and extensively over time is becoming increasingly important. The focus of this thesis is to investigate a regional wild …

The Effects Of Invasive Tunicates On The Growth And Reproduction Of The Blood Star, Henricia Sanguinolenta, Kaitlin Samantha Van Volkom

Master's Theses and Capstones

Introduced species have become established in multiple systems around the globe where they are both predators and have been recognized as prey by native species. In the Gulf of Maine, introduced tunicates (Botrylloides violaceus, Diplosoma listeranium, and Didemnum vexillum) have become established in fouling and natural rocky benthic systems. In recent years, many native species such as Mitrella lunata and Stronglyocentrotus droebachiensis have recognized and begun to consume these introduced species. One such species is the native blood star, Henricia sanguinolenta. H. sanguinolenta, is a generalist sponge predator, but it has started to consume these invasive tunicate species as a …

The Photosynthesis-Foliar Nitrogen Relationship In Deciduous And Evergreen Forests In New Hampshire, Conor Madison

Master's Theses and Capstones

Biomass production in forests is a key process in the global carbon (C) cycle that is strongly linked to photosynthesis and related leaf traits. Spatially, relationships among leaf traits can vary as a function of climate, soils and species composition. As modeling approaches to estimate C gain improve, the need to understand variability in leaf traits becomes increasingly important. Here, we characterized the relationship between photosynthetic capacity (Amax), foliar nitrogen and leaf mass per area (LMA) within and across species in northern hardwood and evergreen stands of the White Mountain National Forest in New Hampshire, a region that has been …

Microbial Community And Vibrio Parahaemolyticus Population Dynamics In Relayed Oysters, Michael Anthony Taylor

Doctoral Dissertations

The CDC estimates that 45,000 people are sickened each year by foodborne Vibrio parahaemolyticus in the United States. Filter-feeding bivalve shellfish, such as oysters, are routinely inhabited by human pathogenic V. parahaemolyticus and there currently is not a contaminant management process that effectively reduces concentrations of V. parahaemolyticus in oysters. The transplanting of V. parahaemolyticus -laden oysters to an area with low concentrations or no V. parahaemolyticus, called oyster relay, is one reduction strategy that holds promise for treating live oysters. A key consideration for effective strategies to reduce Vibrio spp. in shellfish is the influence of microbiota in natural …

Effects Of Agricultural Practices On Soil Communities And Their Associated Ecosystem Services, Lesley W. Atwood

Doctoral Dissertations

To maximize crop yields, commodity crop production systems typically rely on inputs of fertilizers, pesticides, and irrigation; simplification of crop rotations (e.g., monocultures); and strategic use of soil disturbance (e.g., tillage, cultivation, etc.). While these practices are intended to optimize the soil conditions for crop development and reduce spatial and temporal variability in crop yield, they also impact soil biological diversity and the important agroecosystem services soil communities provide. Identification of management practices that are less prone to causing undesirable changes in the soil food web community are central to improving the sustainability of our agricultural systems. In this dissertation, …

Patterns And Drivers Of Carbon Fluxes In Temperate Forests, Andrew Ouimette

Doctoral Dissertations

Despite decades of carbon cycling research in terrestrial ecosystems, a complex suite of biotic and abiotic interactions make a complete understanding of the natural carbon cycle elusive. This thesis aims to advance our understanding of the carbon cycle, and stems from several ongoing projects aimed at quantifying carbon dynamics in forest ecosystems across a range of scales, with a specific effort to include both above and belowground components of forest ecosystems. I begin with a project using detailed chemical measurements on specific segments of root systems from two different tree species, in order to help refine methods that quantify the …

Nitrogen Dynamics And Retention In The River Network Of A Tropical Forest, Luquillo Mountains, Puerto Rico, Richard Brereton

Doctoral Dissertations

This dissertation identifies gaps in the scientific understanding of nutrient cycling, particularly nitrogen (N) cycling, in streams and riparian zones of tropical montane forests, and addresses several of those gaps with original field-based research using study watersheds in the Luquillo Mountains of Puerto Rico as the model system. The Luquillo Mountains have features typical of mature montane tropical forests, such as high background N concentrations in streams and groundwater relative to streams in other biomes. As a USDA Forest Service Experimental Forest, the Luquillo Mountains are accessible to researchers and have abundant monitoring and experimental datasets from which to build …

Phylogenetic And Phylogeographic Analyses Reveal A Species Complex In The Estuarine Nudibranch Tenellia Adspersa, Amanda Sobel

Master's Theses and Capstones

Until recently, the nudibranch genus Tenellia (Nudibranchia: Fionidae) was thought to include a single or group of species restricted to temperate estuarine waters. Given the addition of numerous other species from recent studies, the genus now encompasses species from polar, temperate, and tropical oceans from oceanic to estuarine salinities. One such fionid, Tenellia adspersa, is found in temperate estuarine waters globally and its presence is ecologically important as its congeners are capable of decimating colonies of their hydroid prey within a single generation (approx. 20-60 days). The literature is historically vague and conflicted on the morphology, taxonomy, and geographic distribution …

