smooth alder vs alder

smooth alder and alder both are nouns.

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

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

smooth 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 smooth alder include alder tree.

smooth 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