Why is the autumn color of leaves and leaf fall in different parts of the crown of the same

Why is the autumn color of leaves and leaf fall in different parts of the crown of the same tree observed at different times?

The leaves acquire an autumn color when the chlorophyll in them is destroyed, therefore other pigments with bright yellow and orange colors are unmasked (xanthophylls, carotenes). The plant, in preparation for hibernation, accumulates and redistributes nutrients. Therefore, yellowing and leaf litter are most rapidly observed in the shaded areas of the crown, which can no longer synthesize substances in conditions of decreasing illumination. The separating plate at the base of the petiole is finally formed only when there is nothing left in the leaf that would be useful to the plant in hibernation – that is why the leaves fall off so beautiful.