Pinus rigida vs pine tree

Pinus rigida and pine tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pinus rigida	Yes	No	No	No
pine tree	Yes	No	No	No

As nouns, pine tree is a hypernym of Pinus rigida; that is, pine tree is a word with a broader meaning than Pinus rigida:

Pinus rigida: large three-needled pine of the eastern United States and southeastern Canada; closely related to the pond pine
pine tree: a coniferous tree

Other hypernyms of Pinus rigida include pine, true pine.

Pinus rigida (noun)	pine tree (noun)
large three-needled pine of the eastern United States and southeastern Canada; closely related to the pond pine	a coniferous tree