DENDROLOGY

Detailed explanation-1: -Mosses and lichens are the first creatures to colonise rocks and thus have a significant ecological impact. They breakdown rocks, preparing the substrate for the growth of higher plants. Mosses decrease the impact of rain and prevent soil erosion by forming dense mats on the soil.

Detailed explanation-2: -In case of xerarch succession, lichens are the pioneer species. Lichen is a symbiotic association between a fungus and algae and/or cyanobacteria where both the organisms involved benefit from each other. Lichens secrete acids which dissolve rock and hence, help in weathering and soil formation during succession.

Detailed explanation-3: -Lichens grow very slowly and some lichens can live for several centuries. Lichens are pioneers: they have the ability to settle on substrates that are very low in nutrients and can withstand extreme temperature and light conditions. The first known lichens date back to the Devonian.