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Experimental vs. modeled water use in mature Norway spruce (Picea abies) exposed to elevated CO(2).

Leuzinger S, Bader MK - Front Plant Sci (2012)

Bottom Line: Rising levels of atmospheric CO(2) have often been reported to reduce plant water use.Here, we provide first results from a free air CO(2) enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS.Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station.

View Article: PubMed Central - PubMed

Affiliation: School of Applied Sciences, Auckland University of Technology Auckland, New Zealand ; Forest Ecology, ETH Zurich Zurich, Switzerland ; Institute of Botany, University of Basel Basel, Switzerland.

ABSTRACT
Rising levels of atmospheric CO(2) have often been reported to reduce plant water use. Such behavior is also predicted by standard equations relating photosynthesis, stomatal conductance, and atmospheric CO(2) concentration, which form the core of dynamic global vegetation models (DGVMs). Here, we provide first results from a free air CO(2) enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS. We monitored sap flow, stem water deficit, stomatal conductance, leaf water potential, and soil moisture in five 35-40 m tall CO(2)-treated (550 ppm) trees over two seasons. Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station. While the model predicted a stable reduction of transpiration of between 9% and 18% (at concentrations of 550-700 ppm atmospheric CO(2)), the combined evidence from various methods characterizing water use in our experimental trees suggest no changes in response to future CO(2) concentrations. The discrepancy between the modeled and the experimental results may be a scaling issue: while dynamic vegetation models correctly predict leaf-level responses, they may not sufficiently account for the processes involved at the canopy and ecosystem scale, which could offset the first-order stomatal response.

No MeSH data available.


Related in: MedlinePlus

Daily relative sap flow sums of the control and CO2-treated trees, both before (A) and after the CO2-treatment was initiated (B and C). Shown are the medians of each group (n = 5). The bold dotted line represents the 1:1 line, the solid line the linear fit (with dashed lines as 95% confidence intervals). The 1:1 line lies within the confidence intervals where data points are available, suggesting that there was no significant difference between treated and control trees in any of the three periods shown.
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Figure 1: Daily relative sap flow sums of the control and CO2-treated trees, both before (A) and after the CO2-treatment was initiated (B and C). Shown are the medians of each group (n = 5). The bold dotted line represents the 1:1 line, the solid line the linear fit (with dashed lines as 95% confidence intervals). The 1:1 line lies within the confidence intervals where data points are available, suggesting that there was no significant difference between treated and control trees in any of the three periods shown.

Mentions: Stem water deficit was related to the individual's stem radius at the beginning of the experiment and expressed in per mille change from the initial value. The resulting time series were decomposed into radius changes due to changes in stem water storage and a growth component according to the method outlined in (Zweifel et al., 2005). Essentially, this method considers periods between stem radius peaks as stem water deficits (see Figure 1 of Zweifel et al., 2005).


Experimental vs. modeled water use in mature Norway spruce (Picea abies) exposed to elevated CO(2).

Leuzinger S, Bader MK - Front Plant Sci (2012)

Daily relative sap flow sums of the control and CO2-treated trees, both before (A) and after the CO2-treatment was initiated (B and C). Shown are the medians of each group (n = 5). The bold dotted line represents the 1:1 line, the solid line the linear fit (with dashed lines as 95% confidence intervals). The 1:1 line lies within the confidence intervals where data points are available, suggesting that there was no significant difference between treated and control trees in any of the three periods shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472548&req=5

Figure 1: Daily relative sap flow sums of the control and CO2-treated trees, both before (A) and after the CO2-treatment was initiated (B and C). Shown are the medians of each group (n = 5). The bold dotted line represents the 1:1 line, the solid line the linear fit (with dashed lines as 95% confidence intervals). The 1:1 line lies within the confidence intervals where data points are available, suggesting that there was no significant difference between treated and control trees in any of the three periods shown.
Mentions: Stem water deficit was related to the individual's stem radius at the beginning of the experiment and expressed in per mille change from the initial value. The resulting time series were decomposed into radius changes due to changes in stem water storage and a growth component according to the method outlined in (Zweifel et al., 2005). Essentially, this method considers periods between stem radius peaks as stem water deficits (see Figure 1 of Zweifel et al., 2005).

Bottom Line: Rising levels of atmospheric CO(2) have often been reported to reduce plant water use.Here, we provide first results from a free air CO(2) enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS.Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station.

View Article: PubMed Central - PubMed

Affiliation: School of Applied Sciences, Auckland University of Technology Auckland, New Zealand ; Forest Ecology, ETH Zurich Zurich, Switzerland ; Institute of Botany, University of Basel Basel, Switzerland.

ABSTRACT
Rising levels of atmospheric CO(2) have often been reported to reduce plant water use. Such behavior is also predicted by standard equations relating photosynthesis, stomatal conductance, and atmospheric CO(2) concentration, which form the core of dynamic global vegetation models (DGVMs). Here, we provide first results from a free air CO(2) enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS. We monitored sap flow, stem water deficit, stomatal conductance, leaf water potential, and soil moisture in five 35-40 m tall CO(2)-treated (550 ppm) trees over two seasons. Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station. While the model predicted a stable reduction of transpiration of between 9% and 18% (at concentrations of 550-700 ppm atmospheric CO(2)), the combined evidence from various methods characterizing water use in our experimental trees suggest no changes in response to future CO(2) concentrations. The discrepancy between the modeled and the experimental results may be a scaling issue: while dynamic vegetation models correctly predict leaf-level responses, they may not sufficiently account for the processes involved at the canopy and ecosystem scale, which could offset the first-order stomatal response.

No MeSH data available.


Related in: MedlinePlus