Answer: Option B
:
B
For the initiation of ecological succession on a bare rock requires a pioneer organism like lichens which can facilitate suitable environment for the successve colonisation of other organisms.The acidic secretions from the lichens break down the the substrate and add to the accumulation of soil. Mosses then colonize the soil, adding enough nutrients in the soil for alder shrubs to take hold. Over maybe a hundred years, alders build up the soil nitrogen levels until spruces are able to thrive, eventually crowding out the alder and forming a dense spruce forest.Lichens are not only found as pioneer species but can also luxuriently grow on the barks or any other moist areas throughout the world. Since the tropics are relatively more humid, lichens grow luxuriently in the tropical regions.