BiteLifeCycle Class

BiteLifeCycle

Description

The BiteLifeCycle controls several aspects of the agent behavior. * voltinism: execution of the agent multiple times per year (e.g. for bark beetles with more than one generation per year) * timing of spread (frequency less than annual) * the mortality of cells (if not covered by the Biomass item )

controlling the timing of spreading

tbc

outbreak waves

Some agents show outbreak waves, i.e. phases (usually multiple years) with increased activity. This behavior is also implemented in Bite: to control the start and duration of outbreak waves, the properties
outbreakDuration and outbreakStart of the LifeCycle item can be used; the cell variable outbreakYears reflects the state of the cell and its value can be used to alter the behavior of the agent. outbreakYears is 0 for non-outbreak years (or if the outbreak mechanism is not used). The start of an outbreak is determined by the outbreakStart property. During an outbreak outbreakYears counts the years while in an outbreak phase (starting with 1). The end of an outbreak is initiated by the outbreakDuration property.

Example

The example uses Javascript to prescribe the start of each outbreak, and a variable outbreak length. The impact …

// helper function in global scope that is called 
// from the LifeCyclce item during the simulation
function outbreakSeries() {
   var _list = [10, 23, 37, 45]; // (dummy) years on which to start an outbreak
   for (i in _list)
      if (_list[i] > Globals.year)
        return _list[i]-Globals.year; // Globals.year: iLand global year counter
   return 0;
}

// agent definition
  ...
    lifecycle: new BiteLifeCycle({  
        ....
                outbreakStart: function(cell) { return outbreakSeries(); }, // force the start of outbreak waves at fixed years
                outbreakDuration: 'rnd(4,5.999)'   // the duration is 4 or 5 years
        }), ....
    
  // biomass item:
  growth: new BiteBiomass({ ...
  // lower mortality probability during outbreaks:
  mortality: function(cell) {
     if (cell.outbreakYears == 0) 
        return 0.9; 
     else
       return return (0.9/(1+Math.exp(-(cell.outbreakYears-2.5))));
  },
  ...

Setup

• voltinism (dynamic expression)

  tbc (not implemented)

• dieAfterDisturbance (boolean)

  if true, then the cell dies immediately after dispersal from the cell.

• spreadDelay (integer) (optional)

  if a non-0 value is provided, a cell can only start spreading when occupied for spreadDelay years.

• spreadFilter (dynamic expression) TODO: bad name

  Filter (cell context); a cell may spread with a probability given by that expression.

• spreadInterval (dynamic expression)

  controls how frequent a cell can spread; at least spreadInterval years have to be between consecutive spread from a cell.

• mortality (dynamic expression)

  The cell dies, if the expression (with cell context) returns true. Note that tree lists are not populated automatically (i.e. you need to call cell.reloadTrees() to have access to trees on the cell).

• outbreakDuration (dynamic expression, optional)

  The number of years that an outbreak lasts (evaluated at the begin of an outbreak). The value is truncated to an integer.

• outbreakStart (dynamic expression, optional)

  The number of years until the next outbreak (0 or missing means no outbreaks at all). Evaluated at the beginning of the simulation and after each outbreak wave.

Properties

• dieAfterDiespersla(item)

  The onSetup event is triggered after the setup of the item.

Variables

no variables

Events

• onSetup(item)

  The onSetup event is triggered after the setup of the item.

item is the BiteLfeCycle object.