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## NetLogo User Community Models

WHAT IS IT?

This project models a rural agricultural village. There is farmland (green), village area (black), and sky (light blue), and they are all connected to provide a simple yet realistic simulation of rural agriculture.

HOW TO USE IT

Click the SETUP button to setup crops, people, and clear the sky of clouds and precipitation.

The number-trees slider controls the number of crops in the farmland.

The number-humans slider controls the number of people present in the village.

THINGS TO NOTICE

Rainy season is between 100 days and 200 days

THINGS TO TRY

Leaving other parameters alone, change the grass-grow-rate and let the system stabilize again. Would you expect that there would now be more grass? More rabbits?

Change only the birth-threshold of the rabbits. How does this affect the steady-state levels of rabbits and grass?

With the current settings, the rabbit population goes through a damped oscillation. By changing the parameters, can you create an undamped oscillation? Or an unstable oscillation?

In the current version, each rabbit has the same birth-threshold. What would happen if each rabbit had a different birth-threshold? What if the birth-threshold of each new rabbit was slightly different from the birth-threshold of its parent? How would the values for birth-threshold evolve over time?

Now add weeds by making the sliders WEEDS-GROW-RATE the same as GRASS-GROW-RATE and WEEDS-ENERGY the same as GRASS-ENERGY. Notice that the amount of grass and weeds is about the same.

Now make grass and weeds grow at different rates. What happens?

What if the weeds grow at the same rate as grass, but they give less energy to the rabbits when eaten (WEEDS-ENERGY is less than GRASS-ENERGY)?

Think of other ways that two plant species might differ and try them out to see what happens to their relative populations. For example, what if a weed could grow where there was already grass, but grass couldn't grow where there was a weed? What if the rabbits preferred the plant that gave them the most energy?

Run the model for a bit, then suddenly change the birth threshold to zero. What happens?

NETLOGO FEATURES

Notice that every black patch has a random chance of growing grass or
weeds each turn, using the rule:

`       if random-float 1000 < weeds-grow-rate         [ set pcolor violet ]       if random-float 1000 < grass-grow-rate         [ set pcolor green ]`

RELATED MODELS

Wolf Sheep Predation is another interacting ecosystem with different rules.

HOW TO CITE

If you mention this model in an academic publication, we ask that you include these citations for the model itself and for the NetLogo software:
- Wilensky, U. (2001). NetLogo Rabbits Grass Weeds model. http://ccl.northwestern.edu/netlogo/models/RabbitsGrassWeeds. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
- Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.