alder tree vs red alder

alder tree and red alder both are nouns.

Word	Noun	Adjective	Verb	Adverb
alder tree	Yes	No	No	No
red alder	Yes	No	No	No

As nouns, red alder is a hyponym of alder tree; that is, red alder is a word with a more specific, narrower meaning than alder tree:

alder tree: north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant
red alder: large tree of Pacific coast of North America having hard red wood much used for furniture

alder tree (noun)	red alder (noun)
north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant	large tree of Pacific coast of North America having hard red wood much used for furniture