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| Titel |
Land use change and the impact on greenhouse gas exchange in north Australian savanna soils |
| VerfasserIn |
S. P. P. Grover, S. J. Livesley, L. B. Hutley, H. Jamali, B. Fest, J. Beringer, K. Butterbach-Bahl, S. K. Arndt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 1 ; Nr. 9, no. 1 (2012-01-25), S.423-437 |
| Datensatznummer |
250006674
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| Publikation (Nr.) |
 copernicus.org/bg-9-423-2012.pdf |
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| Zusammenfassung |
| Savanna ecosystems are subjected to accelerating land use change as human
demand for food and forest products increases. Land use change has been
shown to both increase and decrease greenhouse gas fluxes from savannas and
considerable uncertainty exists about the non-CO2 fluxes from the soil.
We measured methane (CH4), nitrous oxide (N2O) and carbon dioxide
(CO2) over a complete wet-dry seasonal cycle at three replicate sites
of each of three land uses: savanna, young pasture and old pasture
(converted from savanna 5–7 and 25–30 yr ago, respectively) in the
Douglas Daly region of Northern Australia. The effect of break of season
rains at the end of the dry season was investigated with two irrigation
experiments.
Land use change from savanna to pasture increased net greenhouse gas fluxes
from the soil. Pasture sites were a weaker sink for CH4 than savanna
sites and, under wet conditions, old pastures turned from being sinks to a
significant source of CH4. Nitrous oxide emissions were generally very
low, in the range of 0 to 5 μg N2O-N m−2 h−1, and under
dry conditions soil uptake of N2O was apparent. Break of season rains
produced a small, short lived pulse of N2O up to 20 μg N2O-N m−2 h−1, most evident in pasture soil. Annual cumulative soil
CO2 fluxes increased after clearing, with savanna (14.6 t CO2-C ha−1 yr−1) having the lowest fluxes compared to old pasture
(18.5 t CO2-C ha−1 yr−1) and young pasture (20.0 t CO2-C ha−1 yr−1). Clearing savanna increased soil-based greenhouse gas
emissions from 53 to ∼ 70 t CO2-equivalents, a 30% increase
dominated by an increase in soil CO2 emissions and shift from soil
CH4 sink to source. Seasonal variation was clearly driven by soil water
content, supporting the emerging view that soil water content is a more
important driver of soil gas fluxes than soil temperature in tropical
ecosystems where temperature varies little among seasons. |
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