The Enriched Background Isotope Study (EBIS)

Hanson, Paul J. ; Trumbore, Susan ; Swanston, Chris ; Torn, Margaret ; Jastrow, Julie ; Parton, William A. ; Post, Wilfred M. ; Fröberg, Mats J. ; Hainsworth, Laura J. ; Kleber, Markus ; Kramer, Christiane ; Matamala-Paradeda, Roser ; Jr., Charles T. Garten

University of California, Irvine, CA 92697

关键词: Transplants;    Plants;    Respiration;    Ebis, Radiocarbon, Accelerator Mass Spectrometry, Soil Carbon, Carbon Sequestration;    Stabilization;   

DOI  :  10.2172/899557
RP-ID  :  DOE/FG/63910-1
RP-ID  :  FG02-04ER63910
RP-ID  :  899557

美国|英语

来源: UNT Digital Library

【 摘 要 】

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.