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| Titel |
Strong indications of nitrogen limited methane uptake in tropical forest soils |
| VerfasserIn |
E. Veldkamp, B. Koehler, M. D. Corre |
| 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 |
250071251
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| Zusammenfassung |
| Tropical forest soils contribute an estimated 6.2 Tg yr-1 (27%) to global methane (CH4)
uptake, which is large enough to alter the CH4 accumulation in the atmosphere if significant
changes would occur to this sink. Elevated deposition of inorganic nitrogen (N) to temperate
forest ecosystems has shown to reduce CH4 fluxes from forest soils, but almost no
information exists from tropical forest soils even though projections show that N deposition
will increase substantially in tropical regions. Here we report the results of a long-term,
ecosystem scale experiment in which we assess the impact of chronic N addition on soil CH4
fluxes from two old-growth tropical forests in Panama: a lowland forest on a deeply
weathered soil with control and 9-12-yr N addition, and a montane forest on a less-developed
volcanic soil with control and 1-4-yr N addition. CH4 fluxes from the lowland forest
control plots (-21.47 ± 1.57 μg CH4-C m-2 h-1) and the montane forest control
plots (-3.99 ± 3.40 μg CH4-C m-2 h-1) did not significantly differ from their
respective N-addition plots. In the lowland forest, chronic N addition did not lead to
inhibition of CH4 uptake; in contrast, a negative correlation of NO3- with CH4
fluxes in these plots suggests that higher NO3- availability may have stimulated
CH4 consumption and/or reduced CH4 production. Also in the montane forest, we
detected negative correlation of CH4 fluxes with NH4+ both in the organic layer and
mineral soil, which we interpret as evidence that CH4 consumption may have been
N limited. That chronic N addition did not lead to higher CH4 uptake at any of
these sites was probably caused by the large spatial variability of CH4 fluxes which
may have rendered treatment effect not statistically significant. Furthermore, in the
lowland forest soil CH4 uptake was limited by diffusion of CH4 from the atmosphere
into the soil, which was not alleviated by N addition. We conclude that in these
extremely different tropical forest ecosystems, there were strong indications of N
limitation on CH4 uptake and that based on these results it is unlikely that elevated N
deposition on tropical forests will lead to widespread inhibition of CH4 uptake. |
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