8 junio, 2024

Dry forest: characteristics, flora, fauna, climate, relief

What is the dry forest?

The dry jungle The dry forest is a plant formation with a predominance of the tree biotype in a subtropical and tropical lowland climate. This jungle is characterized by presenting a prolonged warm dry season that occurs in the period corresponding to the astronomical winter.

It is one of the most threatened biomes, since it generally occupies the most suitable areas for the establishment of human settlements. In addition, it has land suitable for agriculture and livestock and has been a traditional source of wood and firewood.

It is currently estimated that there are about one million square kilometers of tropical dry forest worldwide. Of this extension, around 54% is in South America.

What determines the formation of dry forests is the climate and the soil, in addition to a dry season that lasts from 3 to 5 or more months in winter. The soils are of medium fertility, with no major restrictions on radical development.

Characteristics of the dry forest

The dry forest or dry forest is a biome of the tropics and subtropics in lowlands with a biseasonal climate.

– Plant structure

The dry forests have a less complex structure than the tropical humid forest, with less strata and less epiphytism and climbing. In general, there are two to three layers, including an understory of herbs and shrubs that can range from sparse to dense.

Another characteristic of dry forests is that the height of the trees is much lower than in the case of the rain forest. Their size ranges from 6 to 12 meters, although in semi-deciduous forests they can reach heights of 30-50 m.

– Adaptive strategies

In jungles or dry forests, the limiting factor is water, which forces the vegetation to develop strategies to survive. These strategies revolve around the need to maximize efficiency in the use of water and can be isolated or combined.

foliar expiration

One way to reduce water loss in the dry season is by shedding the foliage, since plants transpire through the leaves. However, this is not without drawbacks, since these are the productive organs of the plant.

When losing the leaves, the plant needs to enter a state of decreased metabolism to save as much energy as possible (dormant). On the other hand, when the rainy season arrives again, they must use a large amount of energy and matter to form new foliage.

Some deciduous or deciduous species are the ceiba (kapok pentandra) in America and teak (tectona grandis) in Asia.

phreatophytes

Some species of dry forest plants are evergreen, keeping their leaves even in the dry period. They do this because they have a deep root system that allows them to access groundwater at great depths.

Species with this strategy are known as phreatophyte plants, such as the Cumaná olive tree (Capparis odoratissima).

reserve structures

Another strategy in dry forests is the development of water reserve structures, either in stems or in roots. Cacti, for example, store water in their succulent stems, which have mucilages that favor water retention.

On the other hand, there are plants that develop lignified roots capable of storing water, called xilopódios.

sclerophyll

One way to reduce water loss through transpiration is to reduce the size of the leaves and reinforce them with stiff tissue (sclerenchyma).

Leaf blade reduction

In other cases it is not the total size of the leaf that is reduced, but the leaf area exposed to solar radiation. Here it is a matter of developing a compound leaf, that is, a leaf blade finely divided into leaflets or pinnae.

– Types of jungles or dry forests

Depending on the severity of the dry period, the type of soil and the characteristics of the water table, different types of jungle or dry forest are generated.

Jungle or spinescent xerophytic forest (Espinal or spinar)

In these dry forests, the strategies of leaf reduction, sclerophyll and succulence predominate. Most species are evergreen, but with very finely divided compound leaves.

Strategies based on the transformation of leaves into thorns and succulent photosynthetic stems are also presented. These jungles or spiny forests are found in various areas of South America, continental Africa, and in Madagascar.

In general, thorny plant species abound, which is why they are called spinal (Argentina) or spinal (Northern South America).

Jungles or deciduous forests

Here the dry season is long, lasting 5 or more months, and they are characterized by being forests where more than 80% of the individuals lose all their foliage in the dry season. They can also occur in areas with a shorter dry period, but with mountainous relief.

In the latter case, the steep slopes combined with a predominantly sandy soil reduces water retention.

Jungles or semi-deciduous forests

In these forests at least 50% of the individuals present are evergreen, maintaining foliage in the dry season. The dry season can last between 3 and 4 months or have groundwater sources.

Jungle or monsoon forest

It is a type of dry seasonal forest, similar to the semi-deciduous forest but with a greater structural development. They are similar in complexity to the tropical rain forest, with greater climbing and epiphytism.

– Floor

Sandy, sandy loam or clay loam soils predominate, with medium fertility and moderate pH. Due to the fact that rainfall is not very intense, these soils have low nutrient losses due to leaching or washing.

Forests cannot be established on shallow soils or with lateritic layers that limit root penetration.

