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Taking Nitrogen By Storm: Spatial And Temporal Controls On Nitrogen Processing In A Small Reservoir, Eliza Balch

Master's Theses and Capstones

Nitrate inputs pose a threat to aquatic ecosystems, leading to eutrophication, algal blooms, and habitat loss in downstream coastal marine and estuarine habitats. Rivers and streams can attenuate nitrogen between inputs and coastal outputs, moderating ecosystem harm. While nitrogen dynamics in streams and rivers have been studied for decades, less is known about the wetlands through which they flow, namely small reservoirs. Storms can have a large influence on nitrogen processing in reservoirs through hydrologic changes and introduction of new solute sources, but are poorly understood. To understand the spatial and temporal variability of nitrogen processing in a small reservoir, …

Taking Nitrogen By Storm: Spatial And Temporal Controls On Nitrogen Processing In A Small Reservoir, Eliza Balch

Master's Theses and Capstones

Nitrate inputs pose a threat to aquatic ecosystems, leading to eutrophication, algal blooms, and habitat loss in downstream coastal marine and estuarine habitats. Rivers and streams can attenuate nitrogen between inputs and coastal outputs, moderating ecosystem harm. While nitrogen dynamics in streams and rivers have been studied for decades, less is known about the wetlands through which they flow, namely small reservoirs. Storms can have a large influence on nitrogen processing in reservoirs through hydrologic changes and introduction of new solute sources, but are poorly understood. To understand the spatial and temporal variability of nitrogen processing in a small reservoir, …

Rates And Drivers Of Nitrate Uptake In Fluvial Wetlands In Urbanizing, Coastal Watersheds, Christopher Thomas Whitney

Master's Theses and Capstones

Humans have had a substantial impact on the global nitrogen cycle, releasing large amounts of reactive nitrogen to the landscape. Watersheds have been found to remove substantial quantities of this anthropogenic nitrogen, with aquatic networks preventing much of it from reaching the coast. Within these aquatic networks, channelized streams have been studied extensively. However, in many coastal watersheds, fluvial wetlands are a large component of the aquatic network yet have not been studied as broadly as channelized reaches. As fluvial wetlands are also likely to have a sizeable impact on river network-scale nitrogen removal, a greater understanding of their effect …

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 …

Remote Sensing Of Foliar Nitrogen In Cultivated Grasslands Of Human Dominated Landscapes, Paul Adam Pellissier

Master's Theses and Capstones

Foliar nitrogen (N) concentration of plant canopies plays a central role in a number of important ecosystem processes and continues to be an active subject in the field of remote sensing. Previous efforts to estimate foliar N at the landscape scale have primarily focused on intact forests and grasslands using aircraft imaging spectrometry and various techniques of statistical calibration and modeling. The present study was designed to extend this work by examining the potential to estimate the foliar N concentration of residential, agricultural and other cultivated grassland areas within a suburbanizing watershed. In conjunction with ground-based vegetation sampling, we developed …

Parameterization Of Transient Storage And Nutrient Retention In Coastal New England Wetlands, Sophie Wilderotter

Master's Theses and Capstones

Wetlands may play an important role in the removal of nutrients from river networks. In order to better understand this process, field observations for eight wetland-dominated reaches in coastal Massachusetts and New Hampshire were parameterized for transient storage and nutrient uptake rate constants. Transient storage was observed in all study wetlands, but the amount of storage and how connected the storage areas were to the wetland channel were not easily related to wetland physical characteristics: including wetland length, wetland width, wetland area, sinuosity, and length-to-width ratios, depth of the off-channel area, width of the off-channel area, cross-sectional area of the …

Modeling Long-Term Carbon Accumulation Of Tropical Peat Swamp Forest Ecosystems, Sofyan Kurnianto

Master's Theses and Capstones

Peatlands play an important role in the global climate system and carbon cycle; their large carbon stocks could be released to the atmosphere due to climate change or disturbance, resulting in increased climate forcing. I modified the Holocene Peat Model (HPM), a process-based model coupling water and carbon balance for simulating carbon dynamic over millennia, to be applicable for tropical peatlands.

