What is the names for plants that survive a major disturbance?

The eruption of Mt. St. Helens is considered to be one of the worst destructions that is ever recorded in the United States. The entire seemed to have become a barren and lifeless space however, there are still a few plants who survived from the hot rocks coming from the volcanoes. These plants are called willow, vine maple, and black cottonwood. These plants were considered survivors for they had managed to re-sprout from the slightly wet area after the eruption. They became the pioneering life in reconstructing and reforming the landscape of the area.

I’m not really sure

A- a reduction in biodiversity