How does topping damage trees?

How does topping damage trees?

Topping occurs when the vertical stem (leader) and upper primary limbs (scaffold branches) on mature trees are cut back to stubs at uniform height. Topping is also referred to as heading, stubbing, or dehorning.
1) Topping reduces food-making capacity. Trees require a large leaf surface area to provide food for maintenance and growth. Topping cuts off a major portion of the tree's food making potential and depletes the tree's stored reserves.
2) Topping stimulates undesirable "water sprout" growth. While removing most of the buds that would form a normal branch system, topping often stimulates the regrowth of dense, unattractive, upright branches (water sprouts) just below the pruning cut. Water sprout regrowth is vigorous. A topped tree will rapidly return to its original height, but will lack its original form

3) Topping leaves large wounds. The branch wounds left from topping are slow to close, therefore more vulnerable to insect attacks and fungal decay. An invasion by either pest can spread into the trunk, killing the tree.
4) Topping creates a hazard. Weakened stubs are more prone to wind and storm breakage because they generally begin to die back or decay.
S) Topping injures bark. Increased sun exposure on trunk and branches can lead to severe bark damage.

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