Betula pubescens vs birch tree

Betula pubescens and birch tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Betula pubescens	Yes	No	No	No
birch tree	Yes	No	No	No

As nouns, birch tree is a hypernym of Betula pubescens; that is, birch tree is a word with a broader meaning than Betula pubescens:

Betula pubescens: European birch with dull white to pale brown bark and somewhat drooping hairy branches
birch tree: any betulaceous tree or shrub of the genus Betula having a thin peeling bark

Other hypernyms of Betula pubescens include birch.

Betula pubescens (noun)	birch tree (noun)
European birch with dull white to pale brown bark and somewhat drooping hairy branches	any betulaceous tree or shrub of the genus Betula having a thin peeling bark