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Summary
(Adapted from abstract presented at ARS Carbon Storage Workshop,
Baltimore MD, Jan 1999)


Problems: During the past few decades the atmospheric concentration
of CO2 has been increasing at historically unprecedented
rates. Increasing CO2 concentrations will have a direct effect on
plant production and plant communities and indirectly feed back into ... a
number of soil biotic systems that influence long-term ecosystem
characteristics, including aspects of C and. N cycling. The impact of
elevated CO2 on the shortgrass steppe and northern mixed prairieshas
not been addressed.

Approach: Two suites of experiments are being conducted to address
how elevated CO2 affects the ecology and cycling of C and N in
grasslands.- A field, open-top chamber study on shortgrass steppe at
the Central Plains Experimental Range, led by Arvin Mosier
(USDA-ARS,Soil Plant- Nutrient Research Ft. Collins, CO), is
evaluating how a doubling of CO2 concentrations over shortgrass steppe
affects plant production, physiology, soil microbiology and gas
exchange of trace gases (CH4' NO and N2O). In related growth chamber
work, plant physiological, growth, partitioning responses plus C and N
cycling of native grass/soils exposed to various combinations ofCO2,
defoliation treatments, soil water availability and temperature are
being evaluated and modeled.

Findings: Results from the first year of the open-top chamber study
revealed the following. A doubling ofCO2 from 350 to 700 micromol
mol-l enhanced seasonal aboveground production of both C3 and C4
grasses by 30%, due to more favorable water relations and
higherphotosynthesis. Trace gas fluxes were not significantly
different from soils under ambient atmosphere -compared to those under
double CO2 atmosphere. Soil/plant respiration and N2O emissions tended
to be lower under double CO2. During the winter NOx fluxes tended to
be into the soil whilegrowing season fluxes were always positive with
growing season NO/N2O ratios averaging between7 and 10. Daily CENTURY
Model results suggest that the most important belowground effect of
doubling CO2 is to increase root production and soil water content
during the growing season. In growth chamber studies, the stimulation
of growth and partitioning of that new growthto belowground organs
varied between a cool- and warm-season grass as well as among
developmental growth stages, and was successfully modeled by an
approach that utilized the balanced growth concept. As with the field
study, CO2-enhanced growth responses were observed for both C3 and C4
grasses.

Future Plans: The open-top chamber study will continue for three more
years, and will incorporate new studies, including 13C labeling
studies to more accurately track belowground C inputs and cycling,
soil soluble C studies, and a project to evaluate interactive effects
ofCO2 and soil type on plant responses. A second growth chamber
project was just completed in which cylinders containing soil and
associated northern mixed prairie vegetation weresubjected to variable
CO2, N and defoliation regimes. Laboratory analyses for soluble
carbohydrates, and isotopes of C and N will be completed over the
winter on plant/soil samples obtained from this study, and the
treatments will be evaluated for affects on plant physiological
attributes, including biomass partitioning to belowground organs,
productivity, as well as soil C and N cycling.

Geographic Coverage Spatial coordinates   

N: 42.0

S: 40.0

E: -104.0

W: -105.0

Data Set Citation

Dataset Creator: J.A. Morgan, A.R. Mosier, D.R. LeCain, W.J. Parton, H.W. Hunt, J.J.Read, D.G. Mi Dataset Title: Impacts of CO2 Enrichment on C Sequestration in Native Grasslands Dataset Release Date: 1999 Dataset Release Place: Ft. Collins, Colorado Dataset Publisher: Rangeland Resources Research Unit, USDA-ARS

Temporal Coverage

Start Date: 1998-01-01

Location Keywords

CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > COLORADO

Science Keywords

AGRICULTURE > AGRICULTURAL PLANT SCIENCE > CROPPING SYSTEMS AGRICULTURE > SOILS > ORGANIC MATTER AGRICULTURE > SOILS > SOIL CHEMISTRY AGRICULTURE > SOILS > SOIL FERTILITY AGRICULTURE > SOILS > SOIL RESPIRATION ATMOSPHERE > ATMOSPHERIC CHEMISTRY > TRACE GASES/TRACE SPECIES BIOSPHERE > ECOLOGICAL DYNAMICS > ECOSYSTEM FUNCTIONS > BIOGEOCHEMICAL CYCLES BIOSPHERE > ECOLOGICAL DYNAMICS > ECOSYSTEM FUNCTIONS > BIOMASS DYNAMICS BIOSPHERE > ECOLOGICAL DYNAMICS > ECOSYSTEM FUNCTIONS > DECOMPOSITION BIOSPHERE > ECOLOGICAL DYNAMICS > ECOSYSTEM FUNCTIONS > PHOTOSYNTHESIS BIOSPHERE > VEGETATION > BIOMASS > ABOVEGROUND BIOSPHERE > VEGETATION > BIOMASS > BELOWGROUND

