This is a complex question with a complex answer, but given the characteristic of a spruce forest, the answer can be simplified.
In a spruce monoculture, which is a man-planted forest usually following clear cutting, life is boring and monotone. Plant diversity is low, consequently fauna diversity is low as well in this artificial environment. The shapes, colours, sounds and smells are poor.
In a spruce forest with a natural and diverse structure, usually created by natural regeneration, life is interesting and diverse. Diversity of plant and animal species is high and there are many types of intraspecific and interspecific relations in this ecosystem. The shapes, colours, sounds and smells are diverse and challenging.
A virgin or semi-virgin spruce forest in the subalpine belt is vibrating of life with an apparent disorder and mixture of species, colours, shapes and ecological relations. On top of this, these forests are extremely stable. This is the goal in all of the Wildland owned forests, be it spruce forests or mixed forests further down.
This is why we aim to convert all monocultures to the diverse natural structure and to bring life from boring to wonderful.