EVERYDAY SCIENCE

Detailed explanation-1: -Lichens that colonize bare rock secrete acids that break down the rock and start the soil-production process. Also, as lichens die, they provide some organic matter that also contributes to soil. Mosses can then colonize the thin soil; as mosses die, the soil thickens more allowing other hardy species to colonize.

Detailed explanation-2: -The first species to colonize bare rock are usually lichens. In primary succession, they are thus the pioneer organisms. Before they can colonize an environment, many organisms need soil. Acids that break down the rock and start the process of soil formation are secreted by lichens that colonize bare rock.

Detailed explanation-3: -Lichen hyphae dissolve rock by producing weak acids, depsides and depsidones, and by releasing carbonic acid, a byproduct of normal metabolism and a stronger acid. Carbonic acid dissolves calcium carbonate, a major constituent of limestone and the predominant cementing matrix of some types of sandstone.

Detailed explanation-4: -Lichens have been nicknamed “natures pioneer” because they can colonize bare rock and are usually first to establish on newly exposed surfaces.

Detailed explanation-5: -One ecological pioneer that grows on bare rock is lichen-a mutualistic symbiosis between a fungus and an alga. Over time, lichens convert, or fix, atmospheric nitrogen into useful forms for other organisms, break down rock, and add organic material to form soil. Certain grasses are also pioneer species.