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 of time. 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.
Occurrence
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. Primary succession leads to conditions nearer optimum for vascular plant growth; pedogenesis or the formation of soil, and the increased amount of shade are the most important processes. These pioneer lichen, algae, and fungi are then dominated and often replaced by plants better adapted to less harsh conditions, these plants include vascular plants like grasses and some shrubs that are able to live in thin soils that are often mineral based. Water and nutrient levels increase with the amount of succession exhibited. The early stages of primary succession are dominated by species with small propagules which can be dispersed long distances. The early colonizers—often algae, fungi, and lichens—stabilize the substrate. Nitrogen supplies are limited in new soils, and nitrogen-fixing species tend to play an important role early in primary succession. Unlike in primary succession, the species that dominate secondary succession, are usually present from the start of the process, often in the soil seed bank. In some systems the successional pathways are fairly consistent, and thus, are easy to predict. In others, there are many possible pathways. For example, nitrogen-fixing legumes alter successional trajectories. Spores of lichen or fungus, being the pioneer species, are spread onto a land of rocks. Then, the rocks are broken down into smaller particles. Organic matter gradually accumulates, favoring the growth of herbaceous plants like grass, ferns and herbs. These plants further improve the habitat by creating more organic matter when they die, and providing habitats for insects and other small animals. This leads to the occurrence of larger vascular plants like shrubs, or trees. More animals are then attracted to the area and a climax community is reached.
Examples
One good example of primary succession takes place after a volcano has erupted. The lava flowsinto the ocean and hardens into new land. The resulting barren land is first colonized by pioneer organisms, like algae, which pave the way for later, less hardy plants, such as hardwood trees, by facilitating pedogenesis, especially through the biotic acceleration of weathering and the addition of organic debris to the surface regolith. An example of this is the island of Surtsey, which is an island formed in 1963 after a volcanic eruption from beneath the sea. Surtsey is off the South coast of Iceland and is being monitored to observe primary succession in progress. About thirty species of plant had become established by 2008 and more species continue to arrive, at a typical rate of roughly 2–5 new species per year. Another example takes place after a glacier in Signy Island, South Orkney Islands, Maritime Antarctic. Glacier retreat is becoming more normal with the warming climate, and lichens and mosses are the first colonizers. The study, conducted by Favero-Longo et al. found that lichen species diversity varies based on the environmental conditions of the previously existing earth that is first exposed and the lichens reproductive patterns.
