Spring 2016 Seminar Series
20 January | 375 Borlaug Hall | 3:30 PM
Nitrous oxide (N2O) is a major greenhouse gas and is a significant contributor to ozone layer destruction. Agricultural soils and runoff-receiving water are considered significant sources of N2O. N2O can be produced as the end or intermediate product of denitrification or as the byproduct of nitrification. N2O can also serves as an electron acceptor for microbial respiration (i.e., N2O reduction). The balance between N2O production and reduction influences the overall emission of N2O. Therefore, to mitigate N2O emission from soil and water, it is important to identify when, where, and under what conditions these reactions actively occur, and which microbes are responsible for these reactions. I have used various analytical, microbiological, and genomic tools to answer these questions. In this presentation, I will share my recent research done using real-time gas-monitoring analysis, 15N stable isotope analysis, denitrification functional gene transcriptome analysis, and microscale N2O concentration measurements. I will also introduce some of my ongoing research related to the N cycle.
3 February | 375 Borlaug Hall | 3:30 PM
Water possesses many special properties that give it a pivotal role in natural systems, human systems, and inter-system linkages. These properties also make water resource systems complex and multifaceted, leading to an array of challenging questions facing policy makers, businesses, and households. The University of Minnesota is already known as a leader in addressing water resource questions through frontier discoveries and actionable science. This seminar will begin a conversation about the ways that the University can expand and deepen its contributions to the science and management of water resources. The Water Resources Center, as an interdepartmental unit, is positioned to serve a catalyzing role to help faculty and students take advantage of opportunities and forge connections inside and outside the institution.
To watch a recording of the presentation, click here.
17 February | 375 Borlaug Hall | 3:30 PM
Dr. Monica Palta | Arizona State University
Nitrogen (N) removal is commonly cited as a rationale for wetland restoration and construction projects because wetlands have demonstrated the ability to prevent movement of excess N from uplands into surface water. The ability of wetlands to remove nutrients from surface water is of particular importance in urban areas, where atmospheric N deposition is high and dense human populations generate high inorganic N concentrations in surface water and groundwater. The conversion of nitrate (NO3-) to inert N2 gas via the microbial process of denitrification, which typically occurs at high rates under natural wetland conditions, is therefore a process of interest to water resource managers in cities. Urban landscapes contain many types of water bodies, all of which may have varying potential for N removal, carbon (C) sequestration, and greenhouse gas (N2O, CO2, CH4) emissions. My work demonstrates that the rates and end products of denitrification in urban wetlands are mediated by a complex combination of edaphic and hydrologic components that vary over space and time. For example, water content and soil pore structure mediate soil oxygen, and therefore both denitrification, a suboxic process, and nitrification, an aerobic process that creates NO3-. Denitrification is often coupled with nitrification, so when soil oxygen is too low, denitrification may no longer occur. Under suboxic conditions, N2 is the primary end product of denitrification, but denitrification can also result in the release of nitrous oxide (N2O), depending on soil chemistry and soil oxygen levels. I will be discussing studies that I have conducted in both the Northeastern and Southwestern U.S. examining how soil structure, soil-water dynamics, and hydrology mediate both N removal and potential greenhouse gas production in urban wetlands.
To watch a recording of the presentation, click here.
2 March | 375 Borlaug Hall | 3:00 PM
The ocean covers over 70 percent of Earth's surface area, has accommodated nearly one-third of anthropogenic CO2 emissions, and accounts for nearly one-half of global primary production. Over the past decade, satellite observations have revealed a strong positive correlation between ocean chlorophyll and the number concentration of cloud droplets, highlighting a critical link between ocean biogeochemistry and climate. Early work in this field suggested that either oceanic emission of dimethyl sulfide or changes in the production rate of sea-spray aerosol particles during wave breaking may provide this connection. In this talk I will use a combination of observations from a series of oceanic research cruises and laboratory experiments conducted in a wave channel to explore two emerging hypotheses that may serve to connect ocean chemistry with cloud formation: 1) reaction products formed from the gas-phase oxidation of marine-derived terpenes play a controlling role in altering the size distribution of aerosol particles in marine environments, and 2) the chemical composition of nascent sea-spray aerosol, and the resulting ability for the particle to serve as a cloud condensation nuclei, is a strong function of chemical and biological processes occurring at the ocean surface.
30 March | 375 Borlaug Hall | 3:30 PM
15 April | 375 Borlaug Hall | 2:00 PM
Dr. Jerry Hatfield | Laboratory Director, National Laboratory for Agricultre and the Environment; Director, Midwest Region Climate Hub, Ames, IA
Understanding the Long-term Dimensions of Agricultural System Change: A View from Polynesian Environmental Archaeology
27 April | 375 Borlaug Hall | 3:30 PM
Agriculture has been a fundamental activity of our species for the last 10,000 years. Throughout the world, agricultural systems have responded to a diverse set of social and environmental factors that have directed, constrained, or presented opportunities for their evolution. At the same time, developments in agricultural systems have resulted in drastic environmental and social change. Understanding this reciprocal relationship has become a key topic of research for environmental archaeologists. In this talk, I will present a conceptual framework for understanding these human-environmental relationships based on empirical research in the Polynesian archipelago of Samoa. Islands have been identified as model systems for the examination of human-environmental relationships, given their general isolation and small size, and sequences of agricultural change are not well documented throughout the region. By exploring the relationship between human cultural practices, climate, and the environment here, important information may be gleaned to inform modern agricultural practices and environmental change.
4 May | 375 Borlaug Hall | 3:30 PM
Hydrologic impacts due to alterations of land use and management for agriculture have been implicated in surface and groundwater quality and quantity concerns. What remains poorly understood, however, is the influence of agricultural management practices on field and landscape-scale water budgets. In this talk I will share results from two years of field data collection and modeling aimed at understanding and quantifying the impact of subsurface drainage practices on water budgets for corn production systems. The field research was conducted at three sites which extend along an east-west precipitation gradient from eastern South Dakota (SD) to central Minnesota (MN). Average annual precipitation for the study sites ranges from approximately 584 mm in eastern SD to over 762 mm for south-central MN. Direct and indirect measurements of the soil water balance will be compared and contrasted. Results of this research will provide important information that will allow farmers, land managers and water management system designers to design water management infrastructure in ways that are both effective for production and environmentally responsible.