ISO Topic Category

FARMING GEOSCIENTIFIC INFORMATION CLIMATOLOGY/METEOROLOGY/ATMOSPHERE BIOTA

Platform

GROUND-BASED OBSERVATIONS

Quality
study not complete

Access Constraints
no access until study is complete

Use Constraints
none

Ancillary Keywords

C3 GRASS C4 GRASS CARBON FLUX CARBON SEQUESTRATION CARBON SINK CARBON STORAGE CENTRAL PLAINS EXPERIMENTAL RAN CENTURY MODEL CPER ECOSYSTEM MODELING ELEVATED CARBON NORTHERN MIXED GRASS PRAIRIE SHORTGRASS STEPPE

Data Set Progress

IN WORK

Originating Center

USDA-ARS

Data Center

Soil, Plant, and Nutrients Research Unit, Agricultural Research Service, U. S. Department of Agriculture Data Center URL: http://spnr.ars.usda.gov/ Data Center Personnel Name: ARVIN MOSIER Phone: 970-490-8250 Fax: 970-490-8213 Email: amosier at lamar.colostate.edu Contact Address: USDA Agricultural Research Service Soil, Plant, and Nutrients Research Unit Federal Building P.O. Box E City: Fort Collins Province or State: CO Postal Code: 80522 Country: USA

Personnel

JON D. HANSON Role: INVESTIGATOR Phone: (701) 667-3010 Fax: (701) 667-3054 Email: jon at mandan.ars.usda.gov Contact Address: USDA-ARS Northern Great Plains Research Laboratory Highway 6 South City: Mandan Province or State: ND Postal Code: 58554 Country: USA RICHARD H. HART Role: INVESTIGATOR Phone: (307) 772-2433 Fax: (307) 637-6124 Email: rhart at lamar.colostate.edu Contact Address: USDA Agricultural Research Service High Plains Grasslands Research Station 8408 Hildreth Road City: Cheyenne Province or State: WY Postal Code: 82009 Country: USA H. WILLIAM HUNT Role: INVESTIGATOR Phone: (970) 491-1985 Fax: (970) 491-1965 Email: billh at nrel.colostate.edu Contact Address: Natural Resources Ecology Laboratory Natural and Environmental Sciences Bldg., B244 Colorado State University City: Ft. Collins Province or State: CO Postal Code: 80523 Country: USA GORDON L. HUTCHINSON Role: INVESTIGATOR Phone: (970) 490-8200 Fax: (970) 490-8213 Email: glhutch at lamar.colostate.edu Contact Address: USDA-ARS Soil, Plant, Nutrient Research Unit Federal Building 301 S. Howes, Room 407 P.O. Box E City: Fort Collins Province or State: CO Postal Code: 80522 Country: USA W. G. KNIGHT Role: INVESTIGATOR DANIEL R. LECAIN Role: INVESTIGATOR Phone: (970) 498-4217 Fax: (970) 482-2909 Email: lecain at lamar.colostate.edu Contact Address: Rangeland Resources Research Unit, USDA-ARS CROPS RESEARCH LAB 1701 Center Ave City: Fort Collins Province or State: CO Postal Code: 80526-2083 Country: USA DANIEL G. MILCHUNAS Role: INVESTIGATOR Phone: (970) 491-6691 Fax: (970) 491-2156 Email: dannym at cnr.colostate.edu Contact Address: Department of Rangeland Ecosystem Science Colorado State University City: Ft. Collins Province or State: CO Postal Code: 80523 Country: USA JACK A. MORGAN Role: INVESTIGATOR Phone: (970) 498-8216 Fax: (970) 482-2909 Email: morgan at lamar.colostate.edu Contact Address: USDA-ARS Rangeland Resources Research Unit CROPS RESEARCH LAB 1701 Center Ave City: Fort Collins Province or State: CO Postal Code: 80526 Country: USA ARVIN MOSIER Role: INVESTIGATOR Role: TECHNICAL CONTACT Phone: 970-490-8250 Fax: 970-490-8213 Email: amosier at lamar.colostate.edu Contact Address: USDA Agricultural Research Service Soil, Plant, and Nutrients Research Unit Federal Building P.O. Box E City: Fort Collins Province or State: CO Postal Code: 80522 Country: USA DENNIS S. OJIMA Role: INVESTIGATOR Phone: (970) 491-1976 Fax: (970) 491-1965 Email: dennis at nrel.colostate.edu Contact Address: Natural Resources Ecology Laboratory Natural and Environmental Sciences Bldg., B229 Colorado State University City: Ft. Collins Province or State: CO Postal Code: 80523 Country: USA WILLIAM J. PARTON Role: INVESTIGATOR Phone: (970) 491-1987 Fax: (970) 491-1965 Email: billp at nrel.colostate.edu Contact Address: Natural Resources Ecology Laboratory Natural and Environmental Sciences Bldg., B233 Colorado State University City: Ft. Collins Province or State: CO Postal Code: 80523 Country: USA J. J. READ Role: INVESTIGATOR J. D. REEDER Role: INVESTIGATOR Phone: (970) 498-4236 Fax: (970) 482-2909 Email: jdreeder at lamar.colostate.edu Contact Address: USDA-ARS Rangeland Resources Research Unit CROPS RESEARCH LAB 1701 Center Ave City: Fort Collins Province or State: CO Postal Code: 80526-2083 Country: USA GERALD E. SCHUMAN Role: INVESTIGATOR Phone: (307) 772-2433 Fax: (307) 637-6124 Email: gschuman at lamar.colostate.edu Contact Address: High Plains Grasslands Research Station USDA Agricultural Research Service 8408 Hildreth Road City: Cheyenne Province or State: WY Postal Code: 82009 Country: USA R. HOWARD SKINNER Role: INVESTIGATOR Phone: (970) 490-8322 Fax: (970) 490-8310 Email: skinner at gpsr.colostate.edu Contact Address: Great Plains Systems Research Unit USDA-ARS P.O. Box E 301 South Howes St. City: FT. COLLINS Province or State: CO Postal Code: 80522 Country: USA TYLER B. STEVENS Role: DIF AUTHOR Phone: (301) 614-6898 Fax: 301-614-5268 Email: Tyler.B.Stevens at nasa.gov Contact Address: NASA Goddard Space Flight Center Global Change Master Directory City: Greenbelt Province or State: MD Postal Code: 20771 Country: USA

