On an area of 10 square meters. meters from 700-900 young fir trees after 20 years, 2-3 spruce remains

On an area of 10 square meters. meters from 700-900 young fir trees after 20 years, 2-3 spruce remains. What are the reasons for the decrease in the number and biological significance of this phenomenon?

1) Causes of death: competition between intraspecific and interspecific, eating by animals, damage by parasites, adverse climatic conditions.
2) Biological significance: the “excess” of offspring insures the species from extinction,
3) the individuals most adapted to these conditions remain.

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