Secondary Succession
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Secondary succession is the secondary
ecological succession Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire) or more or less. Bacteria allows for the cycling of nutrients such as ca ...
of a plant's life. As opposed to the first,
primary succession Primary succession is the beginning step of ecological succession after an extreme disturbance, which usually occurs in an environment devoid of vegetation and other organisms. These environments are typically lacking in soil, as disturbances l ...
, secondary succession is a process started by an event (e.g.
forest fire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
,
harvest Harvesting is the process of gathering a ripe crop from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper. On smaller farms with minimal mechanization, harvesting is the most labor-i ...
ing,
hurricane A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
, etc.) that reduces an already established
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
(e.g. a forest or a wheat field) to a smaller population of species, and as such secondary succession occurs on preexisting
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
whereas
primary succession Primary succession is the beginning step of ecological succession after an extreme disturbance, which usually occurs in an environment devoid of vegetation and other organisms. These environments are typically lacking in soil, as disturbances l ...
usually occurs in a place lacking soil. Many factors can affect secondary succession, such as trophic interaction, initial composition, and competition-colonization trade-offs. The factors that control the increase in abundance of a species during succession may be determined mainly by seed production and dispersal, micro climate; landscape structure (habitat patch size and distance to outside seed sources); bulk density, pH, and soil texture (sand and clay). Secondary succession is the ecological succession that occurs after the initial succession has been disrupted and some plants and animals still exist. It is usually faster than primary succession as soil is already present, and seeds,
root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
s, and the underground vegetative organs of plants may still survive in the soil.


Examples


Imperata

''Imperata'' grasslands are caused by human activities such as logging, forest clearing for shifting cultivation, agriculture and grazing, and also by frequent fires. The latter is a frequent result of human interference. However, when not maintained by frequent fires and human disturbances, they regenerate naturally and speedily to secondary young forest. The time of succession in ''Imperata'' grassland (for example in Samboja Lestari area), ''Imperata cylindrica'' has the highest coverage but it becomes less dominant from the fourth year onwards. While ''Imperata'' decreases, the percentage of shrubs and young trees clearly increases with time. In the burned plots, ''Melastoma malabathricum, Eupatorium inulaefolium, Ficus'' sp., and ''Vitex pinnata''. strongly increase with the age of regeneration, but these species are commonly found in the secondary forest. Soil properties change during secondary succession in Imperata grassland area. The effects of secondary succession on soil are strongest in the A-horizon (), where an increase in carbon stock, N, and C/N ratio, and a decrease in bulk density and pH are observed. Soil carbon stocks also increase upon secondary succession from ''Imperata'' grassland to secondary forest. Imperata ''Imperata'' is a small but widespread genus of tropical and subtropical grasses, commonly known as satintails. Satintail grass species are perennial rhizomatous herbs with solid, erect stems and silky inflorescences. The best known species is ...
''-dominated grassland"> File:Restoration.png File:Paku.jpg File:Vitex secondary.png


Oak and hickory forest

A classic example of secondary succession occurs in
oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
and
hickory Hickory is a common name for trees composing the genus ''Carya'', which includes around 18 species. Five or six species are native to China, Indochina, and India (Assam), as many as twelve are native to the United States, four are found in Mexi ...
forests cleared by wildfire. Wildfires will burn most vegetation and kill those animals unable to flee the area. Their nutrients, however, are returned to the ground in the form of ash. Thus, even when areas are devoid of life due to severe fires, the area will soon be ready for new life to take hold. Before the fire, the vegetation was dominated by tall trees with access to the major plant energy resource: sunlight. Their height gave them access to sunlight while also shading the ground and other low-lying species. After the fire, though, these trees are no longer dominant. Thus, the first plants to grow back are usually annual plants followed within a few years by quickly growing and spreading grasses and other pioneer species. Due to, at least in part, changes in the environment brought on by the growth of the grasses and other species, over many years, shrubs will emerge along with small pine, oak, and hickory trees. These organisms are called intermediate species. Eventually, over 150 years, the forest will reach its equilibrium point where species composition is no longer changing and resembles the community before the fire. This equilibrium state is referred to as the climax community, which will remain stable until the next disturbance.


Post-fire succession


Soil

Generation of carbonates from burnt plant material following fire disturbance causes an initial increase in soil pH that can affect the rate of secondary succession, as well as what types of organisms will be able to thrive. Soil composition prior to fire disturbance also influences secondary succession, both in rate and type of dominant species growth. For example, high sand concentration was found to increase the chances of primary ''Pteridium'' over ''Imperata'' growth in ''Imperata'' grassland. The byproducts of combustion have been shown to affect secondary succession by soil microorganisms. For example, certain fungal species such as ''Trichoderma polysporum'' and ''Penicillium janthinellum'' have a significantly decreased success rate in spore germination within fire-affected areas, reducing their ability to recolonize.


Vegetation

Vegetation structure is affected by fire. In some types of ecosystems this creates a process of renewal. Following a fire, early successional species disperse and establish first. This is followed by late-successional species. Species that are fire intolerant are those that are more flammable and are desolated by fire. More tolerant species are able to survive or disperse in the event of fire. The occurrence of fire leads to the establishment of deadwood and
snags In forest ecology, a snag refers to a standing, dead or dying tree, often missing a top or most of the smaller branches. In freshwater ecology it refers to trees, branches, and other pieces of naturally occurring wood found sunken in rivers and ...
in forests. This creates habitat and resources for a variety of species. Fire can act as a seed-dispersing stimulant. Many species require fire events to reproduce, disperse, and establish. For example, the
knobcone pine The knobcone pine, ''Pinus attenuata'' (also called ''Pinus tuberculata''), is a tree that grows in mild climates on poor soils. It ranges from the mountains of southern Oregon to Baja California with the greatest concentration in northern Calif ...
has closed cones that open for dispersal when exposed to heat caused by forest fires. It grows in clusters because of this limited method of seed dispersal. A tough fire resistant outer bark and lack of low branches help the knobcone pine survive fire with minimal damage.


References

{{reflist Ecological succession Forest ecology Habitat Environmental terminology