The thorn forest It is a plant formation with a tropical to dry subtropical environment, dominated by thorny trees. They are forests of little complex structure with an open and low canopy and one or two floors of vegetation..
They are located in a fragmentary way throughout the tropical strip in latitudes far from the equator, being found in America, Africa, Asia and Oceania. This type of forest belongs to the group of tropical dry forests that develop in bi-seasonal climates..
The thorn forests are characterized by high annual average temperatures and low rainfall concentrated in one period of the year, although there are thorn forests of high mountain dry valleys with low temperatures, for example in the Andean valleys.
The thorn forest shows a medium to low biodiversity, dominating plant families such as legumes and bignoniaceae, euphorbiaceae, burseráceas and malvaceae. While insects, reptiles and birds predominate in the fauna, mammals are also found.
These thorny forests have relevant natural resources, as they include medicinal plants and endemic species, as well as soils of medium and high fertility, and combustible material..
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Under the denomination of thorny forests, a variety of different plant formations are grouped in species composition. Its main characteristics being the dominance of armed plants (with thorns), its short size and the bi-seasonal climate..
These forests fall into the most general category of tropical dry forests, given the climate in which they develop and the water deficit they face, as well as the fact that they are located in the intertropical strip..
The thorn forest is characterized by presenting from one to two layers or floors of deciduous or evergreen trees, reaching its canopy low height (5 and 15 m high). May or may not have a lower level of tall shrubs and then an understory of grass and low shrubs.
In any case, the light penetrates especially in the dry season, when the plants lose their leaves or when they pass through the crowns of finely divided leaves. This, together with the high incident solar radiation, makes the forest floor receive great illumination..
Given these characteristics, it is important to take into account that thorn forests overlap with so-called thorn bushes. The latter in many cases are degraded expressions of the former and differ basically by height.
The thorny bushes do not exceed 5 to 7 meters in height. Therefore, sometimes a formation can be called thorn forest by one author and scrub by another..
Although they are in tropical areas, they have much less biodiversity than humid forests. However, there are many endemic or exclusive species, since their extreme conditions force the development of specific adaptations..
For example, the diversity of succulent plants, such as cacti in America and cactiform euphorbiaceae in Africa. While in the case of fauna, the diversity of reptiles is particularly relevant, given their adaptations to these dry and hot climates..
The main adaptation that the plants of these forests present are thorns, which can be leaves, stipules or leaflets or transformed stems. The central function of thorns is to protect plants from herbivores, since food is scarce in these dry areas.
On the other hand, if instead of leaves there are thorns, the plant reduces water losses and protects itself from herbivores at the same time. In this environment, the scarcity of water is the fundamental limitation and the leaves are the organs of transpiration of the plants..
When this happens, the photosynthesis function of the leaves is assumed by the stem, as it happens in most cacti. However, in most of the plant species of the thorny forest there are leaves and thorns.
In these cases the leaves, instead of a large and continuous leaf blade, are composed of small leaflets. In this way, photosynthesis can be carried out and minimize the loss of water through perspiration, while the spines provide protection..
Thorn forests develop in the area of tropical and subtropical dry forests or forests. This is generally between 20º and 10º latitude on both sides of the equator..
In America, thorn forests are found in Mexico from the subtropical zone in the north to the tropical zone in the south. They continue through Central America in a dispersed way along the coastal strips to the Caribbean coasts of Colombia and Venezuela in South America.
There are also thorn forests in some intramontane valleys and highlands of the tropical Andes, even above 2,000 meters above sea level..
They also extend through various islands of the Antilles and the Pacific coast from Colombia to Peru. Similarly, they are found in Bolivia, southeast and south of Brazil, and north of Argentina, Paraguay and Uruguay..
In this continent, thorn forests develop to the south, mainly in Zambia, Zimbabwe and Mozambique. As well as northwest of Madagascar, on some islands off the coast of Senegal northwest of the continent and north of the Sahara, in Morocco and Tunisia.
The highest proportion of thorn forest is found in India and mainland Southeast Asia. Some fragments also appear in Indonesia, Timor, New Caledonia and northeastern Australia.
The characteristic climate of the thorn forest is the tropical dry and warm with an annual average temperature is between 26 and 29ºC in the tropical zone. In subtropical forests it can be between 20 and 29ºC, being lower in high mountain thorny forests, where there are even night frosts..
