Annual grasses, perennial grasses, and blue oaks all share space within the California Sierra Foothills Oak Woodland ecosystem. Below ground these plant communities have the opportunity to become joined by a common arbuscular mycorrhizal network. During the winter months of this Mediterranean type climate, grasses are actively growing and competing for nutrients. As temperatures rise in the spring, blue oaks leaf out and begin to photosynthesize while grasses start the progression from flowering, to seed filling, and eventual senescence. Competition and demand for nutrients above-ground shift throughout the season, and movement through below-ground connections should reflect these changes. We are interested in how N and K are transferred among the annual and perennial plants. In particular: Do grasses transfer more N to surrounding plants while senescing? How competitive are oaks? And, are transfers of N and K linked? Three identical greenhouse experiments examined the movement of 15N-urea and rubidium (a chemical analog of potassium) between donor and receiver plant shoots, with each experiment at a different grass life stage; vegetative, flowering, and seed filling/senescing. Donor and receiver plants were restricted to hyphal connections by employing double root restrictive screens separated by a 0.5-1.0 cm air-gap to prevent chemical soil diffusion between chambers. An annual grass (Bromus hordeaceus) and perennial grass (Nassella pulchra) were used in donor/receiver pair combinations as were B. hordeaceus and blue oak (Quercus douglasii) seedlings. Net transfers of 15N per gram of shoot tissue favored the annual grass over perennial grass at the flowering stage, and favored oak seedlings over the annual grass during vegetative and flowering stages. Net transfer of rubidium per gram of shoot favored the annual grass over either perennial for all three experiments. 15N and rubidium movement did not appear coupled and gross mass transfers reflected biomass increases.