hazel alder vs alder

hazel alder and alder both are nouns.

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

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

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

hazel alder (noun)	alder (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
	wood of any of various alder trees; resistant to underwater rot; used for bridges etc