Alnus maritima vs alder tree

Alnus maritima and alder tree both are nouns.

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

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

Alnus maritima: shrub or small tree of southeastern United States having soft light brown wood
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 maritima include alder.

Alnus maritima (noun)	alder tree (noun)
shrub or small tree of southeastern United States having soft light brown wood	north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant