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Does photosynthesis affect grassland soil-respired CO2 and its carbon isotope composition on a diurnal timescale?
Article first published online: 11 FEB 2009
DOI: 10.1111/j.1469-8137.2008.02755.x
© The Authors (2009). Journal compilation © New Phytologist (2009)
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How to Cite
Bahn, M., Schmitt, M., Siegwolf, R., Richter, A. and Brüggemann, N. (2009), Does photosynthesis affect grassland soil-respired CO2 and its carbon isotope composition on a diurnal timescale?. New Phytologist, 182: 451–460. doi: 10.1111/j.1469-8137.2008.02755.x
Publication History
- Issue published online: 27 MAR 2009
- Article first published online: 11 FEB 2009
- Received: 3 October 2008Accepted: 11 December 2008
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Keywords:
- assimilate supply;
- δ13C;
- mountain grassland;
- pulse labelling;
- plant–soil carbon (C) transfer;
- soil respiration;
- tunable diode laser
Summary
- • Soil respiration is the largest flux of carbon (C) from terrestrial ecosystems to the atmosphere. Here, we tested the hypothesis that photosynthesis affects the diurnal pattern of grassland soil-respired CO2 and its C isotope composition (δ13CSR).
- • A combined shading and pulse-labelling experiment was carried out in a mountain grassland. δ13CSR was monitored at a high time resolution with a tunable diode laser absorption spectrometer.
- • In unlabelled plots a diurnal pattern of δ13CSR was observed, which was not explained by soil temperature, moisture or flux rates and contained a component that was also independent of assimilate supply. In labelled plots δ13CSR reflected a rapid transfer and respiratory use of freshly plant-assimilated C and a diurnal shift in the predominant respiratory C source from recent (i.e. at least 1 d old) to fresh (i.e. photoassimilates produced on the same day).
- • We conclude that in grasslands the plant-derived substrates used for soil respiratory processes vary during the day, and that photosynthesis provides an important and immediate C source. These findings indicate a tight coupling in the plant–soil system and the importance of plant metabolism for soil CO2 fluxes.