Well, there are two ways you could use collections to group photos together (and you are correct that it just creates a reference to the photos, and no additional copies are created on disk). One is to create a regular collection and simply drag and drop the photos you want to go in that collection. It is easiest to do this from Grid view.

Another option is to create a smart collection. Think of a smart collection as a kind of saved search. You come up with the criteria that defines the smart collection and then all the photos that match that criteria are automatically added to that smart collection. If something about a photo should change causing it to no longer match the criteria it will be automatically removed from the collection. So, in your case, you could perhaps use a keyword that you apply to all natural landscapes, and then you could further refine it as your needs dictate, such as with capture date, a color label, and so on.

thanks Colette and Rob Sylvan for the tips.

I was hoping i can do a right click and direct to the collections i need..

anyway, i figured out the drag method.

I read some tutorial that suggest to put keywords so the images can be filtered and put in the same collection.

Check out lightroomers.com for very useful lightroom tutorials and tips too

thanks Colette and Rob Sylvan for the tips.

I was hoping i can do a right click and direct to the collections i need..

anyway, i figured out the drag method.

I read some tutorial that suggest to put keywords so the images can be filtered and put in the same collection.

You can do this without dragging.

You create the collection you want and then right click on the collection name in the left panel and select Set as Target Collection. Then, you may select images anywhere in your catalog and type B to add them to the target collection. Little bit more streamlined than drag and drop if there's one target at a time you want to put images into.