Title: Forestspirit, Forestspirit
Author: Bogi Takacs
Published: Clarkesworld, June 2015: http://clarkesworldmagazine.com/takacs_06_15/
Description, by Sam Tomaino [SFRevu]: "Forestspirit is actually alien technology, left behind, that can take many forms. He meets Peter, a human boy, who tells him the group called the Consentience means to destroy the forest. What can they do to stop them?"