red alder vs alder tree

red alder and alder tree both are nouns.

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

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

red alder: large tree of Pacific coast of North America having hard red wood much used for furniture
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

Other hypernyms of red alder include alder.

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