Question

primary succession
the first species to start the successional process can erode rock into soil. what do we call these species?
pioneer species
climax species

Explanation:

In ecological succession, pioneer species are the first to colonize a barren environment (like bare rock) and start processes like soil formation. Climax species are part of the final stable community. So the first species in primary succession that erode rock into soil are pioneer species.

Answer:

Pioneer species