Collaborative Research: Restricted Plasticity of Canopy Stomatal Conductance: A Conceptual Basis for Simpler Models of Forest Transpiration

0405306 MacKay Our proposed project has significant intellectual merit because it explicitly addresses two key problems facing hydrology. The first problem concerns the opposing views of stomatal control of water fluxes, with one perspective assuming carbon assimilation control, and the other assuming an environmental control. Our conceptual model combines both of these perspectives in a unified mechanistic framework that combines both assimilation and water potential controls on transpiration. The second problem addressed by our conceptual model is the tendency towards favoring complex and often mathematically ill-posed canopy models over simpler, verifiable ones. We explicitly address this fundamental issue in hydrologic modeling by using a novel, object-oriented canopy model that can flexibly adjust its structure and mechanisms to the data it is provided. By adjusting model complexity spatially we will gain deep insights on species plasticity and restrictions thereof across spatial gradients, thus providing a rigorous approach to testing our conceptual model within our study site in northern Wisconsin. The knowledge gained from our proposed research has broad implications for land surface modeling efforts seeking to generate accurate predictions of global change effects on water cycling. By developing our conceptual model we will be able to provide a relatively simple, but transportable and scientifically defensible model. Such models are essential foundations for the creation and implementation of credible state, federal and international policies aimed at mitigating or otherwise adjusting to the consequences of anticipated global change. The educational emphasis of this project is multi-faceted. First, we will seek additional funding and other means of supporting, advising and training an integrated team of undergraduate students from the economically disadvantaged region of Northern Wisconsin, using this project as the principal context for their education in Forest Ecology at UW-Madison. Also, in connection with the NSF Research Collaboration Network project entitled "Chequamegon Ecosystem- Atmosphere Study," for which Mackay is a core project participant, we will hold a nationally advertised workshop on multi-scale canopy flux measurements and modeling. The PIs will continue to recruit and hire minorities and other underrepresented students in our respective fields.