Life Sciences Commons^™

Climatic Range Filling Of North American Trees, Benjamin Seliger

Electronic Theses and Dissertations

Understanding the degree to which species distributions are controlled by climate is crucial for forecasting biodiversity responses to climate change. Climatic equilibrium, when species are found in all places which are climatically suitable, is a fundamental assumption of species distribution models, but there is evidence in support of climate disequilibria in species ranges. Long-lived, sessile organisms such as trees may be especially vulnerable to being outpaced by climate change, and thus prone to disequilibrium. In this dissertation, I tested the degree to which North American trees are in equilibrium with their potential climatic ranges using the ‘range filling’ metric, which …

The Effects Of Seasonal Variations In Chemistry And Hydrology On The Microbial Community And Its Sulfide Oxidation Potential In A Naturally Acidic Maine Stream, Raymond C. Kahler Iii

Electronic Theses and Dissertations

Sulfide minerals oxidize through interaction with water and oxygen, releasing hydrogen ions. The process often occurs naturally near metal sulfide deposits, and can be accelerated through mining. Microorganisms accelerate the rate of sulfide oxidation. Acidified streams typically contain high metal concentrations (e.g. aluminum) and microbes in these systems may develop resistances to metal toxicity. Stream flow can affect sulfide oxidation and microbial community structure. Baseflow can influence stream chemistry from interactions with the surrounding bedrock, while stormflow affects stream chemistry and the local microbial community through dilution and addition of microbes transported by runoff. Microbial community composition is affected by …

Nitrogen Cycling During A Period Of Environmental Change, Kaizad Patel

Electronic Theses and Dissertations

Natural and anthropogenic disturbances have altered the N cycle on the regional to global scale. Although numerous studies have examined the effects of chronic atmospheric N deposition on ecosystem processes, less is known about intra-annual variability of these processes, or how these responses might be altered under conditions of changing climate. The work described in this dissertation focuses on the effects of a changing chemical and physical climate, particularly terrestrial N processes (a) during Maine’s changing winters, and (b) in response to chronic elevated N additions.

Subnivean winter soil processes were examined at the Dwight B. DeMerritt Forest (DBDF) and …

Developing A Risk Assessment Protocol To Quantify Distribution And Uptake Of Persistent Organic Pollutants In Glacial Outflows, Kimberley Rain Miner

Electronic Theses and Dissertations

Pollutants released by industrialized nations between 1960 and 2004 have been transported northward through atmospheric processes and deposited into glaciated alpine ecosystems. Many of these chemicals retain their original structure and are absorbed into the biota thousands of miles away from where they were originally utilized. With a warming climate increasing the melt of alpine glaciers, these glaciers may be introducing growing amounts of toxins into the watershed. While studies have demonstrated the existence of resident pollutants within glaciated ecosystems, no one has developed a risk assessment to identify sources and quantity of risk posed by these compounds when released …

Reducing Tillage In Small-Scale Permanent Bed Organic Vegetable Production Systems, Jeremiah D. Vallotton

Electronic Theses and Dissertations

The response of field-grown vegetable crops to reduced tillage and mulching in permanent beds was evaluated through measuring crop yields, weed pressure, earthworm counts, and soil basal respiration. Two vegetable crops (“Bush Delicata” squash and “Farao” cabbage) were started in April and May of 2016 and 2017 respectively, transplanted in late June, and harvested on 15-Sep-2016 and 25-Aug-2017. Fruit number and weight of squash, and head weight and feeding damage of cabbage were measured. These results suggest that intensive tillage (8” rototill every year) can be successfully reduced to alternating years of shallow (2”) rototilling and a less intensive form …

Detrital Protein Contributes To Oyster Nutrition And Growth In The Damariscotta Estuary, Maine, Usa, Cheyenne M. Adams

