Stomatal conductance by law of limiting functions after Jarvis

Model : JarvisStomatalConductance
Simile version : 4.0
Date added : 2004-11-21
Keywords : Stomatal conductance ; Ecophysiology ; Evapotranspiration ; Law of limiting factors ;

Description

An empirical model of conductance of water vapour etc. through stomata (leaf pores). The predicted conductance is the product of a maximum conducatance and a number of normalized functions. The functions are response curves to particular environmental variables. In this model the responses are to: photon flux density (PFD), vapour pressure deficit (VPD), leaf temperature and CO2 concentration.

To run the model download the following files to the same directory. Met.csv is required by the parameter file params.spf

Files

Model file Click on the icon to download the model file. (You will need Simile to examine and run the model. A free evaluation version is available from the products page.) Some browsers may attempt to display the model file, rather than open it in Simile; in this case, use the browser back button to return to this page, and use the context menu (invoked by right-clicking on the link) to save the target file to disk.
TestJarvisStomataModel.sml
Met.csv
params.spf
Displays.shf

Diagram

Equations

Equations in JarvisStomatal Conductance
 
Variable   Gs : Stomatal conductance to water vapour Jarvis model
	Gs = Gs_max*Gs_PFD*GsVPD*GsT*GsCO2 
	Where:
		Gs_PFD=GsPFD/Gs_PFD
		GsVPD=GsVPD/GsVPD
		GsT=GsT/GsT
		GsCO2=GsCO2/GsCO2 
	Comments:
		No comment 

Equations in Environment
 
Variable   SVP : Saturated Vapour Pressure
	SVP = 0.611*exp(17.27*Temperature/(Temperature+237.15)) 
	Comments:
		temperature is in degrees C  svp is the saturated vapour pressure,in kPa from the                                   Tetens' formula from Montieth and Unsworth, 1990, Principles of     Environmental Physics p10, adapted for T in deg C                  Values are within 1 Pa upto 35 deg C 
 
Variable   VPD
	VPD = SVP*(1-RH) 

Equations in GsPFD
 
Variable   Gs_PFD
	Gs_PFD = Gsl*(PFD+Gdark/Gsl)/(1+Gsl*(PFD+Gdark/Gsl)) 
	Where:
		PFD=../../Environment/PFD 
	Comments:
		No comment 

Equations in GsVPD
 
Variable   GsVPD
	GsVPD = g=1-(VPD-Dthresh)/(D0-Dthresh),max(min(g,1.0),0) 
	Where:
		VPD=../../Environment/VPD 

Equations in GsT
 
Variable   GsT
	GsT = g=(Temperature-Tmin)*(Tmax-Temperature)^p/((T0-Tmin)*(Tmax-T0)^p),min(max(g,0),1) 
	Where:
		Temperature=../../Environment/Temperature
		T0=Topt 
 
Variable   p
	p = (Tmax-Topt)/(Topt-Tmin) 

Equations in GsCO2
 
Variable   GsCO2
	GsCO2 = g=1-gsja*(CO2Conc-averageCO2),max(min(g,1.0),0.0) 
	Where:
		CO2Conc=../../Environment/CO2Conc 

Results

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