Current Research Projects
Floodplain Denitrification
Modern increases in anthropogenic nitrogen loads in streams and rivers, and resultant downstream eutrophication, have underscored the need to identify practices that promote nutrient retention in these ecosystems. I am working to determine the role floodplain wetland restoration and the reinstatement of river-floodplain interaction can play in promoting denitrification and lowering river nitrogen concentrations. Floodplain wetlands in agricultural settings can have high denitrification rates related to hydric soils, carbon availability from vegetation and nitrogen availability from groundwater and overbank flooding. My work focuses on determining what controls spatial patterns of denitrification, improving prediction of denitrification rates within a watershed and determining how floodplain restoration, backwater reconnection, or flow regulation may promote favorable patterns in denitrification.
In-channel Nutrient Dynamics
In collaboration with colleagues at the National Center for Earth-Surface Dynamics (NCED) and through the UC Berkeley Angelo Coast Range Reserve, I am working in a paired set of experiments in a field setting and a field-scale flume to determine the role geomorphic form plays in constraining the uptake and retention of biologically important nutrients in streams. In the flume I have found that the texture and composition of benthic sediment and presence or absence of biofilm can profoundly change water transport rates and exchange with hyporheic zones. These variations in flow paths allow for large differences in microbially-mediated nutrient uptake and transformation as water is preferentially routed through surface or subsurface 'hotspots' under different bed configurations. Recently I have been applying findings from the flume to natural geomorphic gradients in the Eel River watershed in northern California to help explain variation in nutrient uptake previously observed there.
Stream Restoration
One of my main research foci is determining of how physiographic setting controls ecosystem processes in aquatic systems. Restoration projects are opportunities to study these links through experimental manipulation conducted in the context of a particular geomorphic setting and with a particular ecosystem function to be rehabilitated. My motivation for working with restoration projects is to determine how physical parameters which are commonly changed during restoration impact basic ecosystem functions such as primary productivity, nutrient uptake and retention, and vegetation establishment. In addition to improving our basic understanding of aquatic systems, knowing more about these interactions will allow us to design restoration projects which promote favorable and sustainable ecosystem functions. I have approached these goals chiefly by studying dam and levee removal, but the concept can apply to any restoration activity. Currently I am working with collaborators at NCED to design related experiments in a new outdoor flume facility being built at the St. Anthony Falls Laboratory in Minneapolis, MN.
From Wayne Wurtsbaugh via the ASLO image library.