Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas set aside as wildlife habitat.

What is the meaning of

set aside as wildlife habitat."

Before omitting which, what was the original sentence? I think it is correct to say:

Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas which are set aside as wildlife habitat.

Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas set aside as wildlife habitat.

What is the meaning of

set aside as wildlife habitat."

Before omitting which, what was the original sentence? I think it is correct to say:

Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas which are set aside as wildlife habitat.

It is edited version.

Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas in which they are set aside as wildlife habitat.

in the above sentence, Which noun do "they" refer to?

What is the meaning of

"in which they are set aside as wildlife habitat."

and is it correct to say and rephrase it like this:

Smaller quantities are used in forestry, pasture systems, and management of areas set aside wildlife habitat.

and why is it correct or nor? thank you.

Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas set aside as wildlife habitat.

What is the meaning of

set aside as wildlife habitat."

Before omitting which, what was the original sentence? I think it is correct to say:

Smaller quantities (of herbicides) are used in forestry, pasture systems, and management of areas which are set aside as wildlife habitat.