western larch vs larch

western larch and larch both are nouns.

Word	Noun	Adjective	Verb	Adverb
western larch	Yes	No	No	No
larch	Yes	No	No	No

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

western larch: tall larch of western North America have pale green sharply pointed leaves and oblong cones; an important timber tree
larch: any of numerous conifers of the genus Larix all having deciduous needlelike leaves

Other hypernyms of western larch include larch tree.

western larch (noun)	larch (noun)
tall larch of western North America have pale green sharply pointed leaves and oblong cones; an important timber tree	any of numerous conifers of the genus Larix all having deciduous needlelike leaves
	wood of a larch tree