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F Ift:h Model: Nutritional Benefit of Old Biomass: Chapter 21. The Overshoot of The Kaibab Deer Population

This document summarizes a simulation model that examines the overshoot of the Kaibab deer population in the early 1900s. The fifth model adds a factor to account for the nutritional benefit of older biomass, which was ignored in previous models. With this addition, the model more closely matches the estimated peak population size from historical data. The older biomass is given a 25% nutrition value compared to new growth, representing its ability to fulfill 4 kilograms of nutritional needs for every 1 kilogram of new growth consumed. This additional element improves the model's ability to replicate the actual population dynamics observed.

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Rasool Masomi
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68 views1 page

F Ift:h Model: Nutritional Benefit of Old Biomass: Chapter 21. The Overshoot of The Kaibab Deer Population

This document summarizes a simulation model that examines the overshoot of the Kaibab deer population in the early 1900s. The fifth model adds a factor to account for the nutritional benefit of older biomass, which was ignored in previous models. With this addition, the model more closely matches the estimated peak population size from historical data. The older biomass is given a 25% nutrition value compared to new growth, representing its ability to fulfill 4 kilograms of nutritional needs for every 1 kilogram of new growth consumed. This additional element improves the model's ability to replicate the actual population dynamics observed.

Uploaded by

Rasool Masomi
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Chapter 21.

The Overshoot of the Kaibab Deer Population 279

consumption decline in the second half of the simulation owing to the collapse in the deer
population. This model comes close to the target pattern, but the peak population is somewhat:
less than the estimate from Rasmussen. The missing ingredient may be the nutritional
value of the older biomass.

80.000

consumption
of old biomass
60.000

40.000

�0.000 Figure 21.14. Stacked


graph of the biomass
consumed by deer.
0
1900 1910 1920 1930 1940

F ift:h Model: Nutritional Benefit of Old Biomass


Figure 21.15 shows the addition of an old-biomass nutrition factor. This was ignored in
t:he previous model; its value is set to 25% in the new model. This means that 4 kilograms
of older biomass deliver the equivalent benefit of 1 kilogram of new growth. The fraction of

_._-fullness effect lookup


fullness effect on bio
� fullness fraction _ maximum initial standing
biomass _..- productivity biomass
productivity + .,.__ biomass

/+ \_
intrinsic bio
new
+ biomass
+ +

Standing
productivity '-...... + - addition to Biomass
� standing
\
frofnew biomass +
biorrnss wilhin -...._ + consumption of
reach + new biomass \ old biomass + fr of added ongmal
ava1lable iomass remammg
+\�
fr of new + ,
,orage + �
fr of forage needs�
biomass within
met from new growth + consumption -....
�
reach - additional fr of added forage
� forage + forage required req consumed
�
'-...__ � (+ + availability /
equivalent fr of ratio �
-
� forage needs met /' + forage required per
+ deer per year
/ forage _+ ------
old biomass required � <Time>
+ number of ...- lookup for predators
nutrition factor �
deer net birth rate predators

/
lookup for 2nd shape

lookup for net deer deaths


birth rate + from predation �
area ___,._� deer density
� deer killed per
predator per year

Figure 21.15. The fifth model adds some nutritional benefit from the older biomass.

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