Secondary succession is generally faster because soil, nutrients, propagules, decomposer communities, and sometimes resprouting plants survive the disturbance. Primary succession must begin with substrate weathering and soil formation, processes that can delay the establishment of larger and more resource-demanding species for decades or centuries. Successional trajectories emerge from dispersal, establishment, species interactions, and organism-driven environmental change. Priority effects can make arrival order important, while retained soil and propagules strongly accelerate recovery after
Ref:
Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 20