Publications/References
Hunt, H.W., J.A. Morgan, and J.J. Read. 1998. Simulating growth and
root-shoot partitioning in prairie grasses under elevated atmospheric
CO2 and water stress. Ann. of Botany81:489-501.

Morgan, J.A., D.R. LeCain, A.R. Mosier, D.G. Milchunas. 1998. Carbon
dioxide enrichment on the shortgrass steppe in Colorado: Physiological
responses of dominant C3 and ... C4 grasses. Proceedings of the GCTE-LUCC
Earth's Changing Land Conference, Barcelona, Spain, March, 1998.

Morgan, J.A., D.R. LeCain, A.R. Mosier, D.G. Milchunas, W.J. Parton,
and D. Ojima. 1998. Carbon dioxide enrichment enhances
photosynthesis, water relations and growth in C3 and C4 shortgrass
steppe grasses. ESA Abstracts, p 196.

Morgan, J.A. 1998. Global Warming Under the Scope: What does global
climate change mean for western rangelands? Western Beef Producer.
Mid-February, March and Mid-March issues.

Morgan, J.A., D.R. LeCain, J.J. Read, H.W. Hunt and
W.G. Knight. 1998. Photosynthetic pathway and ontogeny affect water
relations and the impact ofCO2 on Bouteloua gracilis (C4) and
Pascopyrum smithii (C3). Oecologia 114. 483-493.

Mosier, A.R., J.A. Morgan, W.J. Parton, D.G. Milchunas,
D.S. Ojima. 1998. Tracegas exchange in the Colorado Shortgrass Steppe
under elevated CO2. Agronomy Abstracts, p. 210.

Parton, W.J., M. Coughenour, A.R. Mosier, D.S. Ojima. 1998. Simu1ated
impact of2 X CO2 levels on Great Plains grassland soils. Agronomy
Abstracts, p. 306.

Polley, H. W., J.A. Morgan, M. Stafford-Smith and
B. Campbell. 1999. Rangelandsin a Changing World, IN Crop Ecosystem
Responses to Global Climate Change, CAB International, UK. (in press )

Skinner, R.H., J.A. Morgan and J.D. Hanson. 1999. Carbon and nitrogen
reserve remobilization following defoliation: Nitrogen and elevated
CO2 effects. Crop Science (in press) -

Creation and Review Dates

Last DIF Revision Date: 1999-09-09

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