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Carbon assimilation and turnover in grassland vegetation using an in situ 13 CO 2 pulse labelling system
Author(s) -
Ostle N.,
Ineson P.,
Benham D.,
Sleep D.
Publication year - 2000
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/1097-0231(20000815)14:15<1345::aid-rcm22>3.0.co;2-b
Subject(s) - chemistry , isotopes of carbon , isotope , tracer , environmental chemistry , shoot , vegetation (pathology) , stable isotope ratio , analytical chemistry (journal) , total organic carbon , horticulture , medicine , physics , pathology , quantum mechanics , nuclear physics , biology
A mobile laboratory was developed to administer a controlled flow of 13 C labelled CO 2 at ambient concentrations (∼350 ppm) in the field. The stable isotope delivery (SID) system consists of an isotope‐mixing unit with flow control to a series of 12 independent labelling chambers. In‐line CPU controlled infrared gas analysers allow automated measurement of chamber CO 2 concentrations and gas flow management. A preliminary experiment was established on an upland pasture located at the NERC Soil Biodiversity experimental site, Sourhope, UK, in August 1999. The objective of this investigation was to determine the magnitude of pulse‐derived C incorporation into a typical upland plant community. To achieve this, the SID system was deployed to pulse‐label vegetation with CO 2 enriched with 13 C (50 atom %) at ambient concentrations (∼350 ppm) on two consecutive days in August 1999. Samples of headspace CO 2 , shoot and root were taken on four occasions over a period of 28 days after 13 C labelling. These materials were then prepared for 13 C/ 12 C ratio determination by continuous‐flow/combustion/isotope ratio mass spectrometry (CF‐C‐IRMS). Results showed that pulse derived CO 2 ‐C was assimilated at a rate of 128 ± 32 µg g shoot‐C hour −1 . Dynamic samplings showed that pulse‐derived 13 C concentrations in the labelled plant tissues declined by 77.4 ± 6% after 48 hours. The rapid decline in 13 C concentrations in plant matter was the result of C loss from the plant in the form of respired CO 2 and root exudates, and dilution by subsequent unlabelled C assimilates. This novel system offers considerable potential for in situ tracer investigations. Copyright © 2000 John Wiley & Sons, Ltd.