Japanese oak vs tanbark oak

Japanese oak and tanbark oak both are nouns.

Word	Noun	Adjective	Verb	Adverb
Japanese oak	Yes	No	No	No
tanbark oak	Yes	No	No	No

As nouns, tanbark oak is a hypernym of Japanese oak; that is, tanbark oak is a word with a broader meaning than Japanese oak:

Japanese oak: small evergreen tree of China and Japan
tanbark oak: evergreen tree of the Pacific coast area having large leathery leaves; yields tanbark

Other hypernyms of Japanese oak include Lithocarpus densiflorus.

Japanese oak (noun)	tanbark oak (noun)
small evergreen tree of China and Japan	evergreen tree of the Pacific coast area having large leathery leaves; yields tanbark
oak with moderately light fine-grained wood; Japan