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Impacts of Photodegradation on Decomposition of Plant Litter in Arid and Semi-Arid Environments
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Changes in stratospheric ozone levels, precipitation patterns, and plant canopy cover all have the potential to alter the rates of incident ultraviolet-B radiation reaching the Earth's surface. We are investigating the role of ultraviolet radiation exposure on surface decomposition of plant litter in arid and semi-arid environments where abiotic factors controlling decomposition may be as important or more important than biotic factors due to the high altitude, low plant canopy cover, and dry conditions of these regions. Results from a 3-year field study in Colorado demonstrate that photodegradation may account for a significant fraction of decomposition in shortgrass steppe (see Brandt et al. 2007). We are currently conducting a large-scale field experiment to examine the importance of photodegradation across a latitudinal gradient at sites in New Mexico, Colorado, and Minnesota.
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Collaborators: Leslie Brandt (Ph.D. student, University of Minnesota), Daniel Milchunas, William Parton, and Carol Adair (Colorado State University), Robert Sinsabaugh (University of New Mexico), Sarah Hobbie (University of Minnesota). Project supported by NSF Ecosystem Science.
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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. 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 peri-urban region represented by the environs of Cedar Creek Natural History Area approximately 35 miles north of the Twin Cities.
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Collaborators: Sarah Hobbie, Joe McFadden, Larry Baker, Kristen Nelson, Cinzia Fissore (all University of Minnesota). Projects supported by NSF Dynamics of Coupled Natural and Human Systems and NSF Long Term Ecological Research (LTER) at Cedar Creek.
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Impacts of Agricultural Management on Trace Gas Fluxes and Soil Carbon and Nitrogen Dynamics
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Human management of agricultural systems has important impacts on crop productivity, soil fertility, and ecosystem biogeochemical cycling. We are investigating the impacts of alternative management strategies on greenhouse gas exchange (CO2, CH4, and N2O fluxes) at a long-term field experiment site located at the Southwest Research and Outreach Center of the University of Minnesota (SWROC). Using 13C- and 15N-labeled plant residue inputs, we are tracing the turnover and fate of organic matter in soils under different agricultural management systems. Our overall objective is to advance our understanding of the impacts of crop management on soil carbon and nitrogen cycling and soil-atmosphere exchange of greenhouse gases.
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Collaborators: Harriet Van Vleck (Ph.D. student), Deborah Allan, Jay Bell, Jeff Strock, Karina Fabrizzi (all University of Minnesota). Project supported by the USDA-NRI Managed Ecosystems Program.
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The influence of drainage on biogeochemical cycling of carbon in agricultural
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Landscape drainage is a common feature in many agricultural ecosystems; this is especially true in the Midwestern United States. The effects of changing water flow paths on biogeochemical cycling of carbon, however, is 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.
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Collaborators: Brent Dalzell (Postdoctoral Associate), David Mulla, Gary Sands, Jacques Finlay (all University of Minnesota). Project supported by the USGS and the University of Minnesota Water Resources Center.
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Understanding Carbon Pools and Processes in Peatland Watersheds |
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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.
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Collaborators: Peter Weishampel (Postdoctoral Associate, University of Minnesota), Randy Kolka (USDA Forest Service). Project supported by the USDA Forest Service.
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