Seen it. This is because the bag contains nutrients, such as nitrogen, phosphorus, potassium and other inorganic nutrients that big trees need. Because the roots of big trees can only absorb water, inorganic salts and other inorganic substances (can only rely on leaves to replenish organic matter), once the roots are damaged, they can only rely on external forces to transfer organic matter to the conductive tissue of the tree, just like human beings. It's like an infusion, injecting nutrients into the tube to keep the tree alive. Of course, it is also possible that there are not enough nutrients in the soil, so some supplementary treatments are required.
I hope this can answer your questions~