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Oak Ridge National Environmental Research Park

Research Park Notes
Issue 9, March 20, 2001

Welcome to Research Park Notes! Look for tidbits of information on National Environmental Research Park activities, observations, and users every couple of weeks. To provide newsletter input, request additional information, make comments, or add/delete mailing list names, contact the Oak Ridge National Laboratory Area Manager, Pat Parr.


Forest Water Use Studied on Walker Branch Watershed - Stan Wullschleger, Environmental Sciences Division, ORNL

Forests, like all terrestrial ecosystems, use water in amounts that are determined by climate, length of growing season, canopy leaf area, species composition, and soils. The total amount of water used by an ecosystem, however, is not the sole result of any one process, but instead represents the sum of several components including plant transpiration, soil water evaporation, loss of water to deep soils, surface run-off, and canopy interception. Collectively these processes are termed evapotranspiration, or simply ET. Unfortunately, although many studies have quantified ET for different landscapes, no study has quantified the magnitude of ET and its components across multiple spatial scales ranging from single plants, soil samples and soil profiles, the atmospheric surface layer, and entire watersheds. That is, not until now. In a unique multi-year monitoring campaign taking place on Walker Branch Watershed, a collaborative effort between Oak Ridge National Laboratory’s Environmental Sciences Division (ORNL/ESD) and the National Oceanic and Atmospheric Administration’s Atmospheric Turbulence Diffusion Division (NOAA/ATDD) scientists are measuring rates of ET and unraveling its component processes using a combination of unique methodologies. This multi-disciplinary team composed of Paul Hanson, Pat Mulholland, and Stan Wullschleger from ESD and Kell Wilson and Dennis Baldocchi from ATDD have brought together four independent techniques to quantify rates of forest water use. These include a range of automated technologies for measuring soil water content, sap velocity, eddy covariance, and long-term records of catchment water yield from V-notched weirs installed on both the East and West Forks drainages of the Walker Branch Watershed in the Oak Ridge National Environmental Research Park.

According to a recent article featured in the journal Agricultural and Forest Meteorology, annual estimates of ET for a mixed deciduous forest on Walker Branch Watershed were similar for the eddy covariance and catchment water budget techniques. Estimates of ET averaged over a 5-year period (1995-1999) were 571±16 mm (eddy covariance) and 582±28 mm (catchment water budget) per year. Quantitative similarities between sap velocity and eddy covariance were observed on a daily basis, and sap velocity estimates of transpiration scaled to the stand were about 50% of annual ET as estimated from the eddy covariance and catchment methods. There was caution, however, that estimates of transpiration derived from sap velocity measurements may be too low, that is unless evaporation of canopy-interception was especially large. Species diversity and abundance of ring-porous trees (oaks) across the watershed may explain the difficulties associated with extrapolating individual tree estimates of sap velocity to the spatial scales represented by the eddy covariance and catchment water yield methods.

Thanks to partial support provided by DOE, NOAA, and NASA, these studies are continuing and hopefully will provide useful information to ecologists, forest hydrologists, modelers, and others that are interested in the water balance of temperate forest ecosystems. Such measurement capabilities and collaboration among scientists will provide a foundation for future activities, especially those related to a pending multi-agency initiative aimed at better understanding the global water cycle. For a completed description of the collaborative research effort, readers are directed to the following reference:

Wilson, K. B., P. J. Hanson, P. J. Mulholland, D. D. Baldocchi, and S. D. Wullschleger. 2001. A comparison of methods for determining forest evapotranspiration and its components: sap-flow, soil water budget, eddy covariance, and catchment water balance. Agricultural and Forest Meteorology 106, 153-168.

For more information about research on Walker Branch Watershed, check out For information about the Atmospheric Turbulence Diffusion Division, see


We’ve had many inquiries about public walks on the reservation this spring. Yes, we are hoping to offer them again. Keep an eye on “Park Notes” for updated information. And, we’re always looking for interested volunteers to lead walks!


Pat Parr briefed Department of Energy (DOE) employees and contractors from Washington and other DOE sites on Oak Ridge National Laboratory Land and Facility Planning at the DOE session of the Federal Planning Division workshop March 8 in New Orleans. The discussion included updates to the 2000 ORNL Land and Facility Plan, particularly use of the land area for DOE mission research and facilities revitalization.


