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Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna

Cernusak, Lucas A., Hutley, Lindsay B., Beringer, Jason and Tapper, Nigel J. (2006). Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna. Plant, Cell and Environment,29(4):632-646.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 38 times in Scopus Article | Citations

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IRMA ID 78220150xPUB29
Title Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna
Author Cernusak, Lucas A.
Hutley, Lindsay B.
Beringer, Jason
Tapper, Nigel J.
Journal Name Plant, Cell and Environment
Publication Date 2006
Volume Number 29
Issue Number 4
ISSN 0140-7791   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-33645382642
Start Page 632
End Page 646
Total Pages 15
Place of Publication Oxford
Publisher Blackwell Publishing
Field of Research 0607 - Plant Biology
HERDC Category C1 - Journal Article (DEST)
Abstract We measured stem CO2 efflux and leaf gas exchange in a tropical savanna ecosystem in northern Australia, and assessed the impact of fire on these processes. Gas exchange of mature leaves that flushed after a fire showed only slight differences from that of mature leaves on unburned trees. Expanding leaves typically showed net losses of CO2 to the atmosphere in both burned and unburned trees, even under saturating irradiance. Fire caused stem CO2 efflux to decline in overstory trees, when measured 8 weeks post-fire. This decline was thought to have resulted from reduced availability of C substrate for respiration, due to reduced canopy photosynthesis caused by leaf scorching, and to priority allocation of fixed C towards reconstruction of a new canopy. At the ecosystem scale, we estimated the annual above-ground woody-tissue CO2 efflux to be 275 g C m(-2) ground area year(-1) in a non-fire year, or approximately 13% of the annual gross primary production. We contrasted the canopy physiology of two co-dominant overstory tree species, one of which has a smooth bark on its branches capable of photosynthetic re-fixation (Eucalyptus miniata), and the other of which has a thick, rough bark incapable of re-fixation (Eucalyptus tetrodonta). Eucalyptus miniata supported a larger branch sapwood cross-sectional area in the crown per unit subtending leaf area, and had higher leaf stomatal conductance and photosynthesis than E. tetrodonta. Re-fixation by photosynthetic bark reduces the C cost of delivering water to evaporative sites in leaves, because it reduces the net C cost of constructing and maintaining sapwood. We suggest that re-fixation allowed leaves of E. miniata to photosynthesize at higher rates than those of E. tetrodonta, while the two invested similar amounts of C in the maintenance of branch sapwood.
Keywords eucalyptus
stem respiration
carbon-isotope discrimination
woody-tissue respiration
kakadu national-park
branch maintenance respiration
contrasting climates
plant respiration
rainfall gradient
pine forest
xylem sap
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Created: Wed, 28 Nov 2007, 14:16:08 CST