– Location

Jungles or dry forests are present in tropical and subtropical regions of both hemispheres, dominated by trade winds or monsoons.

America

In the American continent, the dry forest is located from the north of the Yucatan Peninsula (Mexico), Central America, to South America.

In this area there is a dry forest on the Caribbean coast and in the Colombian-Venezuelan plains. Similarly, on the Pacific coast of Ecuador and Peru and in the north of Argentina, in Paraguay and south and east of Brazil.

The largest extensions of dry forests continuously occur in Bolivia and Brazil (Caatinga and Cerrado).

Africa

The dry forest extends from the west-central Atlantic coast and runs between the sub-Saharan savannah to the north and the rain forest to the south. It then continues through the Rift Valley south to Namibia and expands into the African Plateau.

In this area it reaches the southeast coast, with enclaves in Ethiopia, Somalia, Kenya, Tanzania, Mozambique and Zimbabwe up to the island of Madagascar. Similarly, there are some areas of dry forest in Egypt to the northeast.

Indo-Asian and Australasian region

These are the typical monsoon climate jungles, with the seasonality determined by the monsoon winds. Dry forests are found in Pakistan and India as well as in Thailand, Laos, Cambodia, Vietnam and southeastern China and in northern and eastern Australia.

Flora of the dry forest

Jungles or dry forests are less biodiverse than humid tropical forests, even so, they have a large number of plant species. In some cases they are particularly rich in endemic species.

– Leguminosae or Fabaceae

The Leguminosae family is the most common in all dry forests worldwide. Among these, species of the mimosoidea group stand out, which are characterized, among other things, by having finely divided leaves.

In America

Species of the genera are common Acacia, Pithecellobium, prosopis, albiziaamong others.

In Africa

In the Zambian region, the mopane forest (Colophospermum mopane) an endemic legume. Mopane forests are low, with heights of 8 meters or less that include other legumes, mostly of the genus Acacia.

– Malvaceae

Also called Bombacaceae. Another characteristic group of plants are the bottle trees of the malvácea family, so called because they have a thickened, curved trunk (paquicaules). In America is the ceiba (kapok pentandra), while in Africa we find the baobab (Adansonia spp.) and in Australia the Brachychiton populneus.

– Monsoon forest

Teak (tectona grandis, Verbenaceae) and various species of bamboo (grasses of the Bambusoideae subfamily). Mango species are also characteristic (Mangifera spp.), neem (Azadirachta indica) and the mahua (mahua longifolia).

fauna of the dry forest

The thorny forests or spiny xerophilous forests do not harbor a very numerous fauna, due to their extreme temperature conditions and water deficit. However, in the deciduous forests and, even more so, in the semi-deciduous ones, the fauna is abundant.

– Mammals

In the dry forests of South America there are felines such as the jaguar (panthera onca), the Puma (puma concolor) and the ocelot (leopardus pardalis).

Primates such as the red howler monkey (Alouatta seniculus) and wild pigs such as the collared peccary (tajacu peccary). Likewise, the most numerous mammals are various species of bats and rodents.

mopane forest in africa

Elephants live here (loxodonta africana), giraffes (giraffa camelopardalis), black rhinos (Diceros bicornis) and whites (Ceratotherium simum) that feed on mopane. Likewise, it is possible to get warthog (Phacochoerus sp.) and different species of zebras (equus spp.).

Among the large predators are the lion (Panthera leo) and the leopard (Panthera pardus).

– Birds

Among the birds of the South American dry forests are the guacharaca (Ortalis ruficauda) and the turpial (icterus icterus). In Africa there are the ostrich (struthio camelus), various species of vultures (genera Torgos, Trigonoceps and gypsies) and the martial eagle (Polemaetus bellicosus).

– Reptiles

There are species of venomous snakes of the genus Bothrops and turtles like the morrocoy (Chelonoidis carbonaria).

Climate

Jungles or dry forests develop in bi-seasonal tropical climates with a marked and prolonged dry season. The maximum precipitation in these forests occurs in the summer period.

precipitation

Average rainfall is medium to high, varying between 600 mm and up to 2,000 mm. However, even if the rainfall is high, there is always a dry period of 3 to 5 months or more.

Temperature

In all types of dry forests, average temperatures are high, above 25ºC.

Relief

The dry forests occur in varied reliefs, from plains, intramontane valleys, plateaus and mountainous areas. They are located between sea level and a maximum height of 600 meters above sea level, below the orographic condensation zone.

In the mountainous areas to the leeward, dry forests can occur at higher altitudes (700-800 meters above sea level).

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