Nissa of Shadowed Boughs’s Static ability reads:
“Landfall: This support gains 1 shield.”
Nissa of Shadowed Boughs’s +1 ability reads:
“Target creature you control gets +3/+3 and gains Menace until end of turn. Then, convert 3 gems to that creature’s colors.”
One ability is not dependent of the other. However, if you use this vanguard’s +1 ability you cannot use it ever again until a Landform happens (it can be yours or your opponent’s but it has to be a landform). To make it more weird, if you use the +1 ability and then you match 5 gems during your turn, since 5 gems count as a landform you can use the +1 ability again in the extra turn granted by the 5 match you previously made.
You can watch all those interactions in the following video: