7 junio, 2024

Scrub: characteristics, relief, flora, climate, fauna, examples

He scrub It is a plant formation characterized by the predominance of shrubs and short trees. This term is applied to different ecosystems, both in temperate and tropical zones. It can be constituted by primary or mature vegetation, as well as being a secondary formation product of anthropic intervention.

Its structure may consist of a single layer of shrubs or present a lower tree layer and a second shrub layer. The limiting factor is the characteristic dry period of scrub areas.

Scrub plants have adapted in various ways, either losing their leaves in the dry season or becoming sclerophyllous. Another factor that affects its ecology is fire, whether due to natural fires or caused by humans. The soils generally have low fertility, being predominantly sandy and with variations in the geography of the scrub.

This plant formation is highly variable, but in all types of scrub the common factor is the predominance of the shrub biotype and stunted trees. Based on this, there are two general types which are the Mediterranean scrub and the tropical scrub.

The Mediterranean scrub is present on the coasts of the Mediterranean Sea basin, as well as the Chilean scrub, the Californian chaparral (USA), the South African fynbo, the Kwongan and the Australian mallee.

Within the tropics are warm-climate xerophytic shrublands and high-montane cold-climate shrublands. Among the first are the catinga, the arid chaco, the cardonal-espinar and the African scrub. The páramo shrubland or scrubland is an example of a cold-climate tropical scrubland in the high Andean mountains.

The bushes develop in very varied reliefs that go from sea level to 4,000 meters above sea level. These include plains, valleys, and rugged mountainous areas.

The flora varies depending on the geographical area and among the most common families are leguminous, ericaceous, myrtaceae and composite. Among the species, the wild olive tree stands out (olea europaea var. yesylvestris) in the Mediterranean Sea basin and cacti in the warm tropical scrublands.

The main climates in which the scrub develops are the Mediterranean, the warm tropical and the cold tropical high mountains.

The fauna that inhabits the different types of scrub is equally varied, since you can find small mammals such as the Cretan spiny mouse (Acomys minous) in the Mediterranean, as well as elephants (Loxodonta africana) in the African bushlands.

Shrublands are not very productive ecosystems, but they have traditionally helped meet the needs of nearby communities. In them agricultural, livestock and tourist activities are carried out, in addition to extracting raw materials.

Within these plant formations there are protected areas. For example, the Cabo de Gata-Níjar Natural Park (Spain) and the Sus-Masa National Park (Morocco), representatives of the Mediterranean scrub. The Baviaanskloof Mega Reserve (South Africa) is an example of fynbos and the Mucubají Lagoon in the Sierra Nevada National Park (Venezuela) includes paramero scrub.

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General characteristics

– Origin

primary scrub

The scrub originates as primary or mature vegetation in environments with certain limitations for plant development.

In some cases there is a sufficient supply of water, but the limiting factor is the soil. Note that there may be soils that may be particularly alkaline, saline or rich in some particular element (eg aluminum).

For other scrublands, the limitation is given by extreme temperatures, combined with dry winds (cold or warm).

secondary scrub

They are areas of degraded forests, either by natural phenomena or by anthropic action. Among the natural causes are fires (of natural origin), landslides and landslides.

Anthropic causes include human-caused fires and deforestation.

In any case, the primary vegetation cover of the forest (trees, shrubs and grasses) are removed from the area. Given this, a natural recovery process begins, as long as the disturbing action ceases.

During the process of natural succession, thickets are initially formed, which can then continue to advance until the forest is established again. However, in some cases the secondary scrub persists as the definitive vegetation.

The latter happens when the disturbance generated irreversibly affects the environmental balance that allows the existence of the forest.

– The vegetation and its structure

The vegetation of the scrub is sclerophyllous evergreen in the scrub of temperate and cold zones and deciduous in the warm scrub.

An evergreen plant is one that keeps its leaves throughout the year, while deciduous plants lose their leaves in the dry season. Sclerophyllous species have small, rigid leaves with abundant sclerenchyma tissue (lignin).

This type of vegetation tends to be dense, making it difficult for large animals and humans to move around. In addition, it is common for plant species to be thorny in different parts of their body.

tall thicket

It has a vegetal structure characterized by the abundance of shrubs and low trees. A shrub is a woody plant at least in its lower part, branched at the base, with a maximum height of 4-5 m.

The typical stunted trees of the scrub do not exceed approximately 6-8 m. Therefore, the upper layer of the scrub reaches between 4 and 8 m in height up to 10 m in the Australian mallee.