HPMTrop outputs are generally consistent with the field observations from Indonesia. The simulated long-term carbon accumulation rate for coastal and inland peatlands were 0.63 and 0.26 Mg C ha-1 y -1, and the resulting peat carbon stocks at the …

Throughfall Chemistry In Deciduous And Coniferous Forest Stands At Thompson Farm, New Hampshire, Musa Dinc

Master's Theses and Capstones

In this study, I compare the chemical composition of throughfall in deciduous and coniferous forest stands to the chemistry of wet deposition. The study was conducted at Thompson Farm, Durham NH, which is owned and managed by the University of New Hampshire. Thompson Farm (43.11N, 70.95W) is at an altitude of 23 m and about 24 km from the Gulf of Maine. Throughfall samples were obtained from two forest stands using wet-dry Aerochem Metrics 301 collectors and rainfall samples were collected in a wet-only precipitation collector (N-CON Atmospheric Deposition Samples Model 00-120) from 14 April 2009 to 14 November 2009.The …

Ecosystem Structure And Function In An Urban, Piped Stream, Amanda Hope

Master's Theses and Capstones

Piped streams, or streams that run underground, are common features in urban areas. However, there is little empirical evidence regarding their ecological structure and function. This study measured ecosystem metabolism, nutrient uptake, and related characteristics of Pettee Brook -- an urban stream that flows through several pipes under impervious surfaces near the UNH (Durham) campus.

Piped and open reaches of Pettee Brook had similar water quality, nutrient uptake, and ER. However, the absence of light in piped reaches led to their complete loss of GPP. Benthic AFDM and chlorophyll a biomass were also significantly reduced in piped reaches. For both …

Dissolved Organic Carbon Quantity And Quality In North American Rivers And Streams, Kevin Walker Hanley

Master's Theses and Capstones

The controls on the quantity and chemical composition of dissolved organic carbon (DOC) in freshwater systems are crucial to understanding and managing processes like carbon sequestration, heavy-metal transport, and municipal water sanitization. We analyzed DOC quantity and quality for 17 major North American rivers and the temporal variability of DOC quantity and quality in several thousand small basins. Among large basins, we found positive correlation between wetland-cover and both DOC concentration (R²=0.78; p<0.0001) and specific ultraviolet absorbance at 254nm (SUVA254; R²=0.91; p<0.0001). We found that the role of river networks in altering the annual DOC signal minimal except in systems with long residence times. Among small basins, we found characteristics like runoff, stormflow, and vegetation indices useful in predicting the temporal variability of DOC concentration. Further work should clarify where individual characteristics drive DOC variability and more rigorously define the role of processing in large rivers.

Investigation Of Chromophoric Dissolved Organic Matter As A Freshwater Tracer In The Kennebec River Estuary, Alison Barner

Master's Theses and Capstones

In an attempt to explore the feasibility of using chromophoric dissolved organic matter (CDOM) as a freshwater tracer in the Kennebec Estuary of Maine, potential causes of the variability of the CDOM absorption coefficient (ag412) in relation to salinity were investigated. A predictable relationship between CDOM variability and factors such as river discharge and season was sought to explain CDOM variability for use in remote sensing. To accomplish these objectives, ag412 was calibrated to continuous underway FDOM measurements using linear regressions from 14 cruises. USGS daily discharge rates were checked for possible relationships with ag412 values. Although no trends were …

Hydrogen Dynamics In Soil In Northern Boreal And Subarctic Sweden, Kaitlyn J. Steele

Master's Theses and Capstones

Molecular hydrogen (H2) is produced and consumed through syntrophic organic matter decomposition in soil. The purpose of this study was to determine if organic-rich soils can become a temporary source of H2 to the atmosphere under anoxic conditions and the release of labile carbon.

H2 was generally consumed at the subarctic peatland, but the net H2 uptake decreased as site moisture increased from the dry palsa site to the wet Eriophorum site. The dissolved H 2 concentrations suggest that methanogenesis is the predominant decomposition pathway at depth and other decomposition processes or plant-mediated transport influence concentrations closer to the surface. …

Controls On Variability Of Dissolved Greenhouse Gas Concentration And Emissions From Small Streams In Southeastern New Hampshire, Jason Baillio

