Net ecosystem exchange of carbon over annual and perennial grasses following land use conversion

Michael Abraha, Jiquan Chen, Yahn-Su, Stephen K Hamilton, and G Philip Robertson
W.K. Kellogg Biological Station; CGCEO/Geography, Michigan State University

Presented at the All Scientist Meeting (2015-04-15 to 2015-04-16 )

Land use and land cover changes greatly influence surface characteristics and consequently the energy and mass exchange between the surface and the atmosphere. Recently, undisturbed lands and/or lands previously on conventional agriculture have seen land use changes towards biofuel crop production as part of climate change mitigation. In the US Midwest, grasslands that were recently recruited under Conservation Reserve Program (CRP) of the USDA and agricultural (AGR) lands are being rapidly converted for biofuel crop production in response to increased demand for biofuel feedstock. It is, therefore, important to investigate the net carbon balance of such land use conversions overtime, as this has direct implications on atmospheric CO2. Six fields – of which three had been managed under CRP and the other three under AGR – were converted to no-till soybean in 2009 and to no-till continuous annual (corn) and perennial (switchgrass and mixed-prairie) grasses from 2010 onwards. One additional CRP grassland was kept unchanged (brome grass) as a reference. We used eddy covariance (EC) technique to examine the temporal long-term dynamics (2009-2013) of carbon NEE in response to such land conversions and management practices. The EC observations revealed that converting existing grasslands into annual or perennial crop production result in a large carbon emission that may last several years after conversion.

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