Simple degree-days model of temperature influence on development of plants and invertebrates

Model : DegreeDays1
Simile version : 4.0
Date added : 2004-10-18
Keywords : Degree-days ; Develoment, physiological ; Pests ; Basic System Dynamics ; Insects ;

Description

The development rate of plants and invertebrate animals often depends on amount of heat received while the ambient temperature is between minimum and maximum thresholds.

The number of degree-days is a commonly used statistic related to the development of plants and invertebrates. Degree-days, DD, is given by:

DD = ∫ Tt.dt

• T is temperature in degrees Celsius (could be Fahrenheit)
• t is time in days.

degree-days is then ^oC days or ^oF days.

The model presented here is very simple and assumes that the upper threshold temperature is not reached.

Files

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DegreeDays1_P.sml

Model package includes display configuration

Diagram

Equations

Equations in DegreeDays1_P

Equations in Development
 
Compartment   DegreeDays : Degree days
	Initial value = 0
	Rate of change =  + dDt on dt
	Comments:
		Also called temperature sum or less accurately "heat sum". 
 
Flow   dDt on dt : Rate of accumation of degree-days (degC)
	dDt on dt = max(T_m-T_thresh,0) 
	Where:
		T_m=../Environment/T_m 
 
Variable   Sdevelopment : State of development
	Sdevelopment = min(DegreeDays/DDreq,1) 
	Comments:
		Value = 0 to 1 

Equations in Environment
 
Variable   T_m : Mean daily temperature
	T_m = graph(ime()) 

Results

Web links

• University of California Integrated Pest Management Program

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