Alnus serrulata vs alder tree

Alnus serrulata and alder tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Alnus serrulata	Yes	No	No	No
alder tree	Yes	No	No	No

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

Alnus serrulata: 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 Alnus serrulata include alder.

Alnus serrulata (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