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| Titel |
Effects of elevated CO2 on soil organic matter turnover and plant nitrogen uptake: First results from a dual labeling mesocosm experiment |
| VerfasserIn |
Lucia Muriel Eder, Enrico Weber, Marion Schrumpf, Sönke Zaehle |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149118
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| Publikation (Nr.) |
 EGU/EGU2017-13440.pdf |
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| Zusammenfassung |
| The response of plant growth to elevated concentrations of CO2 (eCO2) is often constrained
by plant nitrogen (N) uptake. To overcome potential N limitation, plants may invest
photosynthetically fixed carbon (C) into N acquiring strategies, including fine root biomass,
root exudation, or C allocation to mycorrhizal fungi. In turn, these strategies may affect the
decomposition of soil organic matter, leading to uncertainties in net effects of eCO2 on C
storage.
To gain more insight into these plant-soil C-N-interactions, we combined C and N stable
isotope labeling in a mesocosm experiment. Saplings of Fagus sylvatica L. were exposed to a
13CO2 enriched atmosphere at near ambient (380 ppm) or elevated (550 ppm) CO2
concentrations for four months of the vegetation period in 2016. Aboveground and
belowground net CO2 fluxes were measured separately and the 13C label enabled partitioning
of total soil CO2 efflux into old, soil derived and new, plant-derived C. We used ingrowth
cores to assess effects of eCO2on belowground C allocation and plant N uptake in more
detail and in particular we evaluated the relative importance of ectomycorrhizal
associations. In the soil of each sapling, ingrowth cores with different mesh sizes
allowed fine roots or only mycorrhizal hyphae to penetrate. In one type of ingrowth
core each, we incorporated fine root litter that was enriched in 15N. Additionally,
total N uptake was estimated by using 15N enriched saplings and unlabeled control
plants.
We found that eCO2 increased aboveground net CO2 exchange rates by 19% and total soil
respiration by 11%. The eCO2 effect for GPP and also for NPP was positive (+23% and
+11%, respectively). By combining gaseous C fluxes with data on new and old C stocks in
bulk soil and plants through destructive harvesting in late autumn 2016, we will be able to
infer net effects of eCO2 on the fate of C in these mesocosms. Biomass allocation patterns
can reveal physiological responses to high C availability under potentially constrained N
availability. Together with data on biomass production within the ingrowth cores these results
elucidate mechanisms affecting soil C storage and plant N uptake under eCO2. |
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