The scrub can have a middle layer of shrubs of intermediate size between 1 and 2 m in height. In the lower stratum, herbs and subshrubs are located discontinuously covering the soil.

Medium and low scrub

There are scrubs that develop in more extreme environmental conditions, made up of low-growing shrubs and subshrubs. In this case the structure is much simpler, similar to that of a grassland, with practically a single layer.

The height of these scrubs ranges from 30-70 cm to 1-2 m, as in the case of the English heaths and also some Andean scrub.

– Fire and scrub vegetation

In most scrubland ecoregions, fire is identified as a modeling factor. In this vegetal formation, species adapted to survive before the action of periodic fires predominate.

Fires can occur due to natural causes or due to human action (anthropic causes). They cause periodic processes of plant succession, which is why the species present vary.

adaptations

Among the adaptations of the plants are the underground structures that allow the regrowth after the burning of the aerial part. Likewise, the presence of suberified barks (with cork) is common to resist both drought and the action of fire.

– Soil

It is generally poor, with predominantly sandy to loamy-sandy soils with an abundance of stones. They are generally permeable soils with medium to low moisture retention or with limitations due to alkalinity, acidity or salinity.

However, given the geographical variability of the scrubland, clayey soils and other types can be found. Thus, in the fynbos (South African scrub) there are complex mosaics of soils in its area of ​​distribution.

The scrub is a category referring to a wide series of plant formations whose common element is the predominance of shrubs. In this sense, there are many types, applying local names in each region.

Mediterranean scrub

According to its geographical location and its species composition, at least 5 subtypes of Mediterranean scrub are identified:

Shrubland of the coast of the Mediterranean Sea

It develops along the entire northern coast of the Mediterranean Sea from the Iberian Peninsula to the Middle East. The plant formation reaches its greatest development to the west of the African Mediterranean coast.

The Mediterranean scrub receives different names such as maquis or maquis (Italy, France), garrigue (France), phrygana (Greece), batha (Israel) and tomillar (Spain).

Some of the terms used to refer to the Mediterranean coast scrub refer to particular characteristics. For example, the garrigue is a Mediterranean scrub of secondary origin, since it comes from the degradation of the chaparral.

Chilean scrub (Chile)

These are Mediterranean scrublands and thorns located on the coast and the Central Valley of Chile (Pacific Ocean). In the Cordillera de la Costa they are to the west, between 400 and 1,000 meters above sea level.

They are bordered to the east by the Andes Mountains, to the north by the Atacama Desert, and to the south by the temperate rain forest.

Californian Chaparral and the Coastal Sage Scrub

Located in the United States and Mexico. The term chaparral comes from the Basque (txaparro) and designates the oak or holm oak with its low biotype. The chaparral extends through the center and south of the state of California, both in valley areas and in low mountains.

This is a thicket of small trees and shrubs, which reaches a height between 3 and 5 m. In some coastal areas of California, low scrub occurs with a predominance of shrubs of the genus Sage of the family Lamiaceae.

The fynbos (South Africa)

It is the most widespread plant formation in the Cape Town area of ​​South Africa, an area very rich in flora. It consists of a dense thicket made up of low-growing shrubs, in which different associations can be distinguished.

The associations depend on the group of predominant species and develop from sea level to 2,000 meters above sea level.

In the transition zone to the temperate forest is the fynbos-Virgilia divaricata, an association between the fynbos and elements of the forest. In this stands out the arboreal species Virgilia divaricata.

The Kwongan and the Mallee (Australia)

The kwongan is a low thicket of sclerophyllous shrubs (leaves tough from sclerenchymal tissue) that extends across the south-west of Western Australia. For its part, the mallee corresponds to eucalyptus thickets located in southern Australia.

– Heather

This plant formation is characterized by the presence of small shrubs up to 3 m high called heather (different species of the genus Erica).

Heaths are characteristic of the Mediterranean Sea coast and fynbos, but can also be found in other places such as Central Europe (Lüneburg Heath or Moorland, Germany) and England (New Forest Heaths).

– Warm xeric scrub

catinga

It is a warm dry scrub or chaparral located in northeastern Brazil, made up of shrubs and stunted trees. It is formed by deciduous plants that in many cases are thorny.

It develops in a bi-seasonal climate, with a wet season from February to May and a dry season the rest of the year. Average temperatures are around 24 to 26 ºC throughout the year, with rainfall of 500 to 700 mm.

arid chaco

It covers extensive plains and mountains of central-western South America, occupying areas of Bolivia, Paraguay and Argentina.

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