Project Description

    To start our project we researched extensively on Russian Olives and its behavior. Soon we contacted Gary Hathorn and Jessie Owens from The San Juan County Extension Office for more information. We were lucky enough to go out and map Russian Olives with Ms. Owens to get an idea of how many trees to put in our model. Mr. Hawthorne gave us information on eradication methods he’s researched and worked with such as the cut-stump, basal bark, and foliar application methods.

    We chose to use Starlogo for our model because it works well for modeling environments and creates a visual aid. In our model, the environment consists of a river to which birds and Russian Olives are added. Both the starting number of Russian Olives and birds are controlled by sliders. When the setup button is pressed the trees (random ages) will grow on a places three patches or closer to the river.

    Once the “go” button is pressed, the Russian Olives gain age and energy while the birds fly around randomly. Bird steps are used to measure time. Ten bird steps equals a month. Russian Olives mature at three years of age. Once mature they can produce fruit. In the program it takes a tree 360 steps to mature. A tree’s energy equals it’s age until it reaches an energy of 1200 where it will discontinue its increasing energy.

    When a bird lands on a mature tree it can pick up a seed to be planted. After 10 steps (a month) the bird will drop the seed. If the seed lands on a fertile patch (3 or less patches away from river), it may grow. As the model runs more trees are planted, they mature, and birds disperse more seeds.

    The eradication method we chose, as mentioned before, is the cut-stump method. This method can be applied to either young or mature trees with a button. Only 94% of the trees will be treated due to cut-stump’s success rate according to Mr. Hawthorne. Once trees are affected, their shape changes to that of a sick tree (red and green) and after each step 20 energy units are decreased from the tree. Decreasing energy helps make the project more realistic because it allows the young trees with less energy to die more quickly like when real trees are treated. If trees have been sick for a random amount of time in a year or more, they may become well, turning into a young tree. This is very much like real life while Russian Olives may send up new sprouts even after being treated. Once a tree’s energy level is less than or equal to zero it will die.