I’d look at the plans again. They are hard sometimes to interpret.
As others have said, an easement is a burden by others on “your ” property.
But the owner of the burdened property must maintain it.
From your question its not clear, so Ill give two scenarios.
If the easement runs through common property (that is any land not assigned to an owner) its the responsibility of the OC to maintain. That means its up to the OC to request and cut down the tree.
If the easement runs through your lot (say a rear courtyard) then its the lot owner responsibility – up to a point!.
Most strata plans state that the cubic space of the courtyards is limited to some height (around 3 metres is common). So any part of the tree above 3 metres is common property and therefore the responsibility of the OC.
{So you can cut down the first 3 meteres of a tree, but you must leave the upper section above 3 metres standing unless you get the permission of the OC}