Give scientific reasons: Lichens play an important role in biological succession and soil formation.

(N/A) $\rightarrow$ Lichens growing on rocks secrete organic acids,such as oxalic acid.
These acids penetrate the rock surface and create numerous crevices.
Dust and organic matter accumulate within these crevices.
Moss spores are then able to germinate and grow in these crevices,initiating the process of biological succession and contributing to soil formation.