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[GCTE Contact: Rob Jackson, jackson@duke.edu, http://www.biology.duke.edu/jackson]
Introduction
Roots play a central role in nutrient and water dynamics, both in providing a mechanism for temporal separation of resource capture/loss at the ecosystem level and in structuring the competitive interactions among ecosystem components. The purpose of this task is to understand the importance of root distributions, and belowground processes in general, on ecosystem carbon and water fluxes. An accompanying goal is to improve the representation of belowground processes in global models. Both of these will be examined in the context of such drivers as elevated CO2 , nutrient deposition, and land-use change (particularly changes in plant life forms). This task consists of three components: literature syntheses, field projects, and modeling integration. The goals of this task are also important to the Biosphere Aspects of the Hydrological Cycle (BAHC) project. Several joint GCTE-BAHC projects and meetings are already planned (se below). In addition, a joint project with GCTE and DIS (Data Information Systems) is proposed to generate global rooting maps. Incorporating rooting depth into a General Circulation Model (GCM) will also be done jointly with GCTE Activity 1.4.
Objectives
• To predict the effects of global change on root phenology, mycorrhizae, and below-ground primary production
• To understand how altered plant functional types, atmospheric CO2, or nutrient deposition affect rooting depth and the distribution of microbial communities in the soil>
• To incorporate root distributions into GCMs and to examine the effect of changes in plant life forms on carbon and water fluxes
• To understand the importance of deep roots in structuring plant communities
Implementation
Literature syntheses will be an important component of early implementation. These syntheses will include the analysis of root and mycorrhizal attributes globally and their relationship to environmental variables (e.g., precipitation, soil texture). See http://www.biology.duke.edu/jackson/roots.htm for early results. These data will be used to improve the representation of belowground processes in ecosystem and global models, and for understanding the controls of belowground NPP. Field campaigns will also be initiated along IGBP transects to examine the role of altered root distributions on carbon and water fluxes.
Proposed Timetable
• 1998 GCTE-DIS Workshop - to Generate a Functional Soil Depth
• 1999 GCTE-BAHC-GEWEX Workshop - Root Distribution and Water Fluxes, Paris
• 1999 GCTE activity 1.1/1.3 Workshop on fine root dynamics and primary productivity