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Simple degree-days model of temperature influence on development of plants and invertebrates
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.
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
University of California Integrated Pest Management Program [1] [1] http://www.ipm.ucdavis.edu/WEATHER/ddconcepts.html
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 degreedays1_p_sml_22771.sml | 146.7 KB |