Ulmus sarniensis vs elm tree

Ulmus sarniensis and elm tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ulmus sarniensis	Yes	No	No	No
elm tree	Yes	No	No	No

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

Ulmus sarniensis: a variety of the English elm with erect branches and broader leaves
elm tree: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of Ulmus sarniensis include elm.

Ulmus sarniensis (noun)	elm tree (noun)
a variety of the English elm with erect branches and broader leaves	any of various trees of the genus Ulmus: important timber or shade trees