Carbon dioxide exchange dynamics over a mature switchgrass stand |
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| Authors: | Elke Eichelmann Claudia Wagner‐Riddle Jon Warland Bill Deen Paul Voroney |
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| Affiliation: | 1. School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada;2. Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada |
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| Abstract: | Switchgrass (Panicum virgatum L.) has gained importance as feedstock for bioenergy over the last decades due to its high productivity for up to 20 years, low input requirements, and potential for carbon sequestration. However, data on the dynamics of CO2 exchange of mature switchgrass stands (>5 years) are limited. The objective of this study was to determine net ecosystem exchange (NEE), ecosystem respiration (Re), and gross primary production (GPP) for a commercially managed switchgrass field in its sixth (2012) and seventh (2013) year in southern Ontario, Canada, using the eddy covariance method. Average NEE flux over two growing seasons (emergence to harvest) was ?10.4 μmol m?2 s?1 and reached a maximum uptake of ?42.4 μmol m?2 s?1. Total annual NEE was ?380 ± 25 and ?430 ± 30 g C m?2 in 2012 and 2013, respectively. GPP reached ?1354 ± 23 g C m?2 in 2012 and ?1430 ± 50g C m?2 in 2013. Annual Re in 2012 was 974 ± 20 g C m?2 and 1000 ± 35 g C m?2 in 2013. GPP during the dry year of 2012 was significantly lower than that during the normal year of 2013, but yield was significantly higher in 2012 with 1090 g m?2, compared to 790 g m?2 in 2013. If considering the carbon removed at harvest, the net ecosystem carbon balance came to 106 ± 45 g C m?2 in 2012, indicating a source of carbon, and to ?59 ± 45 g C m?2 in 2013, indicating a sink of carbon. Our results confirm that switchgrass can switch between being a sink and a source of carbon on an annual basis. More studies are needed which investigate this interannual variability of the carbon budget of mature switchgrass stands. |
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| Keywords: | carbon balance CO2 flux cold climate ecosystem respiration eddy covariance gross photosynthetic production net ecosystem exchange switchgrass |
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