PARENT SESSION
Thursday, August 10, 1:30-5:00 pm
Symposium 20 - Multiple resource limitation in terrestrial and aquatic ecosystems
Cotton Row, Mezzanine Level, Cook Convention Center
Organized by: AC Finzi (afinzi@bu.edu) and LO Hedin
This symposium will bring together an acclaimed group of scientists working on issues of multiple resource limitation in very different systems (terrestrial, aquatic, marine) with the goal of stimulating interest in multiple resource limitation to ecosystem function in the biogeosciences.
Resource optimization and the Multiple Element Limitation (MEL) model.
Rastetter, Edward*,1, Shaver, Gaius1, Ågren, Göran2, 1 The Ecosystems Center, Woods Hole, MA2 Swedish University of Agricultural Research, Uppsala, Sweden
ABSTRACT- The resource optimization paradigm and the related concept of ecological stoichiometry have gradually emerged in the literature over the past fifty years. Ecological stoichiometry is the study of how the ratios of elements in living organisms place constraints on ecological processes like plant growth, trophic transfers of mass and energy, and the decomposition of organic matter. Resource optimization theory predicts how organisms should allocate their internal assets (biomass, proteins, carbohydrate...) to acquire resources from the environment (C, N, water, light...) in the face of these constraints. There are two important predictions of resource optimization theory. First, organisms should reallocate their internal assets toward a condition where the instantaneous rate of uptake is limited equally for all resources. This short-term limitation on uptake kinetics of all resources should occur even if the long-term limitation on growth and biomass accumulation is by the supply rate of only a single resource. Second, if there is more than one resource able to fill a requirement (i.e., substitutable resources), then allocation should be toward the resource that requires the fewest assets to acquire. If assets were distributed otherwise, then too many assets would be expended toward acquiring non-limiting or overly expensive resources. Reallocation of those assets toward limiting or less expensive resources would therefore increase production, which should confer a competitive advantage on ecological time scales and a selective advantage on evolutionary time scales. Changes in resource availability and in metabolic requirements through time complicate this picture, but the overall concept still applies: Organisms should constantly adjust the distribution of their internal assets to approach a more balanced and more efficient pattern of resource uptake from the environment. We review this theory, our latest mathematical formulation of it, and the major conclusions we derived from the model.
Key words: resource optimization paradigm, multiple resource limitation, ecosystem biogeochemistry