Never specified.
Besides. A plane whos environment you control...
The native earth thing comes from vampire lore outside of the game. It was originally referring to dirt from the vampire's original grave. The vampire is supposed to be attached to a physical location, and not able to go wandering the world (or, if they do, they risk losing the native earth they bring along, and not being able to get more.
This lore, of course, comes from a tradition where there is no planar travel or control of planes, or magical transformation of Earth. Traditionally, the vampire is stuck, or at risk. Such is the price of the power of undeath.
Then, to be in the proper spirit of the thing, we should make this extremely difficult for the vampire to pull off. And I'm not sure "drain a bunch of humans" is really a price - I mean the vampire wants to drain people anyway, right?
I suggest that the ritual be more about changing the vampire than the dirt - to have different native earth, what counts as "home" for the vampire should change to the new location.