Vegetation and Disturbance - Environmental Modelling: Finding Simplicity in Complexity - page 234

Resource

B tot

Species

M

W

h

death

B

growth

d

g

Bmax

Figure 14.3 Model structure in the SIMILE graphical user interface.

i 3 Rubus ), W i the growth resource function (for each

species), g i the growth parameter, M i is the maximal
species biomass, B tot

= The changes of relative cover for the three species

were modelled under the same postfire conditions (plant
densities and grazing treatments) as the case study. The
simulation results are reported in Figure 14.4.

the sum of all species biomass

i = 1 B i ), B max is the maximum biomass of all species (the
system's carrying capacity), d i the death rate, h i the extra
loss of biomass due to grazing. For simplicity species differ
only in their growth parameters g i , the growth resource
effects W i and species carry capacity M i . Table 14.1 reports
the model components and inputs.

3

(

Individual-based modelling approach
In the previous example, based on the systems dynamic
approach, the vegetation was seen as an aggregation
of homogeneous entities (species cover) changing in a

Table 14.1 Model components and inputs.

Name Meaning Units Assigned value

kg m − 2

B biomass 0.01 (t = 0)

i species index - -

= = =

( i 1 Ulex, i 2Erica,i 3 Rubus )

month − 1 g growth rate [0.2,0.4,0.38]

W growth resource function - between 0 and 1

kg m − 2 M max species biomass [0.5,0.5,0.2]

kg m − 2 B tot total biomass -

kg m − 2 B max max biomass (system carry capacity) 1

month − 1 d death rate [0.1,0.1,0.1]

month − 1 h response to grazing pressure between 0 and 1