Controls on the Plant-Soil Stoichiometry of Dryland Agroecosystems: A Sabbatical Strengthening Grant

Drylands cover ~30% of the terrestrial land surface, serve as the base of extensive agricultural production practices in these regions, and contribute substantially to global biogeochemical cycling. Yet fundamental unknowns exist concerning controls on dryland biogeochemistry - such as the role of ultraviolet radiation in litter decomposition, the consequences of woody plant encroachment, effects of eutrophication and interaction with drought, and impacts of pasture diversification and incorporation of legumes. The goal of this year-long sabbatical strengthening proposal is to increase our understanding of these various dryland biogeochemical processes by exploring them in oak savannas of Portugal. We will utilize existing collaborations and on-going projects, as well as, initiate a new study to accomplish this goal. Objectives include: 1) Quantify how nutrient enrichment, shrub encroachment, drought, ultraviolet radiation, and pasture improvement impact plant litter and soil organic matter C:N:P ratios; and 2) Evaluate the ability of DAYCENT to model the effects of these controlling parameters on dryland biogeochemical cycling. This sabbatical award will: 1) provide the opportunity for PD McCulley to diversify her dryland agroecosystem research experiences; 2) create new knowledge regarding the ecological controls on the stoichiometry of these systems; and 3) provide possibilities for improvement of DAYCENT, a process-based biogeochemical model. This work addresses program area priorities of enhancing environmental quality and the natural resource base upon which the agricultural economy depends (renewable energy, natural resources, and environment) and improving our understanding of the linkages between processes and management actions that together impact the long-term sustainability of agroecosystems.