1Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand
2School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
*These authors contributed equally to this work.
Abstract. Since substrates for respiration are supplied mainly by recent photo-assimilates, there is a strong but time-lagged link between short-term above- and belowground carbon (C) cycling. However, regulation of this coupling by environmental variables is poorly understood. Whereas recent studies focussed on the effect of drought and shading on the link between above and belowground short-term C cycling, the effect of temperature remains unclear.
We used a 13CO2 pulse-chase labelling experiment to investigate the effect of a sudden temperature change from 25 °C to 10 °C on the short-term coupling between assimilatory C uptake and respiratory loss. The study was done in the laboratory using two month old perennial rye-grass plants (
Cold temperature (10 °C) reduced the short-term coupling between shoot and roots by delaying belowground transfer of recent assimilates and its subsequent respiratory use, as indicated by the δ13C signal of root respiration (δ13CRR). That is, the time-lag from the actual shoot labelling to the first appearance of the label in 13CRR was about 1.5 times longer under cold temperature (time-lags of 1 h and 1.5 h in the warm and cold treatments, respectively). Moreover, analysis of bulk shoot and root material revealed that plants at cold temperature invest relatively more carbon into respiration compared to growth or storage.
These results increase our understanding of environmental controls on the link between short-term above- and belowground C cycling.