Lichens help in soil formation on bare rocks primarily through physical and chemical weathering, and by adding organic matter when they die. They colonize bare rock, secrete acids that break down the rock into smaller pieces, and extract minerals, creating crevices where a thin layer of soil can accumulate. When lichens die, their organic matter contributes to the soil, further enriching the developing soil layer and supporting other organisms.
Here’s a more detailed explanation:
Physical Weathering:
Lichens, as they grow, exert pressure on the rock surface, creating cracks and fissures. This physical stress, combined with expansion and contraction due to temperature changes and moisture, gradually breaks down the rock into smaller particles.
Chemical Weathering:
Lichens secrete acids, which chemically react with the rock minerals, dissolving and weakening them. This process further contributes to the breakdown of the rock into smaller particles.
Organic Matter Contribution:
When lichens die, their organic matter decomposes and mixes with the sediment from the fragmented rocks. This organic matter provides essential nutrients and improves the soil’s structure and water-holding capacity.
Mineral Extraction:
Lichens can also absorb minerals from the rock, further enriching the developing soil layer.
Creating a Suitable Environment:
The initial soil formation created by lichens provides a foundation for other organisms, like mosses and eventually larger plants, to colonize and further contribute to soil development.