Describe the process of primary succession

Primary succession is the change in an ecosystem from bare ground to a stable, complex ecosystem. Pioneer species are the first to colonise this bare ground, with adaptations to the harsh, low-nutrient conditions that may include deep root systems, such as Maram grass, or symbiotic relationships, as in lichen, to obtain all the nutrients they require. The presence of these pioneer species increases the organic content of the substrate, facilitating the secondary colonisation, often by grasses, mosses or other fast-growing species. These species introduce yet more organic matter, developing soils that allow the successive colonisation of shrubs, then trees which may develop into a complex, stable climax community.