 |
| The
flux of carbon dioxide is measured
between the atmosphere above the
plant canopy on the trees of a
forest ecosystem. In the vast
majority of AmeriFlux sites the
flux is into the trees resulting
in the forest becoming a significant
sink for excess CO2 from the atmosphere.
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Major changes are occurring in the
chemical composition of the atmosphere,
most notably an increase in carbon
dioxide (CO2) concentration. A fuller
understanding of the global carbon
cycle is needed so that future changes
can be predicted and policies can
be developed on energy use. Roughly
half of the CO2 released by human
activities remains in the atmosphere;
scientists do not know whether the
missing half is sequestered in the
deep oceans, soils, or plant biomass.
Recently, some clues have been found.
Over the past 10 years, university
researchers supported by the Office
of Science have discovered that net
carbon sequestration by forests along
a north-south climate gradient, ranging
from Canada to the southeastern United
States, increases with rising temperature.
This discovery was made using the
AmeriFlux facilities, a network of
approximately 25 research sites in
a large variety of ecosystems in North,
Central, and South America. At each
site, continuous measurements are
made of the turbulent exchange of
CO2, water vapor, and energy between
the atmosphere and terrestrial biosphere.
Scientific Impact:
AmeriFlux data will help scientists
understand why the sequestration of
carbon varies among different types
of terrestrial ecosystems, and how
their capacity to sequester carbon
might change in response to human-induced
and natural changes in climatic conditions.
The data also will be used to test
elements of global climate and ecosystem
models.
Social Impact: This
work will help society make wise decisions
about land use and land management,
such as whether forests will be protected
and managed to remain an important
net sink for atmospheric CO2 or are
converted to other land uses that
are a smaller net sink or a net source
of CO2. Possible adverse effects of
elevated CO2 levels include global
warming.
Reference: Baldocchi,
D., R. Valentini, S. Running, W. Oechel,
and R. Dahlman. "Strategies for measuring
and modelling carbon dioxide and water
vapour fluxes over terrestrial ecosystems,"
Global Change Biology, 2:159,
1996.
Law, B.E., A.H. Goldstein, P.M. Anthoni,
M.H. Unsworth, J.A. Panek, M.R. Bauer,
J.M. Fracheboud, N. Hultman. "CO2
and water vapor exchange by young
and old ponderosa pine ecosystems
during a drought year," Tree Physiology,
21:299, 2001.
Wofsy, S.C., M.L. Goulden, J.W. Munger,
S.M. Fan, P.S. Bakwin, B.C. Daube,
S.L. Bassow, and F.A. Bazzaz. "Net
exchange of co2 in a midlatitude forest,"
Science, 260:1314, 1993.
URL:
http://cdiac.esd.ornl.gov/programs/ameriflux/
Technical Contact:
Dr. Roger Dahlman, Environmental Sciences
Division, Office of Biological and
Environmental Research
Press Contact: Jeff
Sherwood, DOE Office of Public Affairs,
202-586-5806
SC-Funding Office:
Office of Biological and Environmental
Research |
