How does spruce affect other trees in the forest?

Spruce is a coniferous shade-loving tree. At the beginning of their life, young spruces grow well in the shade of deciduous trees or pines, since they cannot stand direct sunlight. But, in an old spruce forest, their pyramidal dense crown makes it impossible to grow trees that need a lot of light. As the spruce grows, light-loving deciduous trees and pines, which also need a lot of light, are displaced. This is one of the clearest examples of the struggle for existence in the plant kingdom.