hazel alder vs alder tree

hazel alder and alder tree both are nouns.

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

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

hazel alder: common shrub of the eastern United States with smooth bark
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 hazel alder include alder.

hazel alder (noun)	alder tree (noun)
common shrub of the eastern United States with smooth bark	north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant