Long-term 13C labeling provides evidence for temporal and spatial carbon allocation patterns in mature Picea abies

Mildner, Manuel and Bader, Martin K. F. and Leuzinger, Sebastian and Siegwolf, Rolf T. W. and Körner, Christian. (2014) Long-term 13C labeling provides evidence for temporal and spatial carbon allocation patterns in mature Picea abies. Oecologia, 175 (3). pp. 747-762.

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There is evidence of continued stimulation of foliage photosynthesis in trees exposed to elevated atmospheric CO2 concentrations; however, this is mostly without a proportional growth response. Consequently, we lack information on the fate of this extra carbon (C) acquired. By a steady application of a 13CO2 label in a free air CO2 enrichment (FACE) experiment, we traced the fate of C in 37-m-tall, ca. 110-year-old Picea abies trees in a natural forest in Switzerland. Hence, we are not reporting tree responses to elevated CO2 (which would require equally 13C labeled controls), but are providing insights into assimilate processing in such trees. Sunlit needles and branchlets grow almost exclusively from current assimilates, whereas shaded parts of the crowns also rely on stored C. Only 2.5 years after FACE initiation, tree rings contained 100 % new C. Stem-respiratory CO2 averaged 50 % of new C over the entire FACE period. Fine roots and mycorrhizal fungi contained 49–56 and 26–43 % new C, respectively, after 2.5 years. The isotopic signals in soil CO2 arrived 12 days after the onset of FACE, yet it contained only ca. 15 % new C thereafter. We conclude that new C first feeds into fast turnover C pools in the canopy and becomes increasingly mixed with older C sources as one moves away (downward) from the crown. We speculate that enhanced C turnover (its metabolic cost) along the phloem path, as evidenced by basipetal isotope signal depletion, explains part of the ‘missing carbon’ in trees that assimilated more C under elevated CO2.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Pflanzenökologie (Körner)
UniBasel Contributors:Körner, Christian and Mildner, Manuel
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:09 Oct 2017 06:50
Deposited On:18 Jul 2014 09:10

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