hickory pine vs pine tree

hickory pine and pine tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
hickory pine	Yes	No	No	No
pine tree	Yes	No	No	No

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

hickory pine: a small two-needled upland pine of the eastern United States (Appalachians) having dark brown flaking bark and thorn-tipped cone scales
pine tree: a coniferous tree

Other hypernyms of hickory pine include pine, true pine.

hickory pine (noun)	pine tree (noun)
a small two-needled upland pine of the eastern United States (Appalachians) having dark brown flaking bark and thorn-tipped cone scales	a coniferous tree