The tropical forest is one of the most interesting zones from a biodiversity of species point of view, of both plants and animals. Commonly known as jungle, its main characteristic is the abundant and dense vegetation it presents. It is absolutely green and it dominates the landscape year round, benefited by the constant presence of a great amount of precipitation.
Plants reach their greatest height and grow in the most in this tropical biome. Nearly 40% of all plant and animal species live within this type of biome, which enjoys warm temperatures year round, as well as constant precipitation and a constant reception of solar radiation, which, falls more vertically at these latitudes.
For its analysis, and the analysis of its forms of organization and plant and animal development, it is possible to organize it into vegetation stratums or layers. From the surface to the highest point the trees reach, we can distinguish different levels. The first is known as the forest floor or inferior stratum, where roots settle and a direct traffic point for larger animals as well.
Higher up, some bushes, young trees, ferns and other plants like tall grasses are found, the life of which is conditioned by the competition for light, which is mostly captured by the plants that are higher up, meaning the plants that make up the forest layer or canopy. This level is one of the most interesting regarding the development of life in tropical forests because it is one of the highest canopies in the world, where light, heat and food is abundant, therefore, the majority of organisms live here, especially all kinds of insects. It can be divided into inferior (where the lower trees are located) and the canopy as such, made up of dispersed treetops. There are also sectors where trees reach over 70 meters and are widely spaced apart, making up the emergent layer.
Types of tropical forest
Depending on the frequency of rains and the duration of the dry season, we can distinguish three types of tropical forest: rainforests, seasonal forests and dry forests.
The fact that their boundaries are not clearly defined must be pointed out. As in all biome, many are the factors that affect their formation, reason for which altitude, latitude and the presence of some air masses determine the appearance of certain features that distinguish these types of tropical forest.
Next, we show you the main characteristics of each of them. However, later we will analyze the ones that lead the tropical rainforest to be considered the prototype of tropical forests.
Rainforests
Tropical rainforests, also known as pluvial or equatorial forests, are located between 10° N and 10° S latitude. This totally conditions the life forms that develop in this area, because this zone of our planet receives the greatest amount of annual solar radiation, almost constantly during the twelve months of the year, It is also an area of continuous precipitation (due to the quick evaporation).
Generally, it has very high and constant temperatures; with an average of 27°C. Precipitation in this area is also abundant, presenting a great amount of rainfall almost permanently (the annual average goes from 2,000 to 4,000 millimeters per square meter).
It is also possible to identify three groups of tropical rainforest. The first is located in the Amazonian basin, in South America, commonly known as the tropical rainforest of the Amazons or Amazonian rainforest. The second one spans from the west of India and south of China, passing through Malaysia and the Island of Java (in Indonesia) up to New Guinea (area known as indomalaya), while the third group is located in eastern Africa, around the Gulf of New Guinea and though the interior to the Congo basin.
There are also highly enclosed sectors where this type of forest develops, like the eastern coast of Madagascar, a few of the Hawaiian islands and the eastern coast of Australia.
Tropical and subtropical seasonal forests.
Another type of tropical forest is made up of tropical and subtropical seasonal forests, also known as semi-perennial or semi-deciduous forests, because some of the trees renew their leaves.
Temperatures are warm all year, but unlike tropical rainforests, they present two well-marked seasons: a rainy one and a dry one. This last one has a variable duration, that goes from two to four months, causing a great amount of the trees from the top layer to shed their leaves during the dry season, while the ones located under this layer develop as normal.
Monsoon forests of central Asia are one of the clearest examples of this type of tropical association. In this place, vegetation is used to the constant heat and dry conditions (during the dry season), but they are also capable of withstanding the abundant rains of the more humid periods.
Dry forests
They have a dry season, which is directly affected by the latitude of the spot. This way, the farther south from the equator we are, the longer the dry season, which can last up to eight months.
The changes between one season and another are very noticeable. While both trees and bushes shed their leaves in the dry season, the first sprouts flower with the imminent arrival of the humid period and the ground is covered by a green cover.
The density of vegetation is far lower, the undergrowth is thick and tