HR: 0830h
AN: B31C-0304    [PDF]
TI: Temperature Effects on Carbon Isotope Composition of Soil-respired Carbon Dioxide: an Incubation Study with arctic Soils
AU: * Richter, A
EM: andreas.richter@univie.ac.at
AF: Institute of Ecology, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
AU: Biasi, C
EM: cbiasi@pflaphy.pph.univie.ac.at
AF: Institute of Ecology, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
AU: Rusalimova, O
EM: olex-ru@nm.ru
AF: Institute of Soil Science, Street Sovejetskaya 18, Novosibirsk, 630099 Russian Federation
AU: Kaiser, T
EM: tranefel@pflaphy.pph.univie.ac.at
AF: Institute of Ecology, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
AU: Meyer, H
EM: hmeyer@pflaphy.pph.univie.ac.at
AF: Institute of Ecology, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
AU: Barsukov, P
EM: pavel-b@nm.ru
AF: Institute of Soil Science, Street Sovejetskaya 18, Novosibirsk, 630099 Russian Federation
AU: Wanek, W
EM: wwanek@pflaphy.pph.univie.ac.at
AF: Institute of Ecology, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
AB: Climatic conditions in arctic regions have been favorable for carbon sequestration in the geologic and historic past and an estimated 14% of the earth's terrestrial carbon is found in soils of tundra ecosystems. Climatic warming may change (or may have recently changed) tundra ecosystems from a sink to a source of CO$_{2}$. Up to now, little information exists on the nature of soil organic matter (SOM) respired and it is unclear so far if only a fraction of the soil carbon (e.g. labile SOM) is temperature-sensitive or if microorganisms are able to utilize more stable, recalcitrant C pools, that dominate the SOM in tundra soils. We conducted a long-term incubation experiment with intact soil cores of a shrub-moss tundra ecosystem at three different temperatures (2, 12 and 24$\deg$ C) and analyzed the isotopic signature of respired CO$_{2}$ to assess which fractions of SOM are available for decomposition at various temperatures. Despite a general increase in respiration rates with increasing temperatures, a substrate limitation of microorganisms occurred at 24$\deg$ C in mineral horizons, while no substrate limitation was observed in organic horizons. The $\delta^{13}$C values of CO$_{2}$ respired were negatively correlated to temperature, indicating the utilization of SOM fractions that were depleted in $^{13}$C at higher temperatures. Chemical fractionation showed that the most easily available substrates for microbial respiration were also most enriched in $^{13}$C. Our results therefore demonstrate that microorganisms may be able to mobilize recalcitrant soil carbon pools at elevated temperatures, indicating that a large proportion of tundra SOM is potentially mineralizable. When the $\delta^{13}$C values of respired CO$_{2}$ of soils, which were incubated either at 2$\deg$C or 24$\deg$C, were measured at 12$\deg$C, the isotopic signature, within a few hours, shifted to values normally found at this temperature. This may indicate that certain groups of soil microbes exhibit characteristic temperature optima and preferences for specific C compounds.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1823 Frozen ground
SC: Biogeosciences [B]
MN: 2003 Fall Meeting