Populus alba vs poplar

Populus alba and poplar both are nouns.

Word	Noun	Adjective	Verb	Adverb
Populus alba	Yes	No	No	No
poplar	Yes	No	No	No

As nouns, poplar is a hypernym of Populus alba; that is, poplar is a word with a broader meaning than Populus alba:

Populus alba: a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces
poplar: any of numerous trees of north temperate regions having light soft wood and flowers borne in catkins

Other hypernyms of Populus alba include poplar tree.

Populus alba (noun)	poplar (noun)
a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces	any of numerous trees of north temperate regions having light soft wood and flowers borne in catkins
	soft light-colored non-durable wood of the poplar