Fraxinus velutina vs ash tree

Fraxinus velutina and ash tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Fraxinus velutina	Yes	No	No	No
ash tree	Yes	No	No	No

As nouns, ash tree is a hypernym of Fraxinus velutina; that is, ash tree is a word with a broader meaning than Fraxinus velutina:

Fraxinus velutina: small shrubby ash of southwestern United States and northwestern Mexico
ash tree: any of various deciduous pinnate-leaved ornamental or timber trees of the genus Fraxinus

Other hypernyms of Fraxinus velutina include ash.

Fraxinus velutina (noun)	ash tree (noun)
small shrubby ash of southwestern United States and northwestern Mexico	any of various deciduous pinnate-leaved ornamental or timber trees of the genus Fraxinus