I´m new at VUE 7, a simple question, I create terrain, and after that i choose "Forest and green fields" as ECO system. But when I edit ECO system and choose populate I do not get any instances, It says 0 ? What am i doing wrong?

have you got it set on dynamic population? its a little button to the side which when selected creates the ecosystem when the picture renders and so shows a count of 0.

I have tried to check dynamic population on or off, but It doesen´t make any difference.. I attache my file. I want trees on the flat green area in front of maountain. But so far no luck...
 

can you put some screen dumps of your material setting please and perhaps also the scene?  that would probably be most helpful to everyone.

When I generate some default terrain, without editing It, and choose grass, and turn one material to ECO system, and add trees everything works OK. But in the same moment I edit the terrian from the beginning, I only end up with 0 instances in material editor.

I add one picture to show..

Sometimes when I can't an eco system to populate, I move the terrain up off the ground plane - like in "mid-air" , then hit populate.   Then I can move the terrain back to the ground.
For reason that seems to works in for me in Vue 7.

see if you have "Decay near foreign objects" ticked in the density panel.  Remove the tick and try again

It worked, with both suggestions I got, thank´s a lot. I wonder what decay is? to make such difference. However one more question, as you can see in my example i only have a small part of the terrain as raised up. How do I get trees only on this part, now they are scattered all over the terrain..

There is an altitude control for the eco in the environment tab.  Just move the slide so the minimum doesn go all the way to -1 on the left. The exact value depends on your terrain, a few trials will lead you to the right choice.
The 'decay' option helps you avoid populating areas where there is already an object. Eg you have a house in your scene, you wouldnt want the trees to grow through the house so you turn on this optins and the tree population will decrease as they get close to the house.