Stephen C. Whalen

Whalen lab members:
  arctic ken                                          
   Ken Fortino

My research investigates the local and landscape scale factors that affect carbon cycling and organic matter storage in arctic lake sediments.  I focus my work on the northern foothills of the Brooks Range on the Alaskan North Slope.  The region is characterized by tundra vegetation and numerous small kettle lakes.  The lakes are typically very unproductive and are trophically supplemented by organic matter washed in from the watershed.  Once entering the lake, this organic matter is exported from the lake, buried in the sediments, or consumed and respired as CO2 by the lake biota.  The relative magnitude of each of these fates will determine the extent to which a lake is source or a sink of atmospheric CO2.  In general, the lakes tend to be a net source of atmospheric CO2, however considerable amounts of organic matter may be stored in lake sediments.  The processes that affect whether organic matter will be consumed or stored in lake are affected by local environmental factors (i.e., temperature and oxygen availability) and landscape scale factors (i.e., lake morphometry and organic matter transport).  My research is designed to elucidate how these factors interact to affect carbon cycling and organic matter storage in the lake sediments and how they may change with climate warming.

   Joelene Diehl

    I am a second year graduate student working toward a Master’s Degree in Environmental Science. My research project is on nitrogen  cycling and transformations that occur in agricultural soil treated with UAN fertilizer amended with urease and nitrification inhibitors. A majority of my work is spent in the lab conducting experiments on soil that I collected from Open Grounds Farm in Beaufort, NC. As a part of this research I conduct nutrient analyses on the soils and look at changes in the microbial community. Before entering the graduate  program at UNC-CH, I received a BS in Biology/Zoology from Eastern Washington University         and spent a couple of years in the Peace Corps.


Dendy in creek    Dendy Lofton

    My research examines benthic production of methane in Arctic Alaskan lakes and how methane derived carbon may be made available to pelagic organisms.  I am particularly interested in the factors controlling methane production and oxidation.  Methane is produced in anaerobic sediments as a byproduct of organic matter degradation. As this methane diffuses from the sediments, it becomes available to methane oxidizing bacteria where it is oxidized to carbon dioxide.  This methane derived carbon can be an important source of carbon for pelagic food webs.  Methanogenesis and subsequent oxidation represent an important link between benthic and pelagic food webs that has until recently been overlooked in limnological studies.  This study also has important implications for global warming because methane is a powerful greenhouse gas.  Any methane that is not oxidized in the lake can diffuse into the atmosphere where it will contribute to the global methane budget.  It is important to establish a foundation for these processes in the Arctic region in order to understand how they will be affected as global warming continues.

Lindsay   Lindsay Dubbs

    My Ph.D. research is primarily conducted at the FACTS-1 research facility in the Duke Forest where the atmospheric concentration of carbon dioxide within forest plots is maintained at present (control) and two-times preindustrial (elevated) concentrations via free air carbon exchange (FACE) technology.  My research investigates whether the previously observed reduction in net methane consumption by forest soils is a sustained response to elevated carbon dioxide, and examines reasons for the observed decline. I am interested in physical, chemical, and microbial community composition differences between elevated and control plots that may influence rates of methane consumption or production. I am also interested in reconciling problems arising from heterogeneity in soil properties and processes, and anoxic microsites. I conducted my MS thesis research as a member of the Whalen lab as well, and attended Tufts University for my BS. My MS thesis is entitled Seasonal Analysis of the Influence of Nutrient Reduction on Phytoplankton Biomass and Primary Production in the Middle Cape Fear River, NC.   


   Gina Trevino

           My research deals with nitrogen transport and fate in a large, precision managed, agro ecosystem. More specifically in determining rates of transport and eventual fate of N at Open Grounds Farm (OGF) which is a 45,000 acre farm located along the coast of North Carolina and is the largest farm east of the Mississippi River. I am particularly interested in trying to develop a nitrogen mass balance for the agricultural ecosystem and determining the relative quantities and forms of N (specifically NO3, NH4 and urea) found in both the agricultural soil and groundwater.  Also in trying to determine if differences exist between management practices that control moisture levels and in determining rates of N loss via volatilization and plant uptake to use in conjunction with N quantities found in soil and groundwater to estimate the amount of N being transported to the estuary.  It is my intention to use the data from the prior objectives to model the transport, transformation, and attenuation of NPS N from the agroecosystem (both soil and groundwater nutrient data) using GIS analysis in conjunction with BME/MATLAB modeling software and create a management budget for the ecosystem.  Determining nitrogen quantities in ecosystems is important because inorganic forms of nitrogen that are not taken up by plant matter can be leached out into the system or nitrified back into the atmosphere promoting pollution in ground and surface water and an increase in the greenhouse effect.  Determining rates of fate and flux of N at OGF is important because it does use precision agriculture (sometimes called best management practices) and it is essential to see if BMPs allow for efficient plant production and nitrogen uptake without promoting excess N in the environment and if these practices can be applied to future management.