Soil food webs are complex assemblages of diverse species that couple mineral nutrient cycles in the soil to primary productivity of plants in root-zone ecosystems known as rhizospheres. These interactions link carbon from plant root exudates to a variety of predator-prey relationships that return excess nitrogen through mineralization to the growing plant. Previous work shows that the presence of predators in the rhizosphere food web can increase plant growth 50 to 150%. This project will use mass-isotope and molecular genetic techniques to identify processes involved in regulating these interactions. Work will be guided by a hierarchical mathematical model designed to predict how increases in atmospheric carbon dioxide and temperature influence carbon storage in the rhizosphere. Linkages between the carbon and nitrogen cycles in soil will be clarified by experiments under different levels of atmospheric carbon dioxide and temperature that move the ecosystem to new equilibria. One importance of this project lies in its contribution to the debate over whether additional carbon from increasing levels of atmospheric carbon dioxide can be stored in soil. Other aspects of the work will identify mechanisms that promote plant growth while sustaining beneficial interactions among bacteria, nematodes and mites that prey on nematodes.
