Carbon Storage in Plant and Soil Components of Selected Grass Monocultures.

Carbon (C) sequestration and storage in grassland monocultures has profound implications in the utilization of grasslands for biofuels as well as mitigating the impacts of CO₂ on global warming.  We compare the differences between three warm-season native (C₄) species and two introduced cool-season (C₃) species monocultures grown for > 15 years for seed and forage production on land that was previously in crop production.  The grasses were sampled at or shortly after anthesis for aboveground biomass production as well as for root biomass production in the upper 0.6 m of the soil profile. The grass materials were separated into standing vegetation, dead or residue on the soil surface and roots in the surface 60 cm of the soil. Plant materials and soil were analyzed for C and the distribution of the C between plant materials and soil were determined.  The proportion of soil C as part of the monoculture system ranged from 95.5 to 97.9 percent of the total organic C with an average of 96.8 percent of the C as soil organic matter.  Under the conditions of the grass management system in this study, harvesting plant biomass for biofuel production is unlikely to cause a decline in soil C if the grass is properly managed.