 |
| Titel |
High temporal resolution tracing of xylem CO2 transport in oak trees |
| VerfasserIn |
Jasper Bloemen, Johannes Ingrisch, Michael Bahn |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128161
|
| Publikation (Nr.) |
 EGU/EGU2016-8118.pdf |
|
|
|
|
|
| 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 C flux of large magnitude whose role in C allocation yet is
unresolved.
In this study, we infused 13C labeled water into the stem base of five year old
potted oak (Quercus rubra) trees as a surrogate for respired CO2 to investigate the
role of respired CO2 transport in trees in C allocation. We used high-resolution
laser-based measurements of the isotopic composition of stem and soil CO2 efflux
combined with stem gas probes to monitor the transport of 13C label. The high
enrichment of the gas probes in the stem at the bottom of the canopy showed that the
label was transported upwards from the base of the tree toward the top. During its
ascent, the 13C label was removed from the transpiration stream and lost to the
atmosphere at stem level, as was observed using the stem CO2 efflux laser-based
measurements.
This study is the first to show results from tracing xylem CO2 transport in trees at high
temporal resolution using a 13C labeling approach. Moreover, they extend results from
previous studies on internal CO2 transport in species with high transpiration rates like poplar
to species with lower transpiration rates like oak. Internal transport of CO2 indicates that the
current concepts of the tree C allocation need to be revisited, as they show that current gas
exchange approach to estimating above- and belowground autotrophic respiration is
inadequate. |
|
|
|
|
|
|