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| Titel |
Soil-atmosphere trace gas exchange from tropical oil palm plantations on peat |
| VerfasserIn |
Yit Arn Teh, Frances Manning, Norliyana Zin Zawawi, Timothy Hill, Melanie Chocholek, Lip Khoon Kho |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110103
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| Publikation (Nr.) |
 EGU/EGU2015-10075.pdf |
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| Zusammenfassung |
| Oil palm is the largest agricultural crop in the tropics, accounting for 13 % of all tropical land
cover. Due to its large areal extent, oil palm cultivation may have important implications not
only for terrestrial stores of C and N, but may also impact regional and global exchanges of
material and energy, including fluxes of trace gases and water vapor. In particular, recent
expansion of oil palm into tropical peatlands has raised concerns over enhanced soil C
emissions from degradation of peat, and elevated N-gas fluxes linked to N fertilizer
application.
Here we report our preliminary findings on soil carbon dioxide (CO2), methane (CH4)
and nitrous oxide (N2O) fluxes from a long-term, multi-scale project investigating the C, N
and greenhouse gas (GHG) dynamics of oil palm ecosystems established on peat soils in
Sarawak, Malaysian Borneo. Flux chamber measurements indicate that soil CO2, CH4 and
N2O fluxes averaged 20.0 ± 16.0 Mg CO2-C ha-1 yr-1, 37.4 ± 29.9 kg CH4-C ha-1 yr-1
and 4.7 ± 4.2 g N2O-N ha-1 yr-1, respectively. Soil CO2 fluxes were on par with other
drained tropical peatlands; whereas CH4 fluxes exceeded observations from similar study
sites elsewhere. Nitrous oxide fluxes were in a similar range to fluxes from other drained
tropical peatlands, but lower than emissions from mineral-soil plantations by up to three
orders of magnitude.
Fluxes of soil CO2 and N2O were spatially stratified, and contingent upon the distribution
of plants, deposited harvest residues, and soil moisture. Soil CO2 fluxes were most heavily
influenced by the distribution of palms and their roots. On average, autotrophic
(root) respiration accounted for approximately 78 % of total soil CO2 flux, and
total soil respiration declined steeply away from palms; e.g. soil CO2 fluxes in
the immediate 1 m radius around palms were up to 6 times greater than fluxes in
inter-palm spaces due to higher densities of roots. Placement of harvest residues
played an important – but secondary – role in modulating soil CO2 fluxes; soil
respiration rates doubled in areas where harvest residues were deposited, reflecting
an enhanced input of labile organic matter for decomposition. In contrast, N2O
fluxes were best-predicted by the distribution of harvest residues, and were only
weakly related to plant distributions or soil moisture. For example, N2O fluxes from
harvest residue piles were up to twice of the overall plot-average. In contrast, N2O
fluxes showed no clear pattern around palms or in inter-palm spaces; this finding is
surprising because N fertilizers are applied within the 1 m radius around palms, and we
expected to observe enhanced N2O fluxes in areas of greater fertilizer input. This
suggests that palms may be a strong competitor for N in these ecosystems, and
that fertilizer application may more closely match overall plant demand than in
mineral-soil plantations. Overall, the spatial patterning of soil CO2 and N2O fluxes
implies that soil biogeochemical processes are predictably distributed in space,
potentially making it easier to model and constrain fluxes of these soil-derived GHGs. |
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