By design, agriculture is designed to typify monoculture. The school yard lawn. Many grounds keepers not only have created a monoculture similar to what happens in the Rainforest, but they also invest huge amounts of time, effort, and money to keep it a monoculture. Hours are spent eliminating any plants other than that nice green grass. These are the same techniques that are used when the Rainforest is cleared for plantations of bananas or other foods for export.
Procedure Find a good green patch of lawn that has very few of any other plants growing in it.
This area will represent the Monoculture. The second area that you will need is an area which is not as well tended. An overgrown, unmowed, out of sight area is perfect. An area of weedy lawn will suffice. Try to not use an area with shrubs or trees as these will shade the ground and not allow for true comparisons.