Bouncing Birch

The Bouncing Birch is a usually quadripedal, but also tripedal, quantipedal or hexapedal species of tree, which originates and is endemic to temperate boreal climates, from which it has escaped and managed to spread around the world, using its unique lower trunk and root structures which resemble the form of humanoid lower limbs. It is the result of a union between a shaman and their forest, which got too intense and went too far. Bouncing Birch trees are lean and reach a height comparable to yet less than that of their rooted relatives. They come in colour varieties of light browns and greys, usually shedding in horizontal stripes, which gives them their shaded patterns and texture. They get nutrition the same way as most plants, through sunlight, water, and minerals or other nutrients from the ground, but since they can move, they're extremely competitive about it. Small patches of lean green leaves have been observed to move into larger patches of other (usually shorter) tree populations, and completely take over in the space of a few months to a year. Even though they move slowly, and usually when there's little movement around them, Bouncing Birches have been spotted uprooting and making a run for it, in very dire situations, like a fire or a fire-ant outbreak; curiously not to save themselves from being cut down, although a lot of woodcutters have reported being whacked by something really hard, while working on Bouncing Birch regions. On almost all occasions this has happened without any witness, so the accounts have often be discredited as confusion, accidents, or the lie one says when caught flat on the ground of one's workplace, with their eyes closed and their boss towering over them. There have even been instances of woodcutters or lonely travellers disappearing in Bouncing Birch forests, which has earned them some infamy, and even persecution and population control in some regions.
Trivia: 

Bouncing Birch trees were widely mobilised to help rebuild the world after the Flame Days. This made them more ubiquitous and influencial too.

Bouncing Birch's interests are represented in Inter-Race Councils by the Koalas, which are in turn represented by Clan Radiant of the Arboreal Pixie Empire, which represent most of the endemic races in the forests covering the majority of the north-western parts of the world.