answer:I am not a tree expert, but here are some basics. I am not sure how sap stops “bleeding” when a tree is cut, but indeed trees can withstand cuts and even whole limbs being cut. When a tree loses too much sap it can lose it’s health and even die. Maple trees that are tapped for their sap to make maple syrup has to be done with care and not excessively. The owners watch the tree, and if it starts to show signs of becoming weak they will stop draining the tree of sap, maybe skip a year or two completely for that particular tree, so it can build back its health. Trimming trees back can help a tree gain new healthier growth. Limbs that are not doing well are a drain on the tree, as the tree still supplies nourishment to it. Cutting means the tree can give its resources to younger healthier growths. But, if a tree is cut back too much it cam go into shock and die.