|Rogers Jr, Hugo|
|Prior, Stephen - Steve|
Submitted to: Department Of Energy Annual Report
Publication Type: Other
Publication Acceptance Date: 3/26/2003
Publication Date: 3/26/2003
Citation: Rogers, H.H., Pricthard, S.G., Davis, M.A., Prior, S.A., and Schlesinger, W.H. 2003. Carbon storage in CO2-enriched plant systems. Environmental Sciences Division: Summaries of Research in FY 2002. U.S. Department of Energy, Germantown, MD. 4pp. Interpretive Summary: The rise in atmospheric CO2, due mainly to fossil fuel combustion and land use change, is an undisputed fact. This ongoing CO2 increase has important implications for terrestrial carbon processes. Understanding the impact of increasing CO2 on plant and ecosystem productivity as well as the role of plants in mediating carbon flux between atmosphere and soil is hindered by a lack of knowledge about root dynamics (production and mortality). Of all ecosystem components, understanding the dynamics of fine root production is perhaps one of the most important, most difficult to study, and least understood. Information collected to date in three systems (an agricultural management study, a maturing forest site, and in a model regenerating forest competition study) support the contention that root net primary productivity will be enhanced in a higher-CO2 world.
Technical Abstract: Carbon cycling is being changed directly as a result of rising atmospheric CO2 concentrations, and indirectly through the effects of this extra CO2 on the metabolism of vegetation (CO2 fertilization). Although it has been suggested that terrestrial ecosystems of North America are functioning as a large sink for atmospheric CO2. Recognition that the distribution of root systems in space and through time is one of the most important components of terrestrial C cycling, and perhaps the entire global C cycle, is fast emerging. We are using minirhizotrons to provide information about how increasing CO2 will impact fine root dynamics plant systems. This progress report provides a summary of work in three studies: (1) agronomic management systems, (2) a maturing loblolly pine forest system (Duke FACTS-1 FACE site), and (3) forest competition in a model regenerating longleaf pine community. Early results from the agronomic systems indicate that in conventional plots, CO2-enrichment increased sorghum seasonal root production and mortality by 58% and 59%, respectively. Crop root growth, however, was unaffected by [CO2] in sustainable plots. Data emphasize the importance of quantifying production and mortality as separate processes. This study suggests that conversion from conventional to sustainable management might negate positive affects on root growth, at least in the C4 crop sorghum. In the maturing loblolly pine study, results from this study suggest modest, if any, increases in ecosystem-level root productivity in CO2-enriched environments. First year data from the forest competition study show that CO2-enriched plots exhibited 35% higher standing root crop length, 37% greater root length production per day, and 47% greater root length mortality per day. These variables, however, were enhanced by CO2 enrichment only at the 10-30 cm depth.