Camas-douglas fir-fire model

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In the Pacific Northwest region of the United States, Indigenous peoples have engaged in burning to maintain prairies which have reciprocol relationships with Indigenous peoples. The prairies have and continue to provide important food and medicine sources for humans and more-than-human animals, and Indigenous peoples have maintained the prairies since time immemorial through practices like harvesting responsibly and controlled burning.

When Euro-american settlers arrived in the Pacific Northwest, they removed Indigenous peoples from much of our land and confined Indigenous peoples to particular areas. In doing so, they (mostly) did not themselves take up the maintenance of the camas prairies in much of the land they privatized. As a result, the vast majority of camas prairies in the Pacific Northwest region have been taken over by the built environment, Douglas fir forests, and other native and non-native invasive plants, essentially turning the prairie land into forested land where it wasn't built on or turned into monoculture agricultural fields.

This model focuses on the relationships between humans who engage in burning practices, fire, camas, and Douglas fir, and is really a modification of Uri Wilenksy's fire model.

This model is meant to illustrate how human burning practices are an important aspect of prairie health because regularly burning a camas prairie (every 1 to 3 years) increases the growth rate of camas in the prairie and also kills the Douglas fir trees, which are native invasives in the prairie system. It should also show that when there are more Douglas fir trees, there are fewer camas plants, and vice versa.


In the model, there are different breeds of turtles: camas, Douglas fir, fire, and embers. There are sliders for the number of camas and Douglas fir that the model begins with at setup as well as for the dryness of the prairie and the reproduction rate of Douglas fir trees and camas plants.

When the model runs, a controlled burn will begin, which will burn the trees and camas plants. After the fire is done, the surviving plants will continue to grow and reproduce.


Click setup and then go. Use the sliders to alter variables.


Notice that how the population of douglas fir trees and camas are affected differently by the fire. Watch the graph for a different visual of the changes.


Try decreasing and increasing the dryness in the prairie, and also try change the number of camas and douglas fir trees you begin with. Note, thought, that in a typical camas prairie, there are far fewer douglas fir trees than camas plants because camas prairies need full sun to be healthy.


When a fire hits a camas prairie, the camas plants usually survive because the bulbs of the plant survive the fire underground -- only the aboveground portions of the plants die. Try to change the camas plants so that instead of dying when the fire touches them, they change shape into a bulb and then change back to a camas plant shape after waiting for some ticks.


This model features several different "breeds" of turtles that function in different ways.


Fire model by Uri Wilensky Wilensky, U. (1997). NetLogo Fire model. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.


Credit to the fire model cited above --- this model is based heavily on that one.

Reference for this model: McDaid-Morgan, N. (2019). NetLogo camas-douglas fir-fire model.

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globals [
  initial-trees   ;; how many trees (green patches) we started with
  burned-trees    ;; how many have burned so far

breed [fires fire]
breed [camas a-camas]
breed [embers ember]
breed [douglasfir a-douglasfir]
camas-own [age]
douglasfir-own [age]

To Setup
  create-camas number-of-camas [
   set age age + 0.5
    set shape "camas"
    set size 1.5
   set color 53
   move-to one-of patches

  create-douglasfir number-of-DouglasFir [
   set age age + 1
    set shape "tree fir"
    set size 1.5
   set color 52
   move-to one-of patches

;;  ask patches with [pycor < 0 and pycor > -10] [ set pcolor 56]
  ask patches [
    set pcolor 56]

   set-default-shape camas "camas"
  set-default-shape douglasfir "tree fir"
  ;; make some green trees
  ask patches with [(random-float 100) < dryness-of-prairie]
    [ set pcolor 57 ]
  ;; make a column of burning trees
  ask patches with [pxcor = min-pxcor]
    [ ignite ]
  ;; set tree counts
  set initial-trees count patches with [pcolor = green]
  set burned-trees 0

to go

  if not any? turtles  ;; either fires or embers
    [ stop ]

  ask fires
    [ask one-of neighbors4 ;with [pcolor = green]
      [ ignite ]
      set breed embers ]

    if ticks > 300 [

      ask fires [die]

  ask camas [
    set age age + 0.5
    if age > 15 [die]
    if any? fires-here [ ask camas-here [die]]
   ;;   set shape "bulb"
     ;; wait 10
     ;;set shape "camas"]]
    if random-float 100 < Camas-reproduction  [
      if any? neighbors with [count camas-here = 0] [
        ;;if random 100 < 10 [
        ask one-of neighbors with [count camas-here = 0] [
          sprout-camas 1 [
            set color 53
            set age 0
            move-to one-of neighbors
          set pcolor 56
        ;; ]

  ask DouglasFir [
    set age age + 1
    if age > 70 [die]
    if any? fires-here [ask douglasfir-here [die]]
    if random-float 150 < DouglasFir-reproduction [
      if any? neighbors with [count douglasfir-here = 0] [
        hatch-douglasfir 1 [
          set color 52
          set age 0
          move-to one-of neighbors]
        set pcolor 56



;; creates the fire turtles

to ignite  ;; patch procedure
  sprout-fires 1
    [ set color red
 set shape "fire" ]
  set pcolor black
  set burned-trees burned-trees + 1

;; achieve fading color effect for the fire as it burns

to fade-embers
  ask embers
    [ set color color - 0.5  ;; make red darker
      if color < red - 1.5     ;; are we almost at black?
        [ set pcolor color
          die ] ]

There is only one version of this model, created over 5 years ago by Nikki McDaid-Morgan.

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