Journal
NEW PHYTOLOGIST
Volume 182, Issue 2, Pages 451-460Publisher
WILEY
DOI: 10.1111/j.1469-8137.2008.02755.x
Keywords
assimilate supply; delta C-13; mountain grassland; pulse labelling; plant-soil carbon (C) transfer; soil respiration; tunable diode laser
Categories
Funding
- Austrian Science Fund (FWF) [P18756-B16]
- Tiroler Wissenschaftsfonds
- Austrian Science Fund (FWF) [P18756] Funding Source: Austrian Science Fund (FWF)
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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 (delta C-13(SR)). A combined shading and pulse-labelling experiment was carried out in a mountain grassland. delta C-13(SR) was monitored at a high time resolution with a tunable diode laser absorption spectrometer. In unlabelled plots a diurnal pattern of delta C-13(SR) 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 delta C-13(SR) 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.
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