Thanks haegerst, that turned out really well although it takes a bit of time to lay down foreign objects all over the path.  Shortly after posting my original message, I actually came up with something else that has been working so far for anyone else who may have this problem.  Here is what I did...

I duplicated the path/grass terrain in the exact spot as the original and then went into the terrain editor.  From there I selected 'picture' and used an inverse (black/white color reversal) bitmap of the path image and selected 'subtract' to eliminate the path region of the terrain from the duplicate copy (note that the ground level of the original and duplicate terrains must already be clipped).  Then I set up my ecosystem and made sure it would only plant from altitudes -0.98 to 1.00 so it would not place anything where the terrain was eliminated since that area is at -1.00.  This kept all the objects off of my path and the only negative I can see to this technique would be if the extra terrain object consisted of a huge number of polygons that would lower the resources below an acceptable level.