salt tree vs shrub

salt tree and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
salt tree	Yes	No	No	No
shrub	Yes	No	No	No

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

salt tree: spiny shrub of the Caspian salt plains and Siberia having elegant silvery, downy young foliage and mildly fragrant pink-purple blooms
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of salt tree include bush.

salt tree (noun)	shrub (noun)
spiny shrub of the Caspian salt plains and Siberia having elegant silvery, downy young foliage and mildly fragrant pink-purple blooms	a low woody perennial plant usually having several major stems