If you must prune in the summer, minimize the amount of wood and the quantity of leaves (pine needles) removed as these are the source of food for the tree and important to the ecology of the tree.
(you; must prune; T:in the summer) (the quantity of leaves; removed; as these) (these; are the source of; food)
you the quantity of leaves these
must prune removed are the source of
T:in the summer
as these
food