Sierra redwood vs big tree

Sierra redwood and big tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sierra redwood	Yes	No	No	No
big tree	Yes	No	No	No

As nouns, Sierra redwood and big tree are synonyms defined as:

Sierra redwood and big tree: extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism

Other synonyms of Sierra redwood include giant sequoia, Sequoia gigantea, Sequoia Wellingtonia, Sequoiadendron giganteum.

Sierra redwood (noun)	big tree (noun)
extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism	extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism