Answer:
Facilitation.
Step-by-step explanation:
The ecological succession is the various changes of the species and its ecosystem over the passage of time. The primary and secondary succession are two main types of ecological succession.
The facilitation model of succession explains that the former species makes environment more suitable for the up coming species. The later species require different niche and the former species makes the environment less suitable for itself but facilitate the growth of the later species.
Thus, the answer is facilitation.