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| Titel |
Effect of severe drought on carbon uptake by plants and carbon translocation towards soil in a model grassland and heathland |
| VerfasserIn |
Kavita Srivastava, Bruno Glaser, Guido Wiesenberg |
| 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 |
250102529
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| Publikation (Nr.) |
 EGU/EGU2015-1852.pdf |
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| Zusammenfassung |
| Extreme weather events such as severe drought likely become more frequent in the future.
This influences carbon (C) cycling in the plant-soil system, which is poorly understood so far.
Our objective was to study the potential impact of increasing drought intensity on C uptake
by plants and C translocation into soil. This was studied in a model grassland ecosystem
and a model heathland ecosystem that have been subjected to 14 weeks of severe
drought in 2011 in the Event I experiment in Bayreuth, Germany. The conceptual
approach included multiple13CO2 pulse labeling (in the first, the fifth and the ninth
week of drought simulation period) of plants exposed to drought conditions in order
to trace above- and belowground C uptake and allocation. Plant and soil samples
were analysed for their C content and stable carbon isotope composition (δ13C).
During the whole experiment, the δ13C values were 0.5‰ higher in heathland
soil compared to corresponding grassland soil due to plant input that also revealed
higher δ13C values. During the first four weeks of the severe drought δ13C values
increased by 1‰ in both model ecosystems and remained almost constant until
the end of the experiment. After the first 13CO2 pulse labeling the δ13C value
increased by 2‰ after two weeks in the grassland and 1‰ in the heathland soil. Six
weeks after labeling, δ13C values were 2‰ higher in grassland and heathland soils
compared to the corresponding non-labeled soils. The larger time-lag of the highest 13C
enrichment in heathland compared to grassland soil indicates the slower uptake
of C by plants and C translocation into soil, whereas the total C allocation was
identical for both model ecosystems exposed to drought after 6 weeks. After the
second 13CO2 pulse labeling (i.e. after five weeks of drought) the δ13C values
increased by less than 0.5‰ in both soils of the different model ecosystems within 2
weeks. This increase was not observable any more after four weeks of labeling in the
grassland and six weeks after labeling in heathland soil. This confirms the slower C
cycling in heathland vs. grassland plant-soil systems. The soil δ13C values did not
reveal any labeling of the soil after the third labeling in the ninth week any more,
clearly demonstrating the lack of any further C uptake and translocation at this
severeness of the drought. This study concludes that the manipulated drought scenario
led to reduced plant C uptake and C allocation in soil after ten to twelve weeks of
drought for grassland and heathland ecosystems, respectively. As the largest effects of
drought were observed within the first six weeks of the drought, one can conclude that
the typical 100 year extremes at the experimental site (42 days = 6 weeks) lead to
changes in C cycling, but the model ecosystems can resist and cycle C even longer. |
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