The problem is in the SOIL PAT GAR AREA spline, used for the FT FWR & SHRUB object.
Some sub-splines are duplicated and stacked in the same position. This is causing precision errors in FP, generating different distributions randomly.
Please, check all your splines and remove duplicates. That should fix the problem.
One trick to "lock" Forest distributions, and be sure there are not unexpected changes while rendering, is to switch FP objects to Custom Edit mode.
That may be specially useful if you are preparing the scene for the render farm. Of course, this is valid only for static distributions.
One more thing: if you don't use camera clipping or other camera effects, you can increase performance a bit, turning off Camera->"Auto assign to active view", and clicking the "Clear" button, to remove the camera assignment.
In this way, Forest is not rebuilt witch each camera change (which is not necessary in this case).
I hope that helps.