Lenhart, K.; Kammann, C.; Boeckx, P.; Six, J. & Müller, C. (2016): <b>Quantification of ecosystem C dynamics in a long-term FACE study on permanent grassland</b>. <i>Rapid Communications in Mass Spectrometry</i> <b>30</b>, 963-972<br>DOI: <a href="http://dx.doi.org/10.1002/rcm.7515" target="_blank">http://dx.doi.org/10.1002/rcm.7515</a>.
Resource Description
Title:
Quantification of ecosystem C dynamics in a long-term FACE study on permanent grassland
F2Fdw ID:
62
Publication Date:
2016-01-19
License and Usage Rights:
FACE2FACE data user agreement.
Resource Owner(s):
Individual:
Lenhart, Katharina
Contact:
email:
Naiming.Yuan <at> geogr.uni-giessen.de
Individual:
Kammann, Claudia
Contact:
email:
claudia.kammann <at> hs-gm.de
Von-Lade Str. 1 65366 Geisenheim
Germany
RATIONALE: Because of the wide-ranging appearance and high soil organic carbon (C) content of grasslands, their ecosystems play an important role in the global C cycle. Thus, even small changes in input or output rates lead to significant changes in the soil C content, thereby affecting atmospheric [CO2]. Our aim was to examine if a higher C supply provided under elevated CO2 will increase the soil C pool. Special attention was given to respirational processes, where CO2 emission rates and its sources (plant vs. soil) were considered.<br/>
METHODS: The Giessen-FACE experiment started in 1998 with a moderate CO2 enrichment of +20% and +30% above ambient on an extensively managed grassland. The experiment consists of three control plots where no CO2 is applied, three plots where [CO2] is enriched by +20% and one plot receiving [CO2] +30%. To exclude initial CO2 step increase effects, a detailed examination of respirational processes over 30 months was carried out after 6 years of CO2 enrichment starting in June 2004. At that time, the ?13C signature of the enrichment-CO2 was switched from 25 ‰ to 48 ‰ without a concomitant change in CO2 concentration.<br/>
RESULTS: After 9 years, the fraction of new C under [CO2] +20% was 37 ± 5.4% in the top 7.5cm but this decreased with depth. No CO2 effect on soil carbon content was detected. Between June 2004 and December 2006, elevated [CO2] +20% increased the ecosystem respiration by 13%. The contribution of root respiration to soil respiration was 37 ± 13% (5 cm) and 43 ± 14% (10 cm) for [CO2] +20% and 35 ± 13% and 40 ± 13% for [CO2] +30%, respectively.<br/>
CONCLUSIONS: Our findings of an increased C turnover without a net soil C sequestration suggest that the sink strength of grassland ecosystems might decrease in the future, because the additional C may quickly be released as CO2 to the atmosphere.
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