Tolerance model suggests:
The tolerance model allows early and late successional species to arrive independently; pioneers neither strongly facilitate nor inhibit later colonists. Species that tolerate lower resource levels or other conditions developing over time eventually persist and grow better, so their life-history traits drive replacement. A disturbance changes the availability of space, resources, and biological legacies, creating opportunities for colonization. Whether succession is primary or secondary depends chiefly on the starting substrate and survival of soil, not simply on the identity of the disturbanc
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 20