subalpine fir vs silver fir

subalpine fir and silver fir both are nouns.

Word	Noun	Adjective	Verb	Adverb
subalpine fir	Yes	No	No	No
silver fir	Yes	No	No	No

As nouns, silver fir is a hypernym of subalpine fir; that is, silver fir is a word with a broader meaning than subalpine fir:

subalpine fir: medium-tall timber tree of the Rocky Mountains having a narrowly conic to columnar crown
silver fir: any of various true firs having leaves white or silvery white beneath

subalpine fir (noun)	silver fir (noun)
medium-tall timber tree of the Rocky Mountains having a narrowly conic to columnar crown	any of various true firs having leaves white or silvery white beneath