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| Titel |
The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO2 efflux in a temperate grassland |
| VerfasserIn |
S. Burri, P. Sturm, U. E. Prechsl, A. Knohl, N. Buchmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 4 ; Nr. 11, no. 4 (2014-02-20), S.961-975 |
| Datensatznummer |
250117235
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| Publikation (Nr.) |
 copernicus.org/bg-11-961-2014.pdf |
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| Zusammenfassung |
Along with predicted climate change, increased risks for summer drought are
projected for Central Europe. However, large knowledge gaps exist in terms
of how drought events influence the short-term ecosystem carbon cycle. Here,
we present results from 13CO2 pulse labeling experiments at an
intensively managed lowland grassland in Switzerland. We investigated the
effect of extreme summer drought on the short-term coupling of freshly
assimilated photosynthates in shoots to roots as well as to soil CO2
efflux.
Summer drought was simulated using rainout shelters during two field seasons
(2010 and 2011). Soil CO2 efflux and its isotopic composition were
measured with custom-built chambers coupled to a quantum cascade laser
spectrometer (QCLAS-ISO, Aerodyne Research Inc., MA, USA). During the 90 min
pulse labeling experiments, we added 99.9 atom % 13CO2 to the
grass sward. In addition to the isotopic analysis of soil CO2 efflux,
this label was traced over 31 days into bulk shoots, roots and soil.
Drought reduced the incorporation of recently fixed carbon into the shoots,
but increased the relative allocation of fresh assimilates below ground
compared to the control grasslands. Contrary to our hypothesis, we did not
find a change of allocation speed in response to drought. Although drought
clearly reduced soil CO2 efflux rates, about 75% of total tracer
uptake in control plots was lost via soil CO2 efflux during 19 days
after pulse labeling, compared to only about 60% under drought
conditions. Thus, the short-term coupling of above- and below-ground
processes was reduced in response to summer drought. The occurrence of a
natural spring drought in 2011 lead to comparable albeit weaker drought
responses increasing the confidence in the generalizability of our findings. |
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