Limits...
Controls of evapotranspiration and CO2 fluxes from scots pine by surface conductance and abiotic factors.

Zha T, Li C, Kellomäki S, Peltola H, Wang KY, Zhang Y - PLoS ONE (2013)

Bottom Line: Water use efficiency was slightly higher in the dry season, with mean monthly values ranging from 6.67 to 7.48 μmol CO2 (mmol H2O)(-1) and a seasonal average of 7.06 μmol CO2 (μmol H2O)(-1).Mid summer drought reduced surface conductance and decoupling coefficient, suggesting a more biotic control of evapotranspiration and a physiological acclimation to dry air.Surface conductance remained low and constant under dry condition, supporting that a constant value of surface constant can be used for modelling transpiration under drought condition.

View Article: PubMed Central - PubMed

Affiliation: The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China. tianshanzha@bjfu.edu.cn

ABSTRACT
Evapotranspiration (E) and CO2 flux (Fc ) in the growing season of an unusual dry year were measured continuously over a Scots pine forest in eastern Finland, by eddy covariance techniques. The aims were to gain an understanding of their biological and environmental control processes. As a result, there were obvious diurnal and seasonal changes in E, Fc , surface conductance (gc ), and decoupling coefficient (Ω), showing similar trends to those in radiation (PAR) and vapour pressure deficit (δ). The maximum mean daily values (24-h average) for E, Fc , gc , and Ω were 1.78 mmol m(-2) s(-1), -11.18 µmol m(-2) s(-1), 6.27 mm s(-1), and 0.31, respectively, with seasonal averages of 0.71 mmol m(-2) s(-1), -4.61 µmol m(-2) s(-1), 3.3 mm s(-1), and 0.16. E and Fc were controlled by combined biological and environmental variables. There was curvilinear dependence of E on gc and Fc on gc . Among the environmental variables, PAR was the most important factor having a positive linear relationship to E and curvilinear relationship to Fc , while vapour pressure deficit was the most important environmental factor affecting gc . Water use efficiency was slightly higher in the dry season, with mean monthly values ranging from 6.67 to 7.48 μmol CO2 (mmol H2O)(-1) and a seasonal average of 7.06 μmol CO2 (μmol H2O)(-1). Low Ω and its close positive relationship with gc indicate that evapotranspiration was sensitive to surface conductance. Mid summer drought reduced surface conductance and decoupling coefficient, suggesting a more biotic control of evapotranspiration and a physiological acclimation to dry air. Surface conductance remained low and constant under dry condition, supporting that a constant value of surface constant can be used for modelling transpiration under drought condition.

Show MeSH

Related in: MedlinePlus

Water use efficiency (WUE) from May to September, calculated on the basis of a dry surface (PAR >200 µmol m−2 s−1, with zero precipitation above and under the canopy).Values are monthly averages. The error bars represent standard deviation.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3722186&req=5

pone-0069027-g010: Water use efficiency (WUE) from May to September, calculated on the basis of a dry surface (PAR >200 µmol m−2 s−1, with zero precipitation above and under the canopy).Values are monthly averages. The error bars represent standard deviation.

Mentions: WUE was calculated on the days when leaves were dry (PAR >200 µmol m−2 s−1 and total hourly rainfall both above canopy and under the canopy were 0). The mean monthly values of WUE ranged from 6.67 μmol CO2 (mmol H2O)−1 in May to 7.48 in October, with a mean value of 7.06 (Fig. 10).


Controls of evapotranspiration and CO2 fluxes from scots pine by surface conductance and abiotic factors.

Zha T, Li C, Kellomäki S, Peltola H, Wang KY, Zhang Y - PLoS ONE (2013)

Water use efficiency (WUE) from May to September, calculated on the basis of a dry surface (PAR >200 µmol m−2 s−1, with zero precipitation above and under the canopy).Values are monthly averages. The error bars represent standard deviation.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722186&req=5

pone-0069027-g010: Water use efficiency (WUE) from May to September, calculated on the basis of a dry surface (PAR >200 µmol m−2 s−1, with zero precipitation above and under the canopy).Values are monthly averages. The error bars represent standard deviation.
Mentions: WUE was calculated on the days when leaves were dry (PAR >200 µmol m−2 s−1 and total hourly rainfall both above canopy and under the canopy were 0). The mean monthly values of WUE ranged from 6.67 μmol CO2 (mmol H2O)−1 in May to 7.48 in October, with a mean value of 7.06 (Fig. 10).

Bottom Line: Water use efficiency was slightly higher in the dry season, with mean monthly values ranging from 6.67 to 7.48 μmol CO2 (mmol H2O)(-1) and a seasonal average of 7.06 μmol CO2 (μmol H2O)(-1).Mid summer drought reduced surface conductance and decoupling coefficient, suggesting a more biotic control of evapotranspiration and a physiological acclimation to dry air.Surface conductance remained low and constant under dry condition, supporting that a constant value of surface constant can be used for modelling transpiration under drought condition.

View Article: PubMed Central - PubMed

Affiliation: The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China. tianshanzha@bjfu.edu.cn

ABSTRACT
Evapotranspiration (E) and CO2 flux (Fc ) in the growing season of an unusual dry year were measured continuously over a Scots pine forest in eastern Finland, by eddy covariance techniques. The aims were to gain an understanding of their biological and environmental control processes. As a result, there were obvious diurnal and seasonal changes in E, Fc , surface conductance (gc ), and decoupling coefficient (Ω), showing similar trends to those in radiation (PAR) and vapour pressure deficit (δ). The maximum mean daily values (24-h average) for E, Fc , gc , and Ω were 1.78 mmol m(-2) s(-1), -11.18 µmol m(-2) s(-1), 6.27 mm s(-1), and 0.31, respectively, with seasonal averages of 0.71 mmol m(-2) s(-1), -4.61 µmol m(-2) s(-1), 3.3 mm s(-1), and 0.16. E and Fc were controlled by combined biological and environmental variables. There was curvilinear dependence of E on gc and Fc on gc . Among the environmental variables, PAR was the most important factor having a positive linear relationship to E and curvilinear relationship to Fc , while vapour pressure deficit was the most important environmental factor affecting gc . Water use efficiency was slightly higher in the dry season, with mean monthly values ranging from 6.67 to 7.48 μmol CO2 (mmol H2O)(-1) and a seasonal average of 7.06 μmol CO2 (μmol H2O)(-1). Low Ω and its close positive relationship with gc indicate that evapotranspiration was sensitive to surface conductance. Mid summer drought reduced surface conductance and decoupling coefficient, suggesting a more biotic control of evapotranspiration and a physiological acclimation to dry air. Surface conductance remained low and constant under dry condition, supporting that a constant value of surface constant can be used for modelling transpiration under drought condition.

Show MeSH
Related in: MedlinePlus