Limits...
Using an optimality model to understand medium and long-term responses of vegetation water use to elevated atmospheric CO2 concentrations.

Schymanski SJ, Roderick ML, Sivapalan M - AoB Plants (2015)

Bottom Line: Examples include stomatal conductance at short time scale (minutes), leaf area index and fine root distributions at longer time scales (days-months) and species composition and dominant growth forms at very long time scales (years-decades-centuries).As a result, the overall response of evapotranspiration to changes in environmental forcing may also change at different time scales.Without any model tuning or calibration, the model reproduced general trends deduced from FACE experiments, but, contrary to the widespread expectation that eCO2 would generally decrease water use due to its leaf-scale effect on stomatal conductance, our results suggest that eCO2 may lead to unchanged or even increased vegetation water use in water-limited climates, accompanied by an increase in perennial vegetation cover.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Systems Science, Swiss Federal Institute of Technology Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland Formerly at: Max Planck Institute for Biogeochemistry, Jena, Germany stan.schymanski@env.ethz.ch.

No MeSH data available.


Related in: MedlinePlus

Summary of effects of eCO2 on vegetation and water resources for constant climate. Effects specific to either water-limited or energy-limited catchments are in the respective coloured boxes. Note that decrease in transpiration per unit leaf area has an initial effect on increasing soil moisture in all catchments, whereas initially increased soil moisture and enhanced assimilation results in increasing leaf area and increased transpiration per ground area at the water-limited sites, reversing the initial effect on soil moisture.
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PLV060F5: Summary of effects of eCO2 on vegetation and water resources for constant climate. Effects specific to either water-limited or energy-limited catchments are in the respective coloured boxes. Note that decrease in transpiration per unit leaf area has an initial effect on increasing soil moisture in all catchments, whereas initially increased soil moisture and enhanced assimilation results in increasing leaf area and increased transpiration per ground area at the water-limited sites, reversing the initial effect on soil moisture.

Mentions: In summary, the results presented in this study suggest that the primary effects of eCO2 are a reduction of stomatal conductance and an enhancement of CO2 assimilation. The former leads to reduced transpiration per leaf area and an initially elevated soil moisture (Fig. 5), leading to increased drainage in energy-limited catchments. However, in water-limited catchments, elevated soil moisture is likely to result in increasing leaf area, while enhanced assimilation allows for the production of more and deeper roots, all of which would act to allow the vegetation to increase the light absorption by the canopy. The net effect is to either maintain, or even enhance, transpiration per unit ground area and to reduce soil moisture and drainage. Note that the relative increase in assimilation per unit ground area is very similar to relative increase in atmospheric CO2 concentrations at the dry sites (VIR, HS) but at the wet sites, the response in assimilation to a 20 % increase in atmospheric CO2 is more than halved, at around 10 % (Fig. 6).Figure 5.


Using an optimality model to understand medium and long-term responses of vegetation water use to elevated atmospheric CO2 concentrations.

Schymanski SJ, Roderick ML, Sivapalan M - AoB Plants (2015)

Summary of effects of eCO2 on vegetation and water resources for constant climate. Effects specific to either water-limited or energy-limited catchments are in the respective coloured boxes. Note that decrease in transpiration per unit leaf area has an initial effect on increasing soil moisture in all catchments, whereas initially increased soil moisture and enhanced assimilation results in increasing leaf area and increased transpiration per ground area at the water-limited sites, reversing the initial effect on soil moisture.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4497478&req=5

PLV060F5: Summary of effects of eCO2 on vegetation and water resources for constant climate. Effects specific to either water-limited or energy-limited catchments are in the respective coloured boxes. Note that decrease in transpiration per unit leaf area has an initial effect on increasing soil moisture in all catchments, whereas initially increased soil moisture and enhanced assimilation results in increasing leaf area and increased transpiration per ground area at the water-limited sites, reversing the initial effect on soil moisture.
Mentions: In summary, the results presented in this study suggest that the primary effects of eCO2 are a reduction of stomatal conductance and an enhancement of CO2 assimilation. The former leads to reduced transpiration per leaf area and an initially elevated soil moisture (Fig. 5), leading to increased drainage in energy-limited catchments. However, in water-limited catchments, elevated soil moisture is likely to result in increasing leaf area, while enhanced assimilation allows for the production of more and deeper roots, all of which would act to allow the vegetation to increase the light absorption by the canopy. The net effect is to either maintain, or even enhance, transpiration per unit ground area and to reduce soil moisture and drainage. Note that the relative increase in assimilation per unit ground area is very similar to relative increase in atmospheric CO2 concentrations at the dry sites (VIR, HS) but at the wet sites, the response in assimilation to a 20 % increase in atmospheric CO2 is more than halved, at around 10 % (Fig. 6).Figure 5.

Bottom Line: Examples include stomatal conductance at short time scale (minutes), leaf area index and fine root distributions at longer time scales (days-months) and species composition and dominant growth forms at very long time scales (years-decades-centuries).As a result, the overall response of evapotranspiration to changes in environmental forcing may also change at different time scales.Without any model tuning or calibration, the model reproduced general trends deduced from FACE experiments, but, contrary to the widespread expectation that eCO2 would generally decrease water use due to its leaf-scale effect on stomatal conductance, our results suggest that eCO2 may lead to unchanged or even increased vegetation water use in water-limited climates, accompanied by an increase in perennial vegetation cover.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Systems Science, Swiss Federal Institute of Technology Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland Formerly at: Max Planck Institute for Biogeochemistry, Jena, Germany stan.schymanski@env.ethz.ch.

No MeSH data available.


Related in: MedlinePlus