Biomass and Carbon Partitioning in Switchgrass

Frank, A. B.; Berdahl, J. D.; Hanson, J. D.; Liebig, M. A.; Johnson, H. A.

Biomass and Carbon Partitioning in Switchgrass

2004

Frank, A. B. | Berdahl, J. D. | Hanson, J. D. | Liebig, M. A. | Johnson, H. A.

Grasslands have an underground biomass component that serves as a carbon (C) storage sink. Switchgrass (Panicum virgatum L.) has potential as a biofuel crop. Our objectives were to determine biomass and C partitioning in aboveground and belowground plant components and changes in soil organic C in switchgrass. Cultivars Sunburst and Dacotah were field grown over 3 yr at Mandan, ND. Aboveground biomass was sampled and separated into leaves, stems, senesced, and litter biomass. Root biomass to 1.1-m depth and soil organic C to 0.9-m depth was determined. Soil C loss from respiratory processes was determined by measuring CO₂ flux from early May to late October. At seed ripe harvest, stem biomass accounted for 46% of total aboveground biomass, leaves 7%, senesced plant parts 43%, and litter 4%. Excluding crowns, root biomass averaged 27% of the total plant biomass and 84% when crown tissue was included with root biomass. Carbon partitioning among aboveground, crown, and root biomass showed that crown tissue contained approximately 50% of the total biomass C. Regression analysis indicated that soil organic C to 0.9-m depth increased at the rate of 1.01 kg C m⁻² yr⁻¹ Carbon lost through soil respiration processes was equal to 44% of the C content of the total plant biomass. Although an amount equal to nearly half of the C captured in plant biomass during a year is lost through soil respiration, these results suggest that northern Great Plains switchgrass plantings have potential for storing a significant quantity of soil C.

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