Attached Link: Reference Image Palm Island!

I have Esprit 6, but will try to answer this.  I have a terrain and I wanted to have the trees and bushes populate only the top of the terrain, which was an island. After I created the eco system and before I populated the terrain I changed the following setting.    

In the Advanced Materials Editor, under the tab named Environment, in the Group Attribute named Altitude constraint, I changed the setting of attribute named Altitude range to +.40 1.00.  The original setting -1.00 +1.00 setting is relative to the terrain you want to edit.  The first figure represents the bottom of the terrain, and the second figure represents the topmost part of the terrain.  Since My island was only about 100 feet high I changed the setting from -1.00 to +.40 and once populated all of the eco items lay on the topmost part of my island.  You may also have to change the Slop constraint if you have a gradual falloff on the terrain.

 

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