Gaia's Ancient Arbor

Gaia's Ancient Arbor enters the battlefield
tapped.
{t}: Add any combination of {w} and/or {g}
equal to the number of enchantments you control.
When this land becomes tapped for mana, target
creature you control with mana value less than
the amount of mana produced this way, gains
your choice of lifelink and vigilance, or
indestructible until end of turn.