On the other hand, rainfall is relatively low and concentrated in one period of the year, varying between 200 and 1,200 mm per year. In some cases the dry period covers half the year, although in others it lasts up to 11 months.
Relative humidity is low in these forests and nighttime temperatures tend to be cool. In addition, due to its tropical location, solar radiation is high throughout the year..
The thorn forest develops in the driest limit of the tropical dry forest. It is normally found in the life zone between arid or semi-arid areas and savanna.
In some valleys between high mountains in the Andes, small thorny forests develop. They are forests dominated by armed species and where the main limitation is water, although they vary in their temperature, which is much cooler and even freezes at night..
In the American thorn forests the most prominent elements of the flora are the cacti, an endemic family of this continent. Among them the tunas or nopales (Opuntia spp.) and cardones or candelabra type (Stenocereus griseus, Cereus exagonus and others).
Another relevant family are legumes, especially those belonging to the mimosas subfamily. An example is the species Prosopis juliflora, small armed and evergreen tree known as mesquite (Mexico), cují yaque (Venezuela) and tupillo (Colombia).
Similarly of legumes there are various species of the genus Acacia Y Pithecellobium. Another relevant genus of these forests is Haematoxylum, where is the Campeche stick (Haematoxylum campechianum).
In Mexico there are also abundant burseráceas species, especially of the genus Bursera, known as copal and palo mulato. The palo mulato, or the naked Indian, are also found in the thorny forests of northern South America, although with less diversity..
Legumes of the genus Acacia they are the most characteristic components of the flora of the African thorn forests. Similarly, the cactiform euphorbiaceae stand out, that is, similar to cacti, of the genus Euphorbia.
North of the Sahara, in Morocco and Tunisia there are small forests of Acacia tortilis. While in Madagascar the thorny bottle trees of the genus Pachypodium, from the apocinaceae family.
Small cats such as the ocelot (Leopardus pardalis) and the tigrillo (Leopardus tigrinus). Like foxesUrocyon cinereoargenteus), opossums (Didelphis spp.) and armadillos (family Dasypodidae).
In the thorny forests of Mexico and Central America, the coyote (Canis latrans). Another abundant group are reptiles, among which are rattlesnakes (Crotalus spp.).
As well as the green iguana (Iguana iguana). There is also a great diversity of birds, including the guacharaca (Ortalis ruficauda).
The thorn forests are a refuge for various species of gazelles and small mammals. While the striped jackal (Canis adustus).
The thorn forests of Madagascar are home to various species of lemurs (superfamily Lemuroides) and the island's largest predator, the fossa (Cryptoprocta ferox).
The thorny forest areas and the dry forest in general, present better health and access conditions than the humid areas. Because of this, they were traditionally selected for colonization by humans in America and Africa..
These forests provide combustible material in the form of firewood and charcoal, species of nutritional and medicinal value and fertile soil for agriculture and livestock. The only limitation is the availability of water, which has been resolved through wells, aqueducts and irrigation systems..
Due to these same characteristics, these lands have been considered suitable for extensive livestock farming, especially sheep and goats. Some species have industrial value, such as those of the genus Haematoxylon from which a dye is extracted.
Like others that provide tannins for leather tanning, such as the species of Prosopis.
In this country, the thorn forest occupies 5% of the territory, extending through the Pacific coastal plain in Sonora and southern Sinaloa, then continuing along the Pacific coast to the Isthmus of Tehuantepec and the Balsas depression..
While in the Gulf of Mexico it is dispersed in the coastal plain in Veracruz, San Luis de Potosí and Tamaulipas. While in the Yucatan Peninsula a type of thorn forest is found in the so-called "lowlands", which are depressions that are periodically flooded..
In the past, the thorn forest occupied a much larger area in Mexico, but since the 1940s it has been on the decline. This is due to the incorporation of land to agricultural production through the implementation of irrigation systems.
Mesquite aboundsProsopis juliflora), the Campeche stick (Haematoxylum campechianum) and the Sweet pithecellobium (guamúchil), ebony (Ebenopsis ebony) and the yellow paloverde (Cercidium microphyllum). Like numerous acacias (Acacia spp), copals and palo mulatos (Bursera spp.)
There is the coyote, the hares (Lepus spp.) and owlets (family Strigidae). The tlalcoyote or badger also inhabit here (Taxidea taxus) and the raccoon (Procyon lotor).
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