OOS 21

A Path Forward for Improved Representation of Fine Roots in Large-Scale Models: Linking Models, Data, and Experiments

From coastal wetlands to mountain tops, plant roots serve as a bridge connecting the soil environment to the aboveground ecosystem. Ephemeral roots with a narrow diameter (“fine” roots) are responsible for most plant nutrient and water uptake, contribute organic carbon throughout the soil profile in the form of labile root exudates and decomposing root material, and strongly influence ecosystem CO2 and CH4 fluxes through respiration, rhizosphere oxygenation, and passive transport. Global terrestrial biosphere models are used to represent ecosystem processes and functions, and their feedbacks to the atmosphere, across the diverse biomes of Earth. Fine roots are poorly represented in large-scale models, meaning a key component of ecosystem dynamics is missing. Reasons for the overly-simplistic representation of roots include poor empirical understanding (and therefore representation) of important processes, limited communication among empiricists and modelers, and lack of data from ecosystems spanning the globe. Our objective in this session is to develop a path forward to improve the representation of fine roots in terrestrial biosphere models in order to better project responses of terrestrial ecosystems to global change. We will meet this objective by hosting talks that: (1) Assess current and future model representations of roots; (2) Discuss the availability of root data across the globe to inform model processes; (3) Suggest improvements in model process representation through novel insights from root ecologists; and (4) Develop experimental approaches that will fill gaps in our understanding and representation of fine-root processes. Our approach is based on the notion that root ecologists should be proactive advocates for the inclusion of their data in models. The session will begin with a review of the current representation of root form and function in large-scale models, followed by an improved model representation of fine roots based on empirical data. Next, the role of databases in providing comprehensive data on plant roots from a range of ecosystems will be discussed. Following these initial talks will be recommendations from empiricists on key processes to represent in models - from genetically-linked root traits, to above- and belowground linkages, to rhizosphere dynamics. Technological advancements, including links among roots and high-resolution soil microclimate conditions, as well as new experiments, including root responses to environmental change, will be touched on. The last talk will summarize a community consensus on a path forward to improve model representation of fine roots, drawing in part on knowledge gained from a workshop planned for spring, 2014.