1. Lichens
2. Mosses
3. Grasses
4. Shrubs
5. Small Trees
6. Larger Trees
7. Herbaceous Plants
8. Mammals
9. Birds
10. Insects

Primary succession

Gradual growth and shift of an ecosystem into a new substrate
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Primary succession occurring over time. Soil depths increase in relation to increasing decomposition of organic matter. and there is a gradual increase in species diversity in the ecosystem. Labels I-VII represent the different stages of primary succession. I – bare rocks, II – pioneers (mosses, lichens, algae, fungi), III – annual herbaceous plants, IV – perennial and grassy herbaceous plants, V – shrubs, VI – shade intolerant trees, VII – shade tolerant trees.

primary succession in Rangitoto Island

primary succession is the initial stage of ecological succession after an extreme disturbance, which usually occurs in an environment devoid of vegetation and other organisms. These environments often lack soil, as disturbances such as lava flow or indentation glaciers Destroy the nutrient environment.

In contrast, secondary succession occurs on substrates that previously supported vegetation before a ecological disturbance. This occurs when minor disturbances such as floods, hurricanes, tornadoes and fires only destroy local plant life and leave nutrients in the soil for immediate establishment by intermediate species in the community.

Occurrence

In primary succession pioneer species like lichen, seaweed and fungus just as abiotic factors such as wind and water begin to “normalize” the habitat or, in other words, begin to develop the soil and other important mechanisms for greater diversity to flourish. Primary succession begins in rock formations, such as volcanoes or mountains, or in a place without organisms or soil. Primary succession leads to conditions closer to ideal for vascular plant growth; pedogenesis or soil formation and increasing the amount of shade are the most important processes.

These pioneer lichens, algae and fungi are then dominated and often replaced by plants better adapted to less severe conditions, these plants include vascular plants such as grasses and some bushes that are able to live in fine soils that are usually mineral based. Water and nutrient levels increase with the amount of succession displayed.

The early stages of primary succession are dominated by species with small propagules (seeds and spores) that can be dispersed over long distances. The first settlers – often seaweedfungus and lichens— stabilize the substrate. Nitrogen supplies are limited in new soils and nitrogen-fixing species tend to play an important role in the initiation of primary succession. In contrast to primary succession, the species that dominate secondary succession are usually present from the beginning of the process, often at the beginning of the process. soil seed bank. In some systems, successional paths are quite consistent and therefore easy to predict. In others, there are many possible paths. For example, nitrogen-fixing legumes alter successional trajectories.

spores of lichens or fungi, being the pioneer species, spread over a rocky terrain. Then the rocks are broken down into smaller particles. Organic matter gradually accumulates, favoring the growth of herbaceous plants such as Grass, ferns and herbs. These plants further enhance 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 greater vascular plants such as shrubs or trees. More animals are then drawn to the area and a climax community is reached.

species diversity it is also a major influence on the stages of succession, and as succession progresses, species diversity changes with it. For example, there is much less richness and uniformity of microorganisms in early successional stages, but late successional stage bacteria are much more uniform and rich. This again supports the hypothesis that as more resources are present in the later stages of succession, there are enough to support a more diverse ecosystem with many different reproductive strategies.

Examples

volcanism

An example of primary succession occurs after a volcano erupted. Lava flows into the ocean and hardens into new land. The resulting barren land is first colonized by pioneering organisms such as algae, which make way for less resistant later plants such as hardwood treesby facilitating pedogenesisespecially through 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 the sea floor. Surtsey is on the south coast of Iceland and is being monitored to observe ongoing primary succession. About thirty plant species became established in 2008 and more species continue to arrive, at a typical rate of approximately 2 to 5 new species per year.

A volcanic eruption occurred in Mount Saint Helena also, with primary succession initiated after the destruction of the region’s ecosystem. In the primary succession of Mount St. Helens, the region was heavily isolated. This type of incident causes the primary succession rate to be quite low, as many species that stand out in the establishment do not have the ability to effectively disperse in the new frontier. The opposite is also true, as species that were not very good at establishing themselves could not survive, even at high dispersal rates. The region has almost no organic materials to utilize, which was especially significant in Mount St. Helens, as its isolated location prevented the succession from taking place on the periphery of the destruction site. Initially effective ranged settlers are rare, as they are only truly effective after an initial settler has helped shift the region to more suitable conditions. This is why primary succession was slow in the destroyed region around Mount St. Helens.

Glacier Retreat

Another example is taking place in signy island in the Orkney Islands of South Antarctica, due to glacier retreat. Glacier retreat is becoming more normal with warmer weather, and lichens and mosses are early settlers. The study, conducted by Favero-Longo et al. found that the diversity of lichen species varies based on the environmental conditions of the previously existing land that is first exposed and the reproductive patterns of the lichens.

The characteristics of the succession

By analyzing a case study in Grand Bend, Ontario, a thorough understanding of the distinction between primary and secondary succession can be gained. The two species, Juniperus virginiana and Quercus prinoides, are reproducing rapidly and spreading grasses associated with primary succession on Grand Bend’s beach dunes. They are classified as selected species, with high mortality, rapid reproduction and a distinct ability to survive in harsh and nutrient-poor conditions. In contrast, ecological development after the completion of primary succession generally leads to a more strongly k-selected population, which has lower mortality and slower reproduction rates. In Grand Bend, this is demonstrated by the succession of oak and pine forests and the continued reduction of selected grasses. The temporal scale is also relevant, as the secondary succession of oak and pine forests occurs approximately 2,900 years after the initial cases of primary succession, while the end of dunes dominated exclusively by grasslands occurs approximately 1,600 years after the beginning of primary succession. This is extremely important, as it shows an intermittent period of 1,300 years in which primary succession is superseded by secondary succession. This period is likely characterized by high species diversity, a mix of selected species, and high community productivity. It is a well-accepted principle that an intermediate between ker-dominated populations leads to high productivity and species diversity, while secondary succession leads to climax communities with low species diversity. During this 1,300-year period, it is likely that resources grew to excess, which reduced species diversity, resulting in the oak and pine forest dominated by k.

It is very difficult to determine exactly which events will hinder or support the growth of a community, as the following example shows. Very few seedlings survive for a long period of time during primary succession, with 1.7% of seedlings in a floodplain called Skeiðarársandur in southeastern Iceland, lasting from 2005 to 2007. The rest have been replaced by new settlers, as mortality rates for selected species like these are extremely high. This is a very important phenomenon to watch out for, as even though population sizes may remain consistent throughout the history of a region, it is highly likely that many of the selected r organisms present are entirely new organisms. This is one of many highly unpredictable factors in the scale of ecological succession.

See too

References


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Search keywords List The Communities In A Successional Sequence Of Primary Succession

1. Pioneer species
2. Climax community
3. Abiotic factors
4. Ecological succession
5. Colonization
6. Lichens
7. Bare rock
8. Soil formation
9. Secondary succession
10. Successional stages
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