OOS 3 - Missing Links in the Root-Soil Organic Matter Continuum

Monday, August 3, 2009: 1:30 PM-5:00 PM
Brazos, Albuquerque Convention Center
Sarah L. O'Brien, Argonne National Laboratory
Colleen M. Iversen, Oak Ridge National Laboratory
Sarah L. O'Brien, Argonne National Laboratory
Soil organic matter (SOM) is the foundation of a sustainable ecosystem but SOM dynamics are fueled by complex processes that span ecological disciplines. Fine plant roots are an important source of organic inputs to the soil because of their short lifespan and intimate association with the soil profile. Plant and microbial responses to global climate change, land use change, and species invasions will affect the amount of root mass stabilized in soil pools. This will have important consequences for nutrient and water dynamics, the soil food webs that fuel ecosystem processes, and atmospheric carbon dioxide levels. However, ecologists currently have a limited understanding of the processes that drive the transformation of root detritus into SOM because there are few studies that explicitly link plant dynamics directly with soil characteristics. Instead, many ecologists focus their efforts at opposite ends of the root-soil continuum. This has lead to a large knowledge gap between the turnover of root populations and the subsequent fate of root-derived carbon and nitrogen in SOM pools.


Our objective in this session is to synthesize disconnected pieces of knowledge from soil- and root-centric studies into an integrated understanding of important belowground ecosystem processes such as soil carbon and nitrogen cycling. This session will feature a diversity of speakers working at the interface between plant roots and the soil ecosystem. Belowground processes are notoriously difficult to study because most measurements dramatically disturb the soil system and belowground processes occur across a range of spatial and temporal scales. New approaches are needed to advance our understanding of the sustainability of vital belowground processes in the 21st century.

Our speakers will address two key questions:
(1) Can we synthesize an overarching framework for understanding the continuum from plant root inputs to long-term SOM pools from current studies?
(2) What new studies or tools are needed to facilitate our understanding of how plant dynamics drive belowground processes such as SOM formation and ecosystem carbon and nitrogen cycling?

We envision that this session will have broad appeal to ecologists interested in belowground processes, as speakers will discuss topics ranging from the effects of root exudation, chemistry, and soil organisms on the transition of roots to SOM, to the influence of soil attributes on the stabilization of root-derived SOM. An ecosystem modeler will synthesize the importance of these processes by placing them in the context of large-scale ecosystem and soil carbon cycling models.

1:30 PM
 Plant species and soil carbon: At the root of the matter
Ann E. Russell, Iowa State University
1:50 PM
 Defining niche space in savannas: A long-awaited resolution for the two-layer hypothesis
Andrew Kulmatiski, University of Alaska Anchorage; Richard J.T. Verweij, University of Cape Town; Edmund February, University of Cape Town; Karen H. Beard, Utah State University
2:10 PM
 Hydraulic redistribution and the fate of root-derived carbon in soil
Zoe G. Cardon, Marine Biological Laboratory; John M. Stark, Utah State University; Patrick M. Herron, Rowland Institute at Harvard
2:30 PM
 Microbial tools for drought survival in a California grassland
Claudia M. Boot, Colorado State University; Sean M. Schaeffer, University of Tennessee, Knoxville; Allen P. Doyle, University of California Santa Barbara; Joshua P. Schimel, University of California, Santa Barbara
2:50 PM
 Metagenomic analysis of microbial community structure in the rhizosphere of maize and soybean under current and future atmospheric CO2 concentrations
David Nelson, University of South Alabama; Isaac KO Cann, University of Illinois at Urbana-Champaign; Roderick I Mackie, University of Illinois at Urbana-Champaign
3:10 PM
3:20 PM
 Transfer of carbon and nitrogen from decomposing roots into different soil organic matter fractions
Colleen M. Iversen, Oak Ridge National Laboratory; Julie D. Jastrow, Argonne National Laboratory; Richard Norby, Oak Ridge National Laboratory
4:40 PM
 Ecosystem models: The use of models as an overarching framework to synthesize knowledge of the root-soil continuum
William J. Parton, Colorado State University; Robin H. Kelly, Colorado State University; Christopher W. Swanston, USDA Forest Service; Paul J. Hanson, Oak Ridge National Laboratory
See more of: Organized Oral Session
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