Study Conclusions

We have shown an initial version of a model to assign treatments to tamarisk polygons. The two study sites selected provide a good contrast between a high density tamarisk infestation in accessible terrain, and a low density tamarisk infestation in inaccessible terrain. This contrast allowed us to exercise several elements of the model.

When assigning treatment types, the model considers the size, maximum slope, and tamarisk density of a polygon group. Aerial treatment is the least expensive, but it requires both high density and large area. For the John Martin SWA study area it was important to group polygons together to get large enough areas to justify aerial treatment. For the Gunnison River study area, few polygons had sufficient density to justify aerial treatment, so grouping did not affect the overall treatment cost.

There are several areas where improvements could be made to the model.

• The model only considers three treatment types: Aerial, Mechanical, and Manual. A future improvement is to expand the treatment types to include multiple types of mechanical such as mechanical mulching with herbicide, mechanical grap-and-pull, or mechanical raking. In addition, the model could consider the use of beetles as a biological control agent, or even using goats for infestations with a low height.
• The model fails to consider water as a barrier to movement. If this element were included the relative accessibility of certain sites would change, which would change the cost scalled by accessibility.