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| Titel |
Deforestation for oil palm alters the fundamental balance of the soil N cycle |
| VerfasserIn |
Liz Hamilton, Mark Trimmer, Chris Bradley, Gilles Pinay |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132237
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| Publikation (Nr.) |
 EGU/EGU2016-12726.pdf |
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| Zusammenfassung |
| Expansion of commercial agriculture in equatorial regions has significant implications for
regional nitrogen (N) budgets, particularly nitrous oxide (N2O) and nitric oxide (NO)
emissions, produced largely by microbial nitrification and denitrification. However, current
estimates of soil N turnover are poorly constrained in Southeast Asia for nitrogen gas (N2)
production and lesser known N transformations such as nitrate ammonification (DNRA) and
anaerobic ammonium oxidation (anammox).
We investigated changes in N availability and turnover following replacement of
tropical forest with oil palm plantations along a chronosequence of oil palm maturity
(3-months to 15-year-old stands) and secondary to primary forest succession in Sabah,
Malaysian Borneo. Samples were taken from ten sites during March and April 2012.
Using 15N tracing techniques, we measured rates of gross ammonium (NH4+) and
nitrate (NO3−) production (mineralisation and nitrification) and consumption (n= 8),
potential denitrification, DNRA and anammox (n= 12) in soil cores and slurries
respectively.
Gross mineralisation rates (0.05 – 3.08 g N m−2 d−1) remained unchanged in oil palm
relative to forests. However, a significant reduction in gross nitrification (0.04 – 2.31 g N m−2
d−1) and an increase in NH4+ immobilisation disrupt the pathway to N2 production
substantially reducing (by > 90%) rates of denitrification and anammox in recently planted
oil palm relative to primary forest. In forests, N2 produced via anammox was ∼30% of that
from denitrification highlighting the potential for anammox to contribute significantly to N2
production. NH4+ production rates from DNRA were over two orders of magnitude less than
N2 production rates indicating that denitrification is the primary dissimilatory nitrate
consumption process in these soils. Potential N2O emissions were greater than potential N2
production, remaining unchanged across the chronosequence and indicating an increased
N2O:N2 emission ratio when soils were first disturbed. These results are an important
precursor to studies providing improved estimates of regional N turnover and loss in
Southeast Asia which will have global implications for N biogeochemical cycling. |
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