Rustad, L. E., J. L. Campbell, G. M. Marion, R. J. Norby, M. J. Mitchell, A. E. Hartley, J. H. C. Cornelissen, and J. Gurevitch. 2001. GCTE-NEWSA meta-analysis of the response of soil respiration, net nitrogen mineralization, and aboveground plant growth to experimental ecosystem warming. Oecologia 126 (2001) 4, 543-562, DOI 10.1007/s004420000544. For more information, see

Bob Cushman of CDIAC prepared the Numeric Data Package, "Carbon Flux to the Atmosphere From Land-use Changes1850 to 1990" (NDP-050/R1), contributed by Richard Houghton and Joseph Hackler of the Woods Hole Research Center. This updated NDP replaces the version published by CDIAC in 1995 and includes the data corresponding to Houghton's 1999 paper, "The annual net flux of carbon to the atmosphere from changes in land use 1850-1990," in the journal Tellus (volume 51B, pages 298-313). For more information, see


April 3, 2001 – Tennessee Chapter, The American Chestnut Foundation, Village Green Clubhouse, Knoxville, Tennessee, 6:30 p.m. More info:

April 4-7, 2001 – Association of Southeastern Biologists Annual Meeting in New Orleans, Louisiana. More info:

April 25-29, 2001 – The 16th Annual Symposium of the U.S. Regional Chapter of the International Association of Landscape Ecology (US-IALE), Arizona State University, Tempe, Arizona. More info:

April 30 - May 2, 2001 – "Water Quality Monitoring and Modeling," American Water Resources Association, Annual Spring Specialty Conference, The Menger Hotel, San Antonio, Texas. More info:

May 2-3, 2001 – SAMAB Spring Planning Meeting, The North Carolina Arboretum, Asheville, North Carolina. More info:

May 10, 2001 – Tennessee Chapter, The American Chestnut Foundation, Village Green Clubhouse, Knoxville, Tennessee, 6:30 p.m. More info:

May 29 - June 2, 2001 – American Geophysical Union (AGU) meeting in Boston. Abstracts are due March 8. In addition to its strength in subsurface science and geochemistry, AGU is continuing to expand its focus on biogeoscience and watershed hydrology. More info:

May 31 - June 1, 2001 – The 3rd Annual Governors Summit on Mountain Air Quality, Park Vista Hotel in Gatlinburg, Tennessee.

June 27-29, 2001 – "Decision Support Systems for Water Resources Management," AWRA/UCOWR Summer Specialty Conference, Snowbird Resort, Snowbird, Utah. More info: Contact AWRA Headquarters [(540) 687-8390] or

August 5-8, 2001 – "Globalization and Water Management--The Changing Value of Water," AWRA/University of Dundee International Specialty Conference, University of Dundee, Dundee, Scotland. More info: Contact AWRA Headquarters [(540) 687-8390] or

August 5-10, 2001 – The 86th Annual Meeting of the Ecological Society of America, Madison, Wisconsin. More info:

October 3-6, 2001 – Natural Areas Association Annual Conference at Cape Canaveral, Florida, on “Searching for a Natural Balance.” More info:

November 12-15, 2001 – Annual Water Resources Conference, Hyatt Regency Albuquerque, Albuquerque, New Mexico. More info: Contact AWRA Headquarters [(540) 687-8390] or

November 26-28, 2001 – Southern Forest Science Conference, Contributions of Forest Research to Sustainable Forestry, Atlanta, Georgia. More info: or call (828) 257-4302.

The Oak Ridge National Environmental Research Park was designated by the Department of Energy in 1980 and is one of a network of seven National Environmental Research Parks. It is an Oak Ridge National Laboratory User Facility. The Oak Ridge National Environmental Research Park was designated an international biosphere reserve in 1989. It is also a unit member of the Southern Appalachian Biosphere Reserve and part of the Southern Appalachian Man and the Biosphere (SAMAB) Cooperative. More information on the Oak Ridge National Environmental Research Park can be found on the website at:

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Last Updated: May 4, 2001
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