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LSC 405 - Simulation Modeling
LECTURE NOTES
J. Wu
1. Population Dynamics, Community Structure, and Disturbance
The details of this model is documented in Chapter 14 of Grant et al. (1997).
Definitions:
r-selected species (or r-strategists): Species that
 reproduce early in their life span
 produce large numbers of usually small and short-lived offspring in a short period of
time, and
 usually have inferior competitive ability.
K-selected species (or K-strategists): Species that
 produce a few, often fairly large offspring
 invest a great deal of time and energy to assure offspring’s survival, and
 usually have superior competitively ability.
(1) Model Objectives
The General Objective:
 To facilitating understanding of the relationship among species life history
characteristics, interspecific competition, and disturbance.
Specific Objectives:
 To simulate the effects of the frequency of ecological disturbance on the
dynamics of populations, and the number and types of species (r- vs. Kselected), in a community over 500 years.
(2) Model Structure
 Use STELLA’s loop and tracing tools to help understanding model structure!
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A hypothetical ecological community in a 1-ha woodlot
2 K-selected (K1 and K2) and 3 r-selected species (R1, R2, and R3)
Maximum annual per capita natality rates: higher for r-species than for K-species
Minimum annual per capita mortality rates: same for both r- and K-species
Species interaction (competition):
 One directional: negative impact of K-species on r-species
 3 pairs of interactions: K1 on R1; K2 on R2; and K2 on R3
 Competition is modeled through competition coefficients and effective
population size (#indiv of a sp. + equivalent #indiv of its competitor sp.)
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Lecture Notes for LSC 405 Simulation Modeling --- J. Wu
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Periodic disturbance that affects all populations, killing 90% newborns but not
older adults
Current population size of each species = 100
(3) Model Simulations
To simulate the number and type of species present with the community over a 500-year
period with the following scenarios:
1) Disturbance time intervals = 9999 yrs (a large number implies no disturbance)
2) Disturbance time intervals = 30
3) Disturbance time intervals = 25
4) Disturbance time intervals = 20
5) Disturbance time intervals = 15
6) Disturbance time intervals = 10
7) Disturbance time intervals = 5
(4) Sensitivity Analysis
 Initial population size
 Natality and mortality parameters
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