Past Research Projects

Investigating the Controls on Biogeochemistry of Urban Ecosystems

Despite the growing importance of cities as biogeochemical hotspots, little is known about factors influencing elemental fluxes through the individual households that make up a large fraction of urban areas. We have recently conducted a study of household biogeochemical cycling of carbon, nitrogen, and phosphorus (supported by NSF Coupled Biogeochemical Cycles). Through this study we identified the key household fluxes and developed the Household Flux Calculator (HFC) in order to examine variations among households (see Baker et al. 2007). With new funding, we are extending this work further to quantify household carbon, nitrogen, and phosphorus fluxes among households in the Twin Cities Metropolitan Region and to examine the influence of human choice on these fluxes. A large survey of the urban region has resulted in a large database of information on biogeochemical fluxes and numerous biological, physical, and social factors that may influence biogeochemical fluxes. We are also investigating the effects of land use conversion on ecosystem function using a chronosequence of sites along a gradient between the Twin Cities urban area and the ex-urban region represented by the environs of Cedar Creek Ecosystem Science Reserve approximately 35 miles north of the Twin Cities.

Collaborators: Cinzia Fissore (Whittier College), Sarah Hobbie, Larry Baker, Kristen Nelson (University of Minnesota); Joe McFadden (UCSB). Projects supported by NSF Dynamics of Coupled Natural and Human Systems and NSF Long Term Ecological Research (LTER) at Cedar Creek.

Examining the Impacts of Agricultural Drainage on DOC Losses

Landscape drainage is a common feature in many agricultural ecosystems; this is especially true in the Midwestern United States. However, the effects of changing water flow paths on biogeochemical cycling of carbon are poorly understood. In this study, we are investigating the effects of subsurface drainage (commonly called tile drainage) on the quantity and quality of organic carbon exported from agricultural fields. Results from this research will help us to understand which processes are biogeochemically important in controlling the communication between upland ecosystems and the streams (and ditches) that drain them.

Collaborators: Brent Dalzell (Postdoctoral Associate), David Mulla, Gary Sands, Jacques Finlay (University of Minnesota). Project supported by the USGS and the University of Minnesota Water Resources Center.

Understanding Carbon Pools and Processes in Peatland Watersheds

Much of the terrestrial carbon work done in forested systems has focused on upland systems whereas little work has addressed wetland systems, especially peatland systems where nearly 30% of global soil carbon storage exists. We are investigating carbon pools and processes in peatland watersheds in northern Minnesota and Wisconsin. The sites include the USDA Forest Service Marcell Experimental Forest located in north-central Minnesota and the Chequamegon National Forest in central Wisconsin. We are conducting measurements of carbon pools, hydrologic fluxes and gaseous fluxes (CO2 and CH4) from both upland and peatland components of the watershed. We are developing an inventory of aboveground and belowground carbon pools. These measurements will advance our understanding of carbon cycling dynamics in peatland ecosystems. As part of the North American Carbon Program (NACP), this project will provide critical information for developing landscape scale estimates of carbon budgets (see Weishampel et al. 2009).

Collaborators: Peter Weishampel (Northland College), Randy Kolka (USDA Forest Service). Project supported by the USDA Forest Service.

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