Enriched Background Isotope Study (EBIS)
Application of an Ecosystem-scale 14C Tracer to
Soil-Carbon-Cycle Studies
Project Abstract
A unique, large release of radiocarbon occurred near the Oak Ridge
Reservation
(ORR), Oak Ridge, TN in July/August 1999. Measurements of 14C
in tree ring
cellulose throughout the ORR area demonstrate that the 1999 release was
unprecedented in its uptake by vegetation. We are taking
advantage
of the whole-ecosystem isotopic label generated by this release to
address
five outstanding issues in the terrestrial carbon cycle:
(1)
partitioning of soil respiration between autotrophic and heterotrophic
sources, and quantification of that partitioning seasonally and
inter-annually,
(2) partitioning of heterotrophic respiration sources between
above-ground
litter decomposition and below-ground root detritus decomposition,
(3) identification of pathways leading from leaf and root detritus
to long-term stabilization of soil organic matter, including the role
of
soil fauna,
(4) the role of dissolved organic carbon (DOC) transport in
distributing
carbon within the soil profile, and
(5) the longevity and turnover time of fine roots.
The first four issues are being addressed through a reciprocal litter
transplant
experiment set up at four sites on the ORR encompassing two soil types
and two levels of 14C exposure in 1999. The fifth issue,
longevity and
turnover of fine roots, is being addressed by tracing the radiocarbon
label
through the fine root pool over time. With a combination of incubation,
soil surface chamber and soil CO2 profiles, and continuous
measurements
of soil temperature and moisture controls, we are tracking changes in
soil
respiration partitioning over several years. The nature and
source
of organic matter pools that reside in soils for years to decades are
being
tracked with differently labeled root and surface litter, and
experiments
to exclude soil fauna have been initiated to elucidate their role in
vertical
transport. Periodic sampling of soils and soil solutions and the
use of inert tracers, allow us to investigate the chemical nature and
form
of DOC and its transport in surface soil horizons. Results from these
field
observations will be used to parameterize and refine existing carbon
dynamics
models. Such models will then be used to quantitatively address
the
long-term fate of ecosystem carbon inputs and the potential for
ecosystem
carbon sequestration.
Click here to
download the original proposal text in pdf format (minus budget pages,
vitae, and statements of support).
EBIS Posters in PDF Format
Hanson, P.J. et al. (2002) Enriched background
isotope
study (EBIS): application of an ecosystem-scale 14C tracer to
soil-carbon-cycle
studies. Annual Meeting of the Soil Science Society of America,
Indianapolis,
Indiana, 10-14 November 2003.
Cisneros-Dozal1 LM et al. (2003) Quantifying
Sources of Soil Respiration Using 14C-Enriched Leaf Litter and Roots in
a Temperate Forest. National Science Foundation North American
Carbon
Program Joint PI Meeting (NACP '03), Arlington, Virginia, 12-14 May
2003.
Jastrow JD et al. (2003) Incorporation of a
whole ecosystem radiocarbon label into unprotected and protected soil
carbon
pools. Soil Ecology Society Ninth Biannual International
Conference,
Palm Springs, CA. 11-14 May 2003.
Swanston C., et al. (2003) Radiocarbon
flux
into labile and stable soil organic matter pools in the Enriched
Background
Isotope Study (EBIS) 18th International Radiocarbon Conference,
Wellington,
New Zealand, from 1?5 of September 2003.
Torn M, et al. (2003) A Forest 14C Pulse-Label
Study of Root Turnover and Microbial Dynamics (EBIS). 18th
International
Radiocarbon Conference, Wellington, New Zealand, from 1?5 September
2003.
Hanson, P.J. et al. (2003) Enriched
background
isotope study (EBIS): application of an ecosystem-scale 14C tracer to
soil-carbon-cycle
studies (Updated Poster). TCP Science Team Meeting, Boulder,
Colorado,
16-17 October, 2003.
Joslin JD et al. (2003) Fate of fine root
carbon
in a carbon-14-labeled forest ecosystem. Annual Meeting, Soil
Science Society of America, Denver, Colorado, 2-6 November 2003.
Todd, D.E. et al. (2003) Transport and
sequestration
of organic C in contrasting soils amended with C-14 enriched leaf litter.
Annual Meeting of the Soil Science Society of America, Denver,
Colorado,
2-6 November 2003.
Send general questions or comments on this page to:
Paul J. Hanson (hansonpj@ornl.gov)
EBIS Project Coordinator
Environmental Sciences Division
Oak Ridge National Laboratory
Bethel Valley Road, Building 1062
Oak Ridge, TN 37831-6422 USA