(1) partitioning of soil respiration between autotrophic and heterotrophic sources, and quantification of that partitioning seasonally and inter-annually,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.
(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.
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
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.