Magic Tree

The magic tree was a normal tree and lived in the forest, but one day a woodcutter came and started to cut down one tree after another. When the tree saw this, it tried to estimate the other trees, but it just couldn´t do it. Then a magician came to him and the tree asked him for help. The magician answered him that he must answer a question correctly...
Give me food and I will rise, give me water and I will go out. What am I? The tree thought for a long time, but then he called fire, the answer is fire. The mage nodded and handed him a crystal, then he disappeared. When the tree touched the crystal, it transformed. He now had legs and arms and from now on could protect his forest from the woodcutter.