Corrupted Roots — ruling 1

Corrupted Roots can enchant only a Forest or a Plains. It checks the enchanted land’s subtypes, not its name. If at any time the enchanted land is neither a Forest nor a Plains (due to Unstable Frontier’s ability, perhaps), Corrupted Roots is put into its owner’s graveyard as a state-based action.

Corrupted Roots — ruling 2

Corrupted Roots doesn’t care why the enchanted land becomes tapped. If that land changes from being untapped to being tapped for any reason, the ability will trigger.

Corrupted Roots : règles, fonctionnement et interactions (MTG)

Corrupted Roots is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Enchant Forest or Plains Whenever enchanted land becomes tapped, its controller loses 2 life.

How it works : Corrupted Roots

Original English text — Wizards of the Coast / Scryfall

#1February 1, 2009· Wizards of the Coast
Corrupted Roots can enchant only a Forest or a Plains. It checks the enchanted land’s subtypes, not its name. If at any time the enchanted land is neither a Forest nor a Plains (due to Unstable Frontier’s ability, perhaps), Corrupted Roots is put into its owner’s graveyard as a state-based action.
No other card is named in this ruling.
#2February 1, 2009· Wizards of the Coast
Corrupted Roots doesn’t care why the enchanted land becomes tapped. If that land changes from being untapped to being tapped for any reason, the ability will trigger.
No other card is named in this ruling.