Friday, August 10, 2007: 8:00 AM-11:30 AM
C3&4, San Jose McEnery Convention Center
OOS 49 - Controls over nitrogen fixation: A global perspective
Biological nitrogen (N) fixation, a conversion of inert atmospheric N to a biologically available form, is a key driver of ecosystem function. N fixation is also a mediator of system responses to disturbance, ranging from land clearance to increasing atmospheric CO2, and the process may represent the only truly sustainable way to deliver new N to ecosystems. Despite its importance and the fact that N fixation has been identified as a vital area for research in ecosystem studies for several decades, N fixation remains poorly understood, and the understanding we do have often seems paradoxical. In addition, a scarcity of measurements, particularly outside of temperate systems, sometimes mires discussions in speculation. However, studies attempting to elucidate N fixation controls are now underway in many parts of the globe. This session will highlight new directions in N fixation research and will offer a venue for information integration. We hope not only to ask how N fixation inputs vary among ecosystems, but also to investigate what factors appear to drive variations both within and across systems. Talks will address symbiotic, associative, and free-living N fixation using a range of approaches (molecular, isotopic, computational) and will ask: What are the significant N fixation inputs in these systems? What are the key factors controlling fixation? How are N fixation rates expected to change as ecosystems respond to local and global environmental change? We hope that this session will offer insight into N fixation rates and controls for both scientists interested in N fixation and land managers considering N fixation for ecosystem maintenance and remediation.
Organizer:Alex R. Barron, Carleton College
Co-organizer:Sasha C. Reed, University of Colorado, Boulder
Moderator:Sasha C. Reed, University of Colorado, Boulder
8:00 AMOOS 49-1Spatial variation and effects of nitrogen deposition on biological nitrogen fixation and nitrogen pools in two tropical forest types
Daniela F. Cusack, University of California - Berkeley, Whendee Silver, University of California - Berkeley, William H. McDowell, University of New Hampshire
8:20 AMOOS 49-2High rates of total nitrogen fixation in a tropical dry forest
Louis Santiago, University of California, Riverside
8:40 AMOOS 49-3Molybdenum limitation of tropical nitrogen fixation: A widespread phenomenon?
Alexander R. Barron, Carleton College, Anne Kraepiel, Princeton University, Lars Hedin, Princeton University
9:00 AMOOS 49-4Species controls over free-living nitrogen fixation in a tropical rain forest
Sasha C. Reed, University of Colorado, Boulder, Cory C. Cleveland, University of Colorado, Boulder, Alan R. Townsend, University of Colorado, Boulder
9:20 AMOOS 49-5Fixing the nitrogen budget in oligotrophic arctic lakes: Reassessing the importance of benthic and pelagic nitrogen fixation
Gretchen M. Gettel, University of New Hampshire, Anne E. Giblin, Marine Biological Laboratory, Robert W. Howarth, Cornell University, Lyndon Q. Valicenti, Columbia University
9:40 AM Break
9:50 AMOOS 49-6Nitrogen fixation in the open ocean: Small cells, big deal
Joseph P. Montoya, Georgia Institute of Technology, Ian Hewson, UC Santa Cruz, Jonathan P Zehr, UC Santa Cruz
10:10 AMOOS 49-7Adaptive nitrogen fixation strategies with realistic tradeoffs allow persistent N limitation and N richness
Duncan N. L. Menge, Princeton University, Simon Levin, Princeton University, Lars Hedin, Princeton University
10:30 AMOOS 49-8Diazotrophs are everywhere: Quantifying nitrogen inputs from unexpected sources
Jayne Belnap, US Geological Survey
10:50 AMOOS 49-9Responses of nitrogen fixation to elevated CO2
Bruce A. Hungate, Northern Arizona University

See more of Organized Oral Session

See more of The ESA/SER Joint Meeting (August 5 -- August 10, 2007)