<Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> Primary succession is one of two types of biological and ecological succession of plant life, occurring in an environment in which new substrate devoid of vegetation and other organisms usually lacking soil, such as a lava flow or area left from retreated glacier, is deposited . In other words, it is the gradual growth of an ecosystem over a longer period . </P> <P> In contrast, secondary succession occurs on substrate that previously supported vegetation before an ecological disturbance from smaller things like floods, hurricanes, tornadoes, and fires which destroyed the plant life . </P> <P> In primary succession pioneer species like lichen, algae and fungi as well as other abiotic factors like wind and water start to "normalize" the habitat . Primary succession begins on rock formations, such as volcanoes or mountains, or in a place with no organisms or soil . This creates conditions nearer optimum for vascular plant growth; pedogenesis or the formation of soil is the most important process . </P>

Where does brown soil come from in primary succession