Electronic Theses and Dissertations

Oyster aquaculture is an expanding industry that relies on identifying and utilizing natural estuarine conditions for the economically viable production of a filter-feeding crop. The eastern oyster, Crassostrea virginica, is the principal species currently cultured in Maine. In addition to preferentially consumed phytoplankton, various detrital complexes (non-algal and/or non-living organic matter) may provide some nutrition to C. virginica between times of phytoplankton abundance. Here I investigated the importance of detrital proteins in supporting the growth of oysters cultured in the upper Damariscotta Estuary. Oyster aquaculture in this area is highly successful and previous reports indicate that labile detrital protein …

Impacts Of Diverse Crop Rotations And Integrated Crop-Livestock System On Soil Quality In South Dakota, Atilla Polat

Electronic Theses and Dissertations

Crop diversification can be beneficial in improving soil quality parameters. Diverse crop rotations and integrated crop-livestock systems (ICLS), are two examples of crop diversification used in this study to assess soil quality. The objectives of this study were to: (i) assess the impacts of diverse rotations on soil quality parameters, and (ii) assess the impacts of low and high stocking density on soil quality parameters. Both of the studies were conducted separately and are presented as two different chapters. To accomplish objective (i), a long-term experiment was selected which was established near Brookings, South Dakota, USA at USDA-ARS lab in …

Modeling Soil Organic Carbon In Select Soils Of Southeastern South Dakota, Shaina Westhoff

Electronic Theses and Dissertations

Soil organic matter (SOM) is composed of living biomass, dead plant and animal residues, and humus. Humus is a class of complex, organic molecules that are largely responsible for improving soil water holding capacity, nutrient mineralization, nutrient storage, and other critical soil functions. Soil organic carbon (SOC) accounts for approximately 60 percent of SOM and thus SOC is recognized as a strong indicator of soil health. Land use changes and intense cultivation of arable soils in the United States over the past century have led to large decreases in SOM. The objective of this research was to develop a multiple …

Quantifying The Short-Term Impacts Of Cover Crops And Grazing On Soil Health Under An Integrated Crop-Livestock System In South Dakota, Vishal Seth

Electronic Theses and Dissertations

Cover crops and grazing under Integrated Crop-Livestock System (ICLS) can impact the rhizosphere nutrient cycling and may have potential to increase the long-term sustainability and economic profitability of agricultural production system. In South Dakota, crop production practices and livestock husbandry are both common which provide the opportunity for ICLS to be successful in this region. However, little is known about the impacts of the cover crops and grazing under ICLS on soil properties in this region. The present study was conducted at South Dakota State University Research Farm (44°20'34.8"N, 96°48'14.8"W), Brookings, SD, to quantify the impacts of cover crops and …

Land Use Change Sustainability And Carbon Turnover Rate In The Northern Great Plains Soil, Deepak Raj Joshi

Electronic Theses and Dissertations

Sustainable land management involves the management of land, water, biodiversity and other resources that meet human requirements while maintaining ecosystem services. In the northern Great Plains (NGP), the combined impacts of landuse and climate variability have placed many soils at the tipping point of sustainability. The objectives of this study were to: 1) calculate land-use changes from 2006 to 2012 and from 2012 to 2014 in South Dakota and Nebraska; 2) assess if land use changes had impacted on soil sustainability; 3) calculate variation in total carbon budget and turnover due to seasonal climate variability, biomass quality and soil properties; …

Greenhouse Gas Emissions From Soil Applied Nitrogen Fertilizers, Samuel Thies

Electronic Theses and Dissertations

Greenhouse gases (GHG) absorb and emit radiant energy in the thermal range. Their concentrations in the atmosphere are increasing and becoming an ever increasing issue as the Earth’s average temperature continues to rise. Agricultural practices, such as applying nitrogen fertilizer to increase crop yield can be a major source of GHG emissions and methods are needed to decrease these emissions. The measurements of GHG emissions have been difficult, expensive, and erratic. However, advancing technologies have increased the accuracy and confidence in measuring GHG emissions. The objectives of this study were to determine the 1) effects of different nitrogen fertilizer sources, …