Linking above- and belowground responses to rising CO2 in northern deciduous forest species

Results from two years' work with Populus in a northern forest ecosystem has provided broad support for our conceptual model of above- and below-ground linkages through C and N cycling within the plant-soil system. They have also supported our working hypothesis that rising CO2 will lead to positive feedback within this system, resulting in increased N mineralization and plant N acquisition. These conclusions must be qualified by the short duration of these experiments and the likelihood that negative feedback may only appear over longer time spans. We also have limited knowledge of the dynamics of C movement from plant to soil and of N transformation within the soil. We hope to address each of these shortcomings within the long-term exposure study set to begin in 1994.