AP BIOLOGY

Detailed explanation-1: -Lichens contribute to soil formation by decomposition as well. There are two primary types of decomposition that contribute to the formation of soil: in-situ decomposition and litterfall.

Detailed explanation-2: -Parent materials Soil minerals form the basis of soil. They are produced from rocks (parent material) through the processes of weathering and natural erosion. Water, wind, temperature change, gravity, chemical interaction, living organisms and pressure differences all help break down parent material.

Detailed explanation-3: -One can encounter lichen on a barren rock face and over time find fertility in its wake. Foliose lichen expands when wet-attaching itself tightly to the rock-and then contracts when dry, which causes miniscule flakes of the rock to break off. And so begins a process of soil formation.

Detailed explanation-4: -Lichens growing on rocks secrete organic acids like oxalic acid. The acids enter the rock and produce a number of honey comb-like small crevices. <br> 2. Moss spores are able to grow over such crevices and start the process of succession and soil formation.

Detailed explanation-5: -Lichens are considered as pioneer species in primary succession on rocks because they can easily grow on rocks where other plants cannot grow. They produce oxalic acid which induced the weathering of rocks and thus soil is formed.