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Approach

Old-field ecosystems were constructed within 12 4-m diameter open-top chambers and 3 open plots. The whole plots are exposed to ambient or elevated [CO2] combined with ambient or elevated temperature. Two levels of soil moisture are maintained as split-plots within the chambers. Measures of response to these environmental changes include above- and below-ground production, community composition, nitrogen mineralization, soil respiration, and mycorrhizal growth and activity.

Site Description

The experiment will be conducted at the Global Change Field Research Facility on the Oak Ridge National Environmental Research Park. The site has power, well water, buildings for housing monitoring equipment, a 12-ton CO2 receiver with an electrical vaporizer, and a CO2 distribution system. The site is adjacent to the Oak Ridge Experiment on CO2 Enrichment of Sweetgum, a DOE-supported FACE experiment. The land was abandoned from agricultural use in 1943 and left fallow until 1964 when a managed fescue field was established (Kelly 1975). Old-fields in the immediate area are dominated by several Panicum species, Andropogon virginicus, Festuca pratensis, Solidago gigantia, and Lonicera japonica and Rhus toxicodendron. Climatic conditions and soil characteristics are available from the FACE project.


Plant community

In preparation for the initiation of treatments in spring, 2003, experimental plots were established during 2002. 15 plots were laid out in a randomized complete block design. A ditchwitch was used to trench around each 4-m diameter plot and through the center of it on a north-south axis. Foam insulation and plastic sheeting was buried to 0.75 m to provide a thermal and moisture barrier. Seedlings of 7 species were grown from seed and planted in the plots in July, 2002, and April, 2003. The species are:
  • ribgrass (Plantago lanceolata L.), a herbaceous, annual C3 dicot [description]
  • broomsedge (Andropogon virginicus L.), a cespitose C4 bunchgrass [description]
  • meadow fescue (Festuca pratense L. syn F. elatior L.), a C3 bunchgrass [description]
  • orchardgrass (Dactylis glomerata L.), a C3 bunchgrass [description]
  • red clover (Trifolium pratense L.) [description]
  • goldenrod (Solidago canadensis), a perennial forb [description]
  • Lespedeza (Lespedeza cuneata), a perennial nitrogen-fixing shrub [description]
plants plants plants

Dactylis in May clover in May met monitoring


Treatments

Treatments began in May, 2003. Air temperature is maintained at ambient or ambient + 3.5 degrees C. CO2 concentration is maintained at ambient or ambient + 300 ppm. Rain shelters exclude ambient precipitation. Water is added manually to maintain two levels of soil water moisture, which is routinely monitored. Treatment assignments are shown here.

Block 2 plots OTC with rain shelter

Project Personnel

Oak Ridge National Laboratory

Richard J. Norby, ORNL Project leader, project management, facility operation
Aimée Classen, decomposition, soil nitrogen dynamics
Joanne Ledford, minirhizotron analysis
Jeff Riggs, instrumentation and control
Emmi Felker-Quinn, technical support, 2006-
Katherine Sides, technical support, 2005-2006
Shiqiang Wan, postdoctoral associate, 2003-2004
Caroline DeVan, technical support, 2004-2005
Carolyn Reilly, technical support, 2002-2004

University of Tennessee

Jake F. Weltzin, UT Project Leader, plant establishment and aboveground measurements
Orla Dermody, postdoctoral associate, ecosystem gas exchange
Cayenne Engel, graduate participant (2002-2004, field manager, 2005-)
Carolyn Reilly, M.S. candidate
Phil Allen, field manager, 2002-2004

Collaborators

Charles T. Garten, Jr., Oak Ridge National Laboratory, nitrogen fixation
R. Michael Miller, Argonne National Laboratory, mycorrhizal assessment



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Last revised: June 25, 2006