Alnus crispa vs alder tree

Alnus crispa and alder tree both are nouns.

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

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

Alnus crispa: North American shrub with light green leaves and winged nuts
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 crispa include alder.

Alnus crispa (noun)	alder tree (noun)
North American shrub with light green leaves and winged nuts	north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant