Adding mirror/array modifier to collection containing forest emitter

Hi

Here is my dense scene

I’m un able to show you more than that as my blender file keeps crashing due to the load.

What i have done is created a forest scene using various emitters. The trees, grass etc has a very high poly count

All i want to do is add a mirror modifer and an array to the plane, and wish for the forest to do the same. I’ve spent 3 hours trying to join everything together and blender closes down/not responds.

Are there ways to, in my simple articulation, make the forest copy whatever the plane does - so if it mirrors, the forest mirrors, without joining them together.

I could swear there was a way to apply a modifier or link a modifer to a collection?

Please help :frowning: