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| Titel |
Increased nitrate availability in the soil of a mixed mature temperate forest subjected to elevated CO2 concentration (canopy FACE) |
| VerfasserIn |
Patrick Schleppi, Inga Bucher-Wallin, Frank Hagedorn, Christian Körner |
| 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 |
250076494
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| Zusammenfassung |
| In a mature temperate forest in Hofstetten, Switzerland, deciduous tree canopies were
subjected to a free-air CO2 enrichment (FACE) for a period of eight years. The effect of this
treatment on the availability of nitrogen (N) in the soil was assessed along three transects
across the experimental area, one under Fagus sylvatica, one under Quercus robur and Q.
petraea and one under Carpinus betulus. Nitrate, ammonium and dissolved organic N (DON)
were analysed in soil solution obtained with suction cups. Nitrate and ammonium were also
captured in buried ion-exchange resin bags. These parameters were related to the local
intensity of the FACE treatment as measured from the 13C depletion of dissolved inorganic
carbon in the soil solution, because the CO2 used for the treatment was depleted in 13C
(Schleppi et al., 2012).
Over the eight years of the experiment, the CO2 enrichment reduced DON concentrations,
did not affect ammonium, but induced higher nitrate concentrations, both in soil solution and
in resin bags. In the nitrate captured in the resin bags, the natural abundance of the isotope
15N strongly increased. This indicates that the CO2 enrichment accelerated net nitrification,
probably as an effect of the higher soil moisture resulting from the reduced transpiration
of the CO2-enriched trees. It is also possible that N mineralisation was enhanced
by root exudates (priming effect) or that the uptake of inorganic N by these trees
decreased slightly as the result of a reduced N demand for fine root growth. In this
mature deciduous forest we did not observe any progressive N limitation due to
elevated atmospheric CO2 concentrations; on the contrary, we observed an enhanced
N availability over the eight years of our measurements. This may, together with
the global warming projected, exacerbate problems related to N saturation and
nitrate leaching, although it is uncertain how long the observed trends will last in the
future.
Following the experiment with deciduous trees, a similar FACE experiment
was initiated on Picea abies trees. First results from this new experiment will be
presented.
REFERENCE
Schleppi, P., Bucher-Wallin, I., Hagedorn, F. & Körner C. 2012: Increased nitrate
availability in the soil of a mixed mature temperate forest subjected to elevated CO2
concentration (canopy FACE). Global Change Biology, 18, 757-768. |
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