The only mention of spell concentration in the Wild Shape feature is that using it does not break your concentration.

Can you maintain concentration while wild shape?

Using Wild Shape doesn't interrupt your concentration on a spell, so yes, guardian of nature is not stopped by Wild Shape.

Can druids concentrate in wild shape?

When your druid reaches 18th level, they will additionally be able to cast spells in their Wild Shape form. ... Usually, you cannot cast spells whilst in Wild Shape mode. (Though certain features allow you to do so.) However, any concentration spells you've already cast in normal form remain.