tree surgery vs tending

tree surgery and tending both are nouns.

Word	Noun	Adjective	Verb	Adverb
tree surgery	Yes	No	No	No
tending	Yes	Yes	No	No

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

tree surgery: treatment of damaged or decaying trees
tending: the work of providing treatment for or attending to someone or something

Other hypernyms of tree surgery include aid, attention, care.

tree surgery (noun)	tending (noun)
treatment of damaged or decaying trees	the work of providing treatment for or attending to someone or something

tree surgery (adjective)	tending (adjective)
	(usually followed by `to') naturally disposed toward