guernsey elm vs elm tree

guernsey elm and elm tree both are nouns.

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

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

guernsey elm: 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 guernsey elm include elm.

guernsey elm (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