Western paper birch vs mountain birch

Western paper birch and mountain birch both are nouns.

Word	Noun	Adjective	Verb	Adverb
Western paper birch	Yes	No	No	No
mountain birch	Yes	No	No	No

As nouns, Western paper birch and mountain birch are synonyms defined as:

Western paper birch and mountain birch: birch of western United States resembling the paper birch but having brownish bark

Other synonyms of Western paper birch include Betula fontinalis, swamp birch, water birch, Western birch.

Western paper birch (noun)	mountain birch (noun)
birch of western United States resembling the paper birch but having brownish bark	birch of western United States resembling the paper birch but having brownish bark