General:
* Tract - A large area of land
* Parcel - A small piece of land
* Estate - A large area of land, often with a house or buildings
* Domain - An area of land under control or ownership
Specific:
* Forest - For a collection of trees
* Meadow - For a collection of grass
* Desert - For a dry, barren area
* Farmland - For land used for agriculture
* Wasteland - For barren or desolate land
Figurative:
* Realm - For a large, powerful area of land
* Territory - For land controlled by a group or nation
Ultimately, the best collective noun for land will depend on the specific context and the type of land you are describing.