Siberian elm vs elm tree

Siberian elm and elm tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Siberian elm	Yes	No	No	No
elm tree	Yes	No	No	No

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

Siberian elm: fast-growing shrubby Asian tree naturalized in United States for shelter or ornament
elm tree: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of Siberian elm include elm.

Siberian elm (noun)	elm tree (noun)
fast-growing shrubby Asian tree naturalized in United States for shelter or ornament	any of various trees of the genus Ulmus: important timber or shade trees