Answer:
Competition.
Step-by-step explanation:
In this place a secondary succession occurs that happens in an environment that was previously occupied by other communities and that suffered some type of disturbance, in this case, the area was devastated by a volcanic eruption.
A secondary succession begins with the "nudation" phase which is the succession after a disturbance and the emergence of a site devoid of life. It continues with the "migration" that is the arrival of propagules to the environment.
Then comes the "ecese" which is the establishment and growth of the first pioneer plants. It continues with "competition" in which the establishment of new species causes competition for space, light and nutrients.