What determines the duration of the existence of ecosystems? Why is the life of an oak forest

What determines the duration of the existence of ecosystems? Why is the life of an oak forest longer than the life of a mixed forest?

The lifespan of ecosystems depends primarily on the number of species that belong to that ecosystem. All of these species must be linked in different food chains. The more organisms and food webs, the more resilient the ecosystem is. The point is that some organisms can be interchangeable. Then their disappearance will not affect the entire system. Those forests where only one type of tree grows can exist longer, since there is only an intraspecific struggle between trees.