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Titel |
Quantification of soil, root and litter respiration using natural variation in 13-C composition of CO2 fluxes and modelling |
VerfasserIn |
S. Blagodatsky, F. Albanito, D. Robinson, P. Smith |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250061532
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Zusammenfassung |
Heterotrophic and autotrophic components of soil respiration react differently to projected
changes in environmental conditions. In addition, individual heterotrophic components, such
as litter and soil organic matter in underlying mineral soil layers might contribute differently
to the respiration flux.Therefore, partitioning of surface soil CO2 flux in multiple source
components is necessary for the understanding of underlying mechanisms, and precise
modelling of the carbon turnover in soil. Isotopic methods based on natural variation in
carbon isotope composition (δ13C) of soil respiration have frequently been applied for
partitioning of soil respiration. However, the partitioning of three CO2 fluxes based on
differences in the abundance of one isotope (13C) in source members is not possible with a
simple balance approach (two end-member model). Recently, Albanito et al. (2012)
reported a three end-member mixing model for the estimation of root, soil and litter
contributions to the total CO2 flux from forest soil. This approach combines results of two
different methods: CO2 flux component integration and C budget calculation based
on the isotopic composition of components and the resulting flux. The estimation
of component fluxes by two methods helps to overcome the uncertainties linked
with either method: i.e. to account for the increase in respiration rate caused by
disturbances due to physical separation of components. Full consideration of possible
influences and corresponding calculations can be better completed with a help of
modeling.
Here, we report the application of simple data-driven model describing the decomposition
rate of the three components in order to quantify the disturbance effect in the component
integration CO2 flux method, and to improve the partitioning of soil, litter and root
respiration. The total surface CO2 flux and C isotope composition was measured using a
dual-chamber and cavity ring-down spectrometer (Albanito et al., 2012) for the sandy
calcareous regosol under a pine forest. Respiration rates and 13C signatures of the
components were estimated under field conditions similar to those for total flux measured by
the chamber method. The model gives estimates of the final CO2 flux from soil and its
isotopic composition using the input data for separated components: i.e. respiration rates of
litter, soil and roots. Mismatch between model prediction and field chamber measurements
can be taken into account by optimization of the “disturbance factor” values, the combination
of which is unique for each case. Finally, the corrected contribution of each flux
component can be obtained and linked with environmental and soil conditions. The most
susceptible to the disturbance component was SOM in mineral horizons, while
the root respiration was less sensitive. Litter contribution to the total flux was the
largest for the site under study. The results confirm the perspectives of the proposed
model approach in combination with the new method of Albanito et al. (2012) for
the quantification of ecosystem respiration response under the changing climatic
conditions.
Reference:
Albanito F., McAllister J.L., Cescatti A., Smith P., and Robinson D. 2012. Dual-chamber
measurements of δ13C of soil-respired CO2 partitioned using a field-based three end-member
model. Soil Biology and Biochemistry. In press |
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