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| Titel |
High temporal resolution tracing of up-and downward carbon transport in oak trees |
| VerfasserIn |
Jasper Bloemen, Johannes Ingrisch, Michael Bahn |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151012
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| Publikation (Nr.) |
 EGU/EGU2017-15551.pdf |
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| Zusammenfassung |
| Carbon (C) allocation defines the flows of C between plant organs and their storage pools and
metabolic processes and is therefore considered as an important determinant of forest C
budgets and their responses to climate change. In trees, assimilates derived from leaf
photosynthesis are transported via the phloem to above- and belowground sink tissues, where
partitioning between growth, storage, and respiration occurs. At the same time, root- and
aboveground respired CO2 can be dissolved in water and transported in the xylem tissue,
thereby representing a secondary C flux of large magnitude. The relative magnitude of
both fluxes in a same set of trees and their concurrent role in C allocation remains
unclear.
In this study, we 13C pulse labeled five year old potted oak (Quercus rubra) trees to
investigate both the role of C transport via the phloem and xylem in C allocation. To this end
trees were randomly assigned to two 13C labeling experiments: 1) a canopy labeling
experiment using transparent canopy chambers and 2) a stem labeling experiment based on
the infusion of 13C labeled water in the stem base. We used high-resolution laser-based
measurements of the isotopic composition of stem and soil CO2 efflux to monitor both the
down-and upward transport of 13C label. Additional tissue samples at stem, canopy and root
level were analyzed to validate the assimilation of the label in tree tissues during transport.
Overall, after both labeling experiments enrichment was observed in both stem
and soil CO2 efflux, showing that the 13C label was removed from both xylem
and phloem transport during up- and downward transport, respectively. Higher
enrichments of CO2 efflux were observed after stem labeling as compared to canopy
labeling, which implies that xylem transport strongly contributes to C lost to the
atmosphere.
This study is the first to show combined results from tracing of xylem and phloem transport
of C for a same set of trees at high temporal resolution using a 13C labeling approach.
Moreover, they extend results from previous studies on the tracing of phloem transport in
trees to a tracing of both xylem and canopy transport as well as results from studies on the
internal CO2 transport in species with high transpiration rates like poplar to species with
lower transpiration rates like oak. The results further demonstrate the complex interplay of
phloem and xylem transport of carbon and its role for the emission of respired CO2 from
trees into the atmosphere. |
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