Abandoned railroad tracks are overgrown with weeds. ten years later there are small aspen trees growing in the middle of the tracks. this change is an example of

This change is an example of ecological succession
Ecological succession is a process that makes an ecosystem gradually changes overtime, including all organisms that took part in that ecosystem.
Ecological succession could change the dominant player that played a major role in that specific ecosystem.

Isay b but i'm not sure.