Moose Density, Habitat, And Winter Tick Epizootics In A Changing Climate, Kyle Ball

Master's Theses and Capstones

Unregulated hunting and habitat loss led to a near extirpation of moose (Alces alces) in New Hampshire in the 1800s. After state protection in 1901, the estimated population increased slowly to ~500 moose in 1977, then increased rapidly in the next 2 decades to ~7500 following an increase in browse habitat created by spruce budworm (Choristoneura fumiferana) and related timber salvage operations, and then halved from 1998-2016 despite highly available optimal habitat. The declining population was partially related to the specific management objective to reduce moose-vehicle collisions, and a possible change in deer hunter and moose behavior that influence population …

Land Use Change In The Northeast United States: Retaining Forest Structure And Its Soil Hydraulic Properties Through Silvopasture, Anthony John Stewart

Master's Theses and Capstones

Growing demand for locally produced agriculture in the Northeast US could result in significant land use change from forests to open pasture and other agricultural uses. This conversion may reduce the soil hydrologic flow due to tree removal and increased soil compaction, leading to increasing surface runoff and erosion. Silvopasture—an agroforestry system that integrates trees with livestock—offers a potentially more sustainable alternative to conversion to open pasture, and has recently gained interest with local land owners and farmers in the region. The retention of trees within pastures may help maintain critical hydrologic functions of forest soils by promoting higher infiltration …

Manganese Limitation As A Mechanism For Reduced Decomposition In Soils Under Long-Term Atmospheric Nitrogen Deposition, Emily D. Whalen

Master's Theses and Capstones

Long-term atmospheric nitrogen (N) deposition has been shown to reduce leaf litter and lignin decomposition in forest soils, leading to an accumulation of soil carbon. Reduced decomposition has been accompanied by altered structure and function of fungal communities, the primary decomposers in forest ecosystems; however, a mechanistic understanding of fungal responses to chronic N enrichment is lacking. A reduction in soil and litter manganese (Mn) concentrations under N enrichment (i.e., Mn limitation) may explain these observations, because Mn is a cofactor and regulator of lignin-decay enzymes produced by fungi. We conducted a 6-month incubation study to evaluate the effect of …

Discerning Differences Between Zooplankton Communities Based On Lake Trophic Status, Jonathan Dufresne

Master's Theses and Capstones

In 2007 the United States Environmental Protect Agency sampled 1157 lakes to determine the state of the nation’s lakes. The data they collected provided a unique opportunity to study the effects of eutrophication on zooplankton community structure across a range of lakes from a large geographical area. Using this data set two main questions were assessed: 1) what level of taxonomic identification is necessary to detect differences in zooplankton community composition as it relates to patterns in water quality and 2) in a dataset that has extensive spatial and temporal variability, how does one account for regional differences in zooplankton …

Channeled Whelk (Busycotypus Canaliculatus) Ecology In Relation To The Fishery In Vineyard And Nantucket Sounds, Massachusetts, Shelley Ann Edmundson

Doctoral Dissertations

Channeled whelks (Busycotypus canaliculatus) are predatory marine gastropods that support lucrative commercial fisheries along the east coast of the United States, with areas around Massachusetts supplying the largest landings. In the absence of a more thorough and comprehensive understanding of channeled whelk biology, it is unclear how to sustainably manage their fisheries. Within this dissertation, various aspects of whelk ecology were investigated to determine how to protect this species, while effectively managing the local fishery.

Early life history experiments revealed channeled whelk egg strings may incubate for 8 to 9 months in MA water temperatures. Incubation period decreased with increasing …

Limiting Impacts Of Invasive Glossy Buckthorn In Southeastern New Hampshire Woodlands: Studies Of Intensive Control And Forest Dynamics, Nicholas Lanzer

Master's Theses and Capstones

Invasive glossy buckthorn (Frangula alnus P. Mill) threatens forest communities in southeastern New Hampshire both ecologically and economically by outcompeting native regeneration and hampering forest management. Seventy-five white pine (Pinus strobus L.) seedlings surrounded mainly by buckthorn were identified at the MacDonald Lot property in Durham, NH. In spring 2015, fifty of these pines were encouraged to emerge from and overtop surrounding buckthorn by cutting all neighboring plants within 1 m; targeted herbicide was applied to cut stumps at 25 of these. Pine response was assessed after one growing season. Released pines showed increased diameter growth, foliar biomass, and stem …

Effects Of Salinity On Juvenile Cyclopterus Lumpus (Lumpfish) And Their Temproal And Spatial Distribution In The Great Bay Estuary, New Hampshire, Jenna Leigh Rackovan

Master's Theses and Capstones

Lumpfish (Cyclopterus lumpus) is a semi-pelagic species that is broadly distributed in the temperate portions of the North Atlantic. The lumpfish is also a commercially important species in Iceland and the Netherlands, where it is fished for roe that is used for caviar. Moreover, several recent studies have shown that lumpfish juveniles are useful ‘cleaner fish’ in the Atlantic salmon aquaculture industry. Despite the importance of the species, little is known about its physiology and ecology. The overall goal of this research was to investigate if, and how, salinity affects the physiology and ecology of juvenile lumpfish.

