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| Titel |
What consequences can have small changes in heterotrophic respiration on the global carbon cycle? |
| VerfasserIn |
Caroline Roelandt, Jerry Tjiputra |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054124
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| Zusammenfassung |
| Soil is the largest global pool of terrestrial C and the soil organic C pool (approximately 2300
Pg of C, Davidson and Janssens, 2006) is at least three times larger than the size of the
atmospheric carbon pool. The heterotrophic respiration (RH), the conversion of soil organic
carbon to CO2 by the soil microbial community, depends on organic matter recalcitrance, on
soil temperature and moisture. Because of its strong sensitivity to temperature, it is believed
that the carbon transfer of from soils to the atmosphere due to the potential increase in global
temperatures could counterbalance the global NPP. The terrestrial biosphere would then
become a net source of carbon.
Global carbon cycle models of terrestrial ecosystems use empirical formulations, for the
dependence of RH on temperature, resting on empirical relationship obtained by curve-fitting
observed respiration rates and temperature. This leads to the question “how well could
these formulations simulate RH in a changing climate?” No one can answer to this
question today since there is no consensus on a mechanistic relationship able to
describe RH in a single model at the global scale. Inversely can we explore the
impact of changes in decomposition rates on the behavior of an Earth system Model
(ESM)?
To answer this question we used the “Bergen Climate Model – Carbon” (BCM-C,
Tjiputra et al., 2010). The BCM-C consists of global atmospheric and oceanic general
circulation models coupled to oceanic and terrestrial carbon cycle models (Tjiputra et al.,
2010). This ESM is able to interactively simulate the known global carbon-cycles processes,
including the radiative feedback necessary for climate change simulations. The terrestrial
carbon cycle is simulated with the Lund-Postdam-Jena Model (LPJ) (Sitch et al., 2003). LPJ
is run at a horizontal resolution of approximately 2.5Ë Ã2.5Ë with monthly model time step.
In LPJ, SOM decomposition follows a first order kinetics that is soil temperature and
moisture dependent. Temperature dependence follows the Arrhenius relationship modified by
Lloyd and Taylor (1994).
For this study, we modified the SOM decomposition dependence to soil temperature
by a constant factor: R: ±15%, ±10%, and 0%. These modified decomposition
rates are in the range of those obtained by Portner et al. (2010) with a linearized
form of Lloyd and Taylor function. Two series of multi-century simulations were
realized with the different values of R: 1) Simulations with pre-industrial climate
forcings (i.e., atmospheric CO2 concentration at 284.7 ppm, an estimated value
for year 1850). 2) Fully interactive simulations based on historical and SRES-A2
emission scenario (only for 0% and ± 5% sensitivity factor). These 10 simulations will
show us how a small change in RH can have consequences on the global carbon
cycle.
References:
Davidson, E. A., and I. A. Janssens (2006), Temperature sensitivity of soil carbon
decomposition and feedbacks to climate change, Nature, 440, 165-173.
Lloyd, J. and J. A. Taylor (1994), On the Temperature Dependence of Soil Respiration,
Functional Ecology, 8(3), 315-323
Portner, H., Bugmann, H., and A. Wolf (2010), Temperature response functions introduce
high uncertainty in modelled carbon stocks in cold temperature regimes, Biogeosciences, 7,
3669–3684.
Sitch, S., et al. (2003), Evaluation of ecosystem dynamics, plant geography and terrestrial
carbon cycling in the LPJ dynamic global vegetation model, Global Change Biol., 9,
161–185.
Tjiputra, J.F. et al., (2010), Bergen Earth system model (BCM-C): model description and
regional climate-carbon cycle feedbacks assessment, Geosci. Model Dev., 3, 123–141. |
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