Andresen, L.C.; Yuan, N.; Seibert, R.; Moser, G.; Kammann, C.; Luterbacher, J.; Erbs, M. & Müller, C. (2018): <b>Biomass responses in a temperate European grassland through 17 years of elevated CO2</b>. <i>Global Change Biology</i> <b>24</b>, 3875-3885<br>DOI: <a href="http://dx.doi.org/10.1111/gcb.13705" target="_blank">http://dx.doi.org/10.1111/gcb.13705</a>.
Resource Description
Title:
Biomass responses in a temperate European grassland through 17 years of elevated CO2
Future increase in atmospheric CO2 concentrations will potentially enhance grassland<br/>
biomass production and shift the functional group composition with consequences<br/>
for ecosystem functioning. In the “GiFACE” experiment (Giessen Free Air Carbon<br/>
dioxide Enrichment), fertilized grassland plots were fumigated with elevated CO2<br/>
(eCO2) year-round during daylight hours since 1998, at a level of +20% relative to<br/>
ambient concentrations (in 1998, aCO2 was 364 ppm and eCO2 399 ppm; in 2014,<br/>
aCO2 was 397 ppm and eCO2 518 ppm). Harvests were conducted twice annually<br/>
through 23 years including 17 years with eCO2 (1998 to 2014). Biomass consisted of<br/>
C3 grasses and forbs, with a small proportion of legumes. The total aboveground biomass<br/>
(TAB) was significantly increased under eCO2 (p = .045 and .025, at first and<br/>
second harvest). The dominant plant functional group grasses responded positively at<br/>
the start, but for forbs, the effect of eCO2 started out as a negative response. The<br/>
increase in TAB in response to eCO2 was approximately 15% during the period from<br/>
2006 to 2014, suggesting that there was no attenuation of eCO2 effects over time,<br/>
tentatively a consequence of the fertilization management. Biomass and soil moisture<br/>
responses were closely linked. The soil moisture surplus (c. 3%) in eCO2 manifested<br/>
in the latter years was associated with a positive biomass response of both functional<br/>
groups. The direction of the biomass response of the functional group forbs changed<br/>
over the experimental duration, intensified by extreme weather conditions, pointing<br/>
to the need of long-term field studies for obtaining reliable responses of perennial<br/>
ecosystems to eCO2 and as a basis for model development.
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