Although a girdled (upto bast) tree may survive for sometime, but it eventually dies because:
A girdled (up to bast) tree may survive for some time, but it eventually dies because sugar and other organic solutes will not move downwards.
Girdling experiment is used to identify the tissue through which the food is transported. In this experiment, a ring of bark (phloem) is removed from the wood by a technique known as girdling. Since the woody xylem part present on inner side remains intact, water and nutrient reach the leaves. After the preparation of the sugar and organic solutes by photosynthesis in the leaves, it is not transported to other parts below the girdle since the phloem part is removed. So it is observed that there is no transport of the food/sugar just below the girdle region and hence will die after some time. This experiment shows that the phloem tissue aids food transport.