Fraxinus oregona vs ash tree

Fraxinus oregona and ash tree both are nouns.

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

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

Fraxinus oregona: timber tree of western North America yielding hard light wood; closely related to the red ash
ash tree: any of various deciduous pinnate-leaved ornamental or timber trees of the genus Fraxinus

Other hypernyms of Fraxinus oregona include ash.

Fraxinus oregona (noun)	ash tree (noun)
timber tree of western North America yielding hard light wood; closely related to the red ash	any of various deciduous pinnate-leaved ornamental or timber trees of the genus Fraxinus