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Göteborgs universitets publikationer

Stomatal O3 uptake of forest trees under rising atmospheric CO2 and tropospheric O3

Författare och institution:
Johan Uddling (Institutionen för växt- och miljövetenskaper); R. M. Teclaw (-); K. S. Pregitzer (-); D. S. Ellsworth (-)
Publicerad i:
Schaub M, Kaennel Dobbertin M, Steiner D (Eds) 2008. Air Pollution and Climate Change at Contrasting Altitude and Latitude. 23rd IUFRO Conference for Specialists in Air Pollution and Climate Change Effects on Forest Ecosystems. Murten, Switzerland, 7-12 Sept 2008. Abstracts. Birmensdorf, Swiss Federal Research Institute WSL. 162 pp., s. 138
Konferensbidrag, övrigt
Sammanfattning (abstract):
The rise in concentrations of atmospheric CO2 ([CO2]) and tropospheric O3 ([O3]) observed in recent decades and predicted for coming decades may portend large alterations in plant canopy function. Stomata respond to increased intercellular [CO2] by partially closing, and stomatal conductance (gs) was consistently reduced by both elevated [CO2] and elevated [O3] in shorter-term experiments with plants grown in controlled environments or field chambers. Based on these findings, combined stomatal-photosynthesis models, predicting decreased gs in response to increased [CO2], have been incorporated into the third generation of land surface models that are used in general circulation models. Such models have been employed to predict improved ecosystem hydrology, increased continental runoff and reduced stomatal uptake of O3 under rising atmospheric [CO2]. The Aspen FACE experiment in Rhinelander, Wisconsin USA, offers a unique opportunity to study fully acclimated long-term tree responses to elevated [CO2] and [O3], alone and in combination, under ecologically realistic conditions. Contrary to expectations, stand-level tree water-use of pure aspen and mixed aspen-birch communities was increased under elevated [CO2] and not significantly affected by [O3] treatment after canopy closure (Uddling et al. 2008). Here, we report on treatment effects on gs estimated by three independent methods: leaf-level gas exchange, sap flux in combination with within canopy scaling, and leaf tissue stable carbon isotope composition in combination with photosynthesis modelling. Regardless of method used, gs was always lowest in the control treatment (ambient [CO2] and ambient [O3]), but the only statistically significant treatment effect was that elevated [CO2] increased carbon isotope-derived gs. These results contrast with expectations as well as reports of reduced gs in an early phase of the experiment (Noormets et al. 2001), and suggest that long-term cumulative effects on stand structure and hydraulic efficiency may be more important than expected primary stomatal closure responses to elevated [CO2] and [O3] for determining gs under possible future atmospheric conditions. Results from FACE studies with trees are reviewed with respect to gs and tree water use and it is concluded that expectations and predictions of reduced O3 sensitivity of forests under rising [CO2] are unduly optimistic.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
Biologiska vetenskaper ->
Ekologi ->
Terrestrisk ekologi
FACE, carbon dioxide, ozone, ozone uptake, stomatal conductance
Postens nummer:
Posten skapad:
2010-02-22 08:53

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