Research

Impact of Agricultural Stream Restoration on Riparian Hydrology and Biogeochemistry
The primary objective of this research is to understand and predict the impact of river restoration in agroecosystems on surface water-groundwater (SW-GW) interactions and biogeochemical processes in the near-stream zone (hyporheic and riparian zones). Restoration approaches that aim to improve water quality by enhancing retention time and promoting reducing conditions may increase nitrogen removal via denitrification, but be achieved at the expense of phosphorus desorption and emission of greenhouse gases (GHG) (N2O, CO2, CH4). Through this project, we will test the hypotheses that (1) restored streams will have elevated water tables and prolonged, more extensive areas of reducing conditions compared to unrestored, (2) instream channel complexity will lead to higher denitrification rates, higher phosphorus concentrations in pore water via desorption, and increases in N2O and CH4 fluxes in restored compared to unrestored reaches, and (3) restoration approaches closely aligned with reference channel geomorphology will have greater SW-GW interactions and biogeochemical transformations. This work is conducted in collaboration with Dr. Philippe Vidon (co-PI, SUNY-ESF) and funded by USDA-AFRI – Processes and Transformation in Soil, Water and Air Program (5/2012-4/2015).
Influence of Stormwater BMPs on Stream Ecosystem Function
Ecosystem processes (nutrient uptake, metabolism, temperature and biological indices) are ideal measures of stream condition because they integrate environmental and landscape characteristics. Together with collaborators at UNC Charlotte (Sandra Clinton and Anne Jefferson) and at the University of California Santa Barbara (Christina Tague), we are integrating field based research and watershed scale ecological modeling to better understand and predict the cumulative effects of BMPs on receiving streams.  Through this research we will also help guide management decisions on placement of stormwater best management practices (BMPs) within a watershed and identify optimum locations for watershed restoration efforts. This work is funded by the National Science Foundation under Grant No. 1034043.
Nitrogen Retention in Restored Urban Streams
Stream restoration aims to provide stream stability while reestablishing ecosystem services, including diversity of plant and animal life, improved water quality and overall ecosystem function (e.g. nutrient processing, organic matter cycling and ecosystem metabolism). Our research focuses on ecologically based instream restoration elements that can potentially enhance nitrogen removal in previously degraded urban streams.  We are currently investigating the link between instream geomorphic features and nitrogen retention through a comprehensive approach of field assessment of stream morphology, quantification of whole stream nitrogen uptake and measurement of microbially mediated biogeochemistry (e.g denitrification and nitrification).  By including a range of restoration strategies and ages of restoration projects, this research will also improve our understanding of the recovery response of nitrogen retention after the restoration project is completed and as the ecosystem matures.  This work is funded by the North Carolina Water Resources Research Institute.
Linking Microbes and Ecosystem Processes in Restored Urban Streams
Together with collaborator Sandra Clinton, we are investigating the role that stream microbial communities play in nitrogen cycling, particularly how changes in environmental conditions and microbial populations affect denitrification in urban streams. Quantitative assessment of the effects of restoration elements (e.g. debris dams, riffle-pool sequences, rock weirs) on denitrification rates and populations of denitrifying bacteria in restored urban streams is largely untested.  We are currently measuring benthic microbial diversity in five urban streams with varying landscape histories using automated ribosomal spacer analysis (ARISA) and denitrifier diversity using terminal restriction fragment length polymorphism (TRFLP).  By applying molecular techniques to stream ecosystems we can begin to understand changes in urban stream microbial diversity and link these patterns to ecosystem processes. This work is funded by UNC Charlotte Faculty Research Grant Program.
Urbanization and Instream Temperature Pulses
The goal of this project is to develop a greater understanding of the dynamic nature of urban stream hydrology, including the response of stream temperature in streams with varying watershed areas and flow.  We are also interested in the effects of land use patterns on stream response, including the percentage of total versus directly connected impervious area. We are currently monitoring discharge and temperature at 4 urban watersheds in Winston-Salem, NC.  Streams range from perennial headwater streams to fourth order creeks and include both restored and impaired reaches.  This work is funded by the City of Winston-Salem, NC.
Hydroecological Modeling
Extension of restoration efforts to the watershed scale has tremendous potential through integration of stormwater best management practices (BMPs) with ecologically based restoration efforts.  Ecological models that couple biogeochemical and hydrological processes at the watershed scale can be used to identify nitrogen sources and areas for restoration.  We are interested in applying modeling tools to better understand and predict the effects of stormwater management and stream restoration on stream health at the catchment scale.  By building upon nutrient retention measured at the reach scale via nutrient spiraling methods and biogeochemical transformations at the mesocosm scale, we can extrapolate findings across larger spatial scales and better assist water resource managers in the placement of stormwater management and restoration projects on the landscape.  This work is funded by the UNC Charlotte ADVANCE Program.