Why would you wrap plastic film in a tree?
If it is small plastic into sterilized soil or sand, wrapped in plastic parts can give birth to the root, the part of the plastic bag cut produces a new plant (this propagation method called "Air Layering Method)
Wrapped plastic is to keep moisture, in order to prevent evaporation of water and die plants, and afraid of the wound fungal infection.
A thin layer of skin is first cut and then wrapped in plastic film. In Botany, it is called "ring cutting". It is a kind of control technique and can also control the growth of plants.
