Which activity could trigger primary succession?

What are the headings of a data table

If scientists are wrong about earth's age based on radioactive material and the decay rates are really much faster, how would nuclear power plants be affected?

Legumes, a type of plant, require rhizobia, a type of soil bacteria, to survive since these organisms fix nitrogen during photosynthesis. rhizobia use the legumes for food. what would most likely happen to the legume population if rhizobia suddenly became extinct?