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| Titel |
Effect of water and heat transport processes on methane emissions from paddy soils: a process-based model analysis |
| VerfasserIn |
Anacleto Rizzo, Fulvio Boano, Roberto Revelli, Luca Ridolfi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072045
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| Zusammenfassung |
| High CH4 fluxes are emitted from paddy fields worldwide and represent a considerable issue
for the rice production eco-sustainability. Water and heat transport fluxes are known to
strongly influence biogeochemical cycles in wetland environments, and therefore also CH4
emissions from paddy soils. Water percolation affects the dynamics of many compounds (e.g.
DOC, O2) influencing CH4 fate. On the other hand, heat fluxes strongly influence CH4
production in submerged rice crops, and lowering ponding water temperature (LPWT) can
reduce microbial activities and consequently decrease CH4 emissions. Moreover, as long as
the optimal temperature range for rice growth is maintained, LPWT can lower CH4
emissions without rice yield limitation. Hence, a process-based model is proposed and
applied to investigate the role of water flow on CH4 emissions, and to analyse
the efficiency of LPWT as mitigation strategy for CH4 production and release.
The process-based model relies on a system of partial differential mass balance
equations to describe the vertical dynamics of the chemical compounds leading to CH4
production. Many physico-chemical processes and features characteristic of paddy
soil are included: paddy soil stratigraphy; spatio-temporal variations of plant-root
compartment; water and heat transport; SOC decomposition; heterotrophic reactions in both
aerobic and anaerobic conditions; root radial oxygen loss; root solute uptake; DOC
root exudation; plant-mediated, ebullition, and diffusion gas exchange pathways.
LPWT is included as a temperature shift subtracted directly to the ponding water
temperature. Model results confirm the importance of water flow on CH4 emission, since
simulations that do not include water fluxes show a considerable overestimation of CH4
emissions due to a different DOC spatio-temporal dynamics. Particularly, when
water fluxes are not modeled the overestimation can reach 67 % of the total CH4
emission over the whole growing season. Moreover, model results also suggest
that roots influence CH4 dynamics principally due to their solute uptake, while
root effect on advective flow plays a minor role. In addition, the analysis of CH4
transport fluxes show the limiting effect of upward dispersive transport fluxes on the
downward CH4 percolation. Finally, LPWT is confirmed to be a valid mitigation
strategy for CH4 emissions from paddy soils, since the reduction of CH4 emission
reach about -50 % with a LPWT equal to only 2°C over the whole growing season. |
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