To determine the …

A Comparison Of Macrofaunal And Algal Communities In Oyster Aquaculture Gear, An Eelgrass Bed, Oyster Reef, And A Mudflat In Great Bay, New Hampshire, Megan Elizabeth Glenn

Master's Theses and Capstones

Oysters (Crassostrea virginica) and eelgrass (Zostera marina) are important ecosystem engineers in Great Bay, NH, however despite restoration efforts they have been in decline. In addition to loss of the resource, this degradation results in loss of associated ecosystem services such as habitat provision. It is possible that the recent increase in oyster farming in Great Bay could help mitigate habitat loss. My research objective was to quantify the biotic communities present in three natural habitats (eelgrass beds, oyster reefs and mudflats) in Great Bay NH and compare those to communities living on the type of gear (“racks and bags”) …

Effects Of Substrate Material On Marine Fouling Community Composition And Ascidian Larval Settlement, Anna Lindsey Chase

Master's Theses and Capstones

Driven by the rising global population and shoreline development, man-made marine structures are becoming ubiquitous in coastal areas. These alterations may have enormous ecological consequences, as anthropogenic structures provide novel habitat for marine organisms and often host communities that differ from those on natural substrates. These community differences are frequently driven by non-native species, which can be more prevalent on man-made marine structures than on adjacent natural surfaces. Although multiple factors, including light intensity, surface orientation, predation exposure, and habitat type, are known to contribute to these patterns, relatively few studies have directly examined the influence of substrate material on …

Invasive Plant (Alliaria Petiolata; Garlic Mustard) Homogenizes Fungal Communtiy Composition And Increases Fungal Richness, Mark Anthony

Master's Theses and Capstones

Non-native invasive plants can disrupt native plant communities and soil function (e.g., C and N cycling), but few studies have examined how soil microbial community structure differs in association with invasion. This work focused on Alliaria petiolata (garlic mustard), a non-mycorrhizal Brassicaceae that can displace native plants and reduce aboveground diversity. Garlic mustard produces toxic phytochemicals that can suppress mycorrhizal fungi, but we currently do not know if garlic mustard invasion affects the general fungal community, including specific mycorrhizal fungi, saprotrophic fungi, and plant pathogens and parasites. The objective of this work was to compare uninvaded and invaded soils from …

Hybrid Zone Dynamics Between Saltmarsh (Ammodramus Caudacutus) And Nelson's (Ammodramus Nelsoni) Sparrows, Jennifer Walsh

Doctoral Dissertations

Hybrid zones in nature have long been equated to “windows on the evolutionary process” providing unique environments to understand patterns of gene flow and introgression and the role of these mechanisms in maintaining biodiversity. Ongoing hybridization and introgression can lead to a number of conservation and evolutionary outcomes; as such, identifying the role of introgression in natural populations can provide new insights into species interactions while contributing to our understanding of evolutionary theory.

The research presented below characterizes hybrid zone dynamics between two tidal marsh endemics – the Saltmarsh (Ammodramus caudacutus) and Nelson’s (Ammodramus nelsoni) sparrow. Both species co-inhabit salt …

Space Use And Habitat Affinities Of The Singing Vole On The Northern Foothills Of The Brooks Range, Alaska, Andrew Maguire

Master's Theses and Capstones

Arctic tundra is being affected by a rapidly warming climate, which is accompanied by shifts in plant community composition and structure. Shrub expansion, a predominant consequence of this warming, is linked with changes in nutrient cycling and has direct implications to global change biology. Habitats are being altered across the landscape, with subsequent changes to arctic faunal communities. While herbivory has been noted as important in contributing to plant community composition in the arctic, with the potential to both exacerbate and mitigate shifts toward shrub-dominated tundra landscapes, little research has been conducted on herbivore dynamics. Microtine rodents (i.e., voles and …

Physiological Changes In White-Rot Fungi In Response To Simulated Nitrogen Deposition Are Not Readily Reversed Through Experimental Evolution, Elizabeth Amy Landis

Master's Theses and Capstones

Increases in nitrogen (N) deposition have been shown to slow decomposition of organic material including lignin, particularly in forests with high lignin content. Since basidiomycete fungi are the primary decomposers of lignin, their response to increases in available N are of interest. The Chronic Nitrogen Amendment Study at the Harvard Forest Long-Term Ecological Research (CNAS HF-LTER) site is an experimental N gradient in Petersham, MA. Since 1988, three megaplots have received varying levels of NH4NO3: ambient-only deposition (control), 50 kg N ha-1 yr-1 (N50), or 150 kg N ha-1 yr-1 (N150). In order to examine how species of lignin-degrading basidiomycetes …