Measurements and Modeling of Carbon and Nitrogen Cycling in Agroecosystems of Southern Wisconsin: Potential for SOC Sequestration during the Next 50 Years |
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Authors: | Christopher J Kucharik Kristofor R Brye John M Norman Jonathan A Foley Stith T Gower Larry G Bundy |
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Institution: | (1) Center for Sustainability and the Global Environment, Institute for Environmental Studies, University of Wisconsin–Madison, 1225 Dayton Street, Madison, Wisconsin 53706, USA;,;(2) Department of Soil Science, University of Wisconsin–Madison, 1525 Observatory Drive, Madison, Wisconsin 53706, USA; and,;(3) Department of Forest Ecology and Management, University of Wisconsin–Madison, 1630 Linden Drive, Madison, Wisconsin 53706, USA, US |
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Abstract: | Landmanagement practices such as no-tillage agriculture and tallgrass prairie restoration have been proposed as a possible
means to sequester atmospheric carbon, helping to refurbish soil fertility and replenish organic matter lost as a result of
previous agricultural management practices. However, the relationship between land-use changes and ecosystem structure and
functioning is not yet understood. We studied soil and vegetation properties over a 4-year period (1995–98), and assembled
measurements of microbial biomass, soil organic carbon (SOC) and nitrogen (N), N-mineralization, soil surface carbon dioxide
(CO2) flux, and leached C and N in managed (maize; Zea mays L.) and natural (prairie) ecosystems near the University of Wisconsin Agricultural Research Station at Arlington. Field data
show that different management practices (tillage and fertilization) and ecosystem type (prairie vs maize) have a profound
influence on biogeochemistry and water budgets between sites. These measurements were used in conjunction with a dynamic terrestrial
ecosystem model, called IBIS (the Integrated Biosphere Simulator), to examine the long-term effects of land-use changes on
biogeochemical cycling. Field data and modeling suggest that agricultural land management near Arlington between 1860 and
1950 caused SOC to be depleted by as much as 63% (native SOC approximately 25.1 kg C m−2). Reductions in N-mineralization and microbial biomass were also observed. Although IBIS simulations depict SOC recovery
in no-tillage maize since the 1950s and also in the Arlington prairie since its restoration was initiated in 1976, field data
suggest otherwise for the prairie. This restoration appears to have done little to increase SOC over the past 24 years. Measurements
show that this prairie contained between 28% and 42% less SOC (in the top 1 m) than the no-tillage maize plots and 40%–47%
less than simulated potential SOC for the site in 1999. Because IBIS simulates competition between C3 and C4 grass species,
we hypothesized that current restored prairies, which include many forbs not characterized by the model, could be less capable
of sequestering C than agricultural land planted entirely in monocultural grass in this region. Model output and field measurements
show a potential 0.4 kg C m−2 y−1 difference in prairie net primary production (NPP). This study indicates that high-productivity C4 grasslands (NPP = 0.63
kg C m−2 y−1) and high-yield maize agroecosystems (10 Mg ha−1) have the potential to sequester C at a rate of 74.5 g C m−2 y−1 and 86.3 g C m−2 y−1, respectively, during the next 50 years across southern Wisconsin.
Received 28 December 1999; accepted 11 December 2000. |
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Keywords: | : prairie restoration carbon sequestration agroecosystems nitrogen budget IBIS land-use change |
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