Master's Theses and Capstones

Small streams often present the first opportunity for dissolved greenhouse gases to exchange with the atmosphere and can be potential hot spots for evasion. In this study three streams in southeastern New Hampshire representing differing landuse were monitored for emissions of nitrous oxide, methane, and carbon dioxide. Average emission rates of N2O varied from -84 mug N m-2 day-1 to 2,561 mug N m-2 day-1 and correlated strongly with NO 3- concentration. One stream, Rum Brook, was found to be a net sink for N2O from the atmosphere. Methane emissions varied from 1.1 mg C m-2 day-1 to 21 mg …

Effect Of Carex Rostrata Removal On Methane Emissions From A Temperate Peatland, Genevieve L. Noyce

Master's Theses and Capstones

Peatlands are a large natural source of atmospheric methane (CH4). Carex rostrata, a sedge species, has a critical role in the production, oxidation, and emission of CH4 from these systems. This study examined the changes in CH4 emissions from a temperate peatland after removing all aboveground C. rostrata biomass. Methane flux, dissolved CH4 concentration at various depths, C. rostrata green leaf area, temperature, and water table depth were measured from June 2008 to November 2010.

There is a strong positive correlation between C. rostrata green area and CH4 flux and the mean summer CH4 flux from the control plots was …

Interrelations Among Leaf And Canopy Nitrogen, Optical And Structural Traits, Franklin Brown Sullivan

Master's Theses and Capstones

A correlation between canopy nitrogen and albedo has been observed across a wide range of forest types. Determining the nature and mechanisms behind the relationship would help to understand the role of nitrogen in the climate system and better understand forest-climate interactions. The purpose of this study was to examine sources of variation in leaf and canopy optical traits with respect to variation in nitrogen concentrations at both scales.

We found that %N was significantly correlated with leaf and canopy albedo and that both %N and albedo were strongly correlated with forest composition. Many canopy structural traits were found to …

Saprotrophic Fungi As A Mechanism For Vertical Nitrogen Transport In A Chronically Fertilized Northern Hardwood Forest, Katharine M. Burnham

Master's Theses and Capstones

Decay studies often observe that plant litter increases in the amount of nitrogen within the first year of decomposition, yet sources are uncertain. The Harvard Forest Chronic Nitrogen Amendment Experiment, Petersham, MA, was utilized to quantify vertical N translocation from soil up into decomposing litter and determine if long-term, chronic N application has affected this process. Litter bags were designed to facilitate or restrict fungal hyphal connectivity between the soil-litter interface and placed in control, low N+S and high N plots. After five or 12 months, a 15N-(NH 4)2SO4 solution was horizontally injected into organic soil beneath bags. 15N enrichment …

A Feasibility Study: Forest Carbon Stocks And Stock Change Of The White Mountain National Forest, Erica Jane Cate

Master's Theses and Capstones

Interest has heightened for forest managers to account for the impacts of management activities on forest carbon sequestration. This study was designed to assess the feasibility of developing estimates of WMNF forest carbon based on the available information. The yield curves, inventory data and resulting carbon projections were dependent on a number of assumptions and subject to various sources of error and bias. Thus, they should not be relied on as definitive estimates and forecasts, or used as a basis for policy recommendations. Under the specific approaches used in this study, forest carbon stocks appear to be accumulating in the …

Hydrologic And Nutrient Dynamics In An Agriculturally Influenced New England Floodplain, Michelle Galvin

Master's Theses and Capstones

Non point-source pollution from agricultural activity is a major cause of water quality degradation. In particular, nutrient loading can lead to eutrophication and related anoxia in rivers, streams and lakes. Floodplains adjacent to these water bodies are sites of active nutrient cycling that can mediate the flux of nutrients to and from these water bodies. This study examines the hydrologic and nutrient dynamics of an agriculturally-influenced creek and floodplain in Lee, New Hampshire. Chemical mixing models were used to assess cycling of nutrients in response to flooding. The floodplain acted primarily as a sink for phosphate (PO43-), ammonium (NH4+) and …

Identifying Temporal Patterns And Controlling Factors In Methane Ebullition At Sallie's Fen, A Temperate Peatland Site, Using Automated Chambers, Jordan Goodrich

Master's Theses and Capstones

Despite leading to a potentially significant positive climate feedback, the processes controlling wetland methane fluxes remain relatively poorly understood. Automated chambers were employed in a temperate peatland site to quantify the timing and magnitude of methane ebullition (bubbling), one of the three pathways for wetland methane flux. The resulting datasets offer high temporal coverage of both components of this flux pathway, allowing for the first analysis of ebullition variability on seasonal, synoptic and diel timescales. The seasonal peak in ebullition occurred in August, likely due to high methane production rates and low methane solubility, both driven by temperature. Synoptic scale …

Modeling Permafrost Stability In Peatlands With Climate Change And Disturbance, Claire Treat

Master's Theses and Capstones

Boreal and arctic regions are predicted to warm faster and more severely than temperate latitudes. They contain large stocks of below- ground soil carbon in peatlands and frozen soil, and the flux of the soil C to the atmosphere may be a strong feedback to climate change.

