black larch vs larch tree

black larch and larch tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
black larch	Yes	No	No	No
larch tree	Yes	No	No	No

As nouns, larch tree is a hypernym of black larch; that is, larch tree is a word with a broader meaning than black larch:

black larch: medium-sized larch of Canada and northern United States including Alaska having a broad conic crown and rust-brown scaly bark
larch tree: any of numerous conifers of the genus Larix all having deciduous needlelike leaves

Other hypernyms of black larch include larch.

black larch (noun)	larch tree (noun)
medium-sized larch of Canada and northern United States including Alaska having a broad conic crown and rust-brown scaly bark	any of numerous conifers of the genus Larix all having deciduous needlelike leaves