Increases in air temperature due to climate change will increase surface soil temperatures, soil temperatures at depth, active layer depths, and growing season length, but not degrade permafrost by 2100 at this site. Both wildfire and climate change increase active layer depths by 25 cm, but effects of wildfire diminish following vegetation recovery.

Variation In Foliar Nitrogen And Albedo In Response To Nitrogen Fertilization And Elevated Carbon Dioxide, Haley F. Wicklein

Master's Theses and Capstones

It has recently been demonstrated that foliar nitrogen is positively correlated with surface albedo over a broad range of plant functional types. However, the mechanism(s) driving the nitrogen-albedo relationship remain elusive. This study investigated leaf spectral properties from three deciduous species subjected to either nitrogen or CO2 fertilization and compared results to measured chemical and structural properties. We measured reflectance and transmittance, foliar nitrogen, leaf mass per unit area, water content, and d13C values for stacks of 1, 2, 4, and 8 leaves. Nitrogen was the best predictor of leaf-level albedo of the traits that we measured. There were no …

Mycorrhizal Colonization And Nutrient Supply Rate Influence Elemental And Isotopic Tracers Of Calcium Cycling In Plant-Substrate Systems, Claire J. Hoff

Master's Theses and Capstones

Intraplant (root-foliage) fractionation of Ca isotopes and Ca/Sr were determined in Pinus sylvestris seedlings grown at different nutrient supply rates with or without ectomycorrhizal colonization. Foliar 44Ca/40Ca and Ca/Sr are uniformly higher than those of roots in individual seedlings, and these ratios in both foliage and roots differed significantly from those of nutrient sources. The measured offsets indicate that isotopic and trace element ratios can identify relative contributions from distinct calcium pools in terrestrial ecosystems. Furthermore, the results clearly show that fractionation of calcium isotopes and calcium from strontium in plants must be assessed in ecosystem-scale budgets and large watershed …

Separation Of River Network Scale Nitrogen Removal Among Main Channel And Two Transient Storage Compartments, Robert James Stewart

Master's Theses and Capstones

Reach scale experiments have shown that transient storage (TS) could be an important control on dissolved inorganic nitrogen (DIN) export to coastal waters. Here, the relative roles the main channel (MC), surface TS (STS) and hyporheic TS (HTS) have in DIN removal at the network scale are investigated using a model applied to the Ipswich River in Massachusetts. Collaborative field investigations in 1st through 5th order reaches of the Ipswich River provided the mean and range for the hydraulic parameters controlling TS connectivity and residence time. DIN removal was simulated in the MC, STS and HTS compartments for every river …

The Biogeochemical Influences Of Nitrate, Dissolved Oxygen, And Dissolved Organic Carbon On Stream Nitrate Uptake, Joseph A. Thouin

Master's Theses and Capstones

Streams are important hotspots for the retention and removal of nitrogen (N), an element that contributes to eutrophication and threatens the stability of coastal ecosystems. Nitrate (NO3-) is the most mobile form of N, and understanding the causal mechanisms that foster optimal NO3- retention and removal in stream systems is critical from both predictive and conservation standpoints. Dissolved organic carbon (DOC) is hypothesized to be a major control of instream NO 3- concentrations, but dissolved oxygen (DO) is also an important control of NO3- removal processes. Assessing the individual impacts of NO3-, DO, and DOC concentrations on stream NO3- removal …

Investigating The Free Amino Acid Contribution To Dissolved Organic Nitrogen Along A Flowpath In The Lamprey River Watershed, New Hampshire, Austin C. Stonebraker

Master's Theses and Capstones

Dissolved organic nitrogen (DON) is an important bioavailable source of nitrogen in terrestrial and aquatic systems. However, few studies quantify DON constituents such as dissolved free amino acids (DFAA) and investigate their concentrations along a hydrologic flowpath. Dissolved free amino acids and other water chemistry parameters were measured at different sites along the Lamprey River from September, 2006 to September 2007. The same analyses were performed on wet precipitation and throughfall samples within the Lamprey River watershed to represent a flowpath from atmosphere to surface waters to better understand nitrogen cycling within the watershed and speculate on possible influences. Ions …

Controls On Denitrification In A Northeastern Coastal Suburban Riparian Zone, Katherine Traer

Master's Theses and Capstones

Anthropogenic nitrogen (N) inputs in terrestrial and aquatic ecosystems can alter groundwater N cycling, which affects N fluxes in surface water and coastal environments. Increased N inputs can decrease the overall health of terrestrial and coastal ecosystems as well as pose serious human health threats. It is well documented that riparian zones can reduce N fluxes to surface water bodies as well as coastal environments. Recently, it has been determined that riparian denitrification potential is largely influenced by hydrogeologic characteristics.

Hydrogeologic characteristics and groundwater physical properties and chemical constituents were evaluated in the James Farm well field located in Lee, …

Field Efficiency And Bias Of Several Methods For Downed Wood And Snag Inventory In Western North American Forests, Robert Scott Kenning

Master's Theses and Capstones

Coarse woody debris (CWD)---downed forest wood and snags---has been afforded increasing attention in the past decade as studies illuminate the role of dead wood in the study of global carbon cycling, wildlife, forest fire, and soil ecology. Accordingly, the need for efficient sampling methods of CWD has grown. This study compares the field efficiency and bias of seven traditional and novel sampling techniques. Methods were tested in 14 forest stands across 3 broad study regions---alpine and ponderosa forests in Colorado and coastal rainforest in British Columbia.

For sampling downed wood volume, perpendicular distance sampling (PDS) proves to be the most …

Denitrification Drives Total Nitrate Uptake In Small Puerto Rican Streams, Jody D. Potter

Master's Theses and Capstones

An intensive study that was part of the Lotic Intersite Nitrogen eXperiment II (LINX II) project was conducted to determine nitrogen transformations in nine low-order streams with contrasting land use. Short term (24-hour) additions of K15NO3 and NaBr were performed on a gradient of anthropogenically impacted streams in Puerto Rico. Nitrate uptake was determined from longitudinal decline in 15NO3 and denitrification rates were determined from the longitudinal pattern of 15N 2 and 15N2O. Several physical, chemical, and biological variables were also measured to determine controlling factors. I performed these experiments to investigate: (1) the mechanisms for NO3 uptake and denitrification …

Consequences Of Fine-Scale Heterogeneity On Predictions Of The Carbon Cycle Using Lidar Data And A Height-Structured Ecosystem Model, R Quinn Thomas

Master's Theses and Capstones

To more accurately predict carbon stocks and fluxes in forests, it is important to measure fine-scale heterogeneity in ecosystem structure across the landscape, and incorporate the underlying mechanisms responsible for the observed heterogeneity in ecosystem models. This study used large-footprint lidar and a height-structured ecosystem model to estimate carbon stocks and fluxes at Hubbard Brook Experimental Forest (HBEF). At HBEF elevation gradients yield a decline in aboveground carbon stock, due to changes in net growth rates and disturbance at higher elevations. Lidar and a height structured ecosystem model can accurately quantified aboveground carbon stocks. Estimates of aboveground carbon fluxes depended …

Impacts Of Palustrine Wetlands On Surface Water Quality In The Lamprey River Watershed, New Hampshire, Shelby A. Flint

Master's Theses and Capstones

Surface water chemistry was measured monthly at ten wetlands in New Hampshire from January, 2005 through October, 2006. An additional wetland was sampled intensively and only during summer-autumn, 2005, and summer, 2006. Nitrate, ammonium, dissolved organic nitrogen, total dissolved nitrogen, nitrous oxide, and dissolved organic carbon concentrations in surface waters immediately up- and downstream of the wetlands were compared and changes in concentration were modeled. Nitrate, total nitrogen, organic nitrogen, and organic carbon concentrations differed significantly between upstream and downstream sampling stations. Ammonium and nitrous oxide did not show strong differences between upstream and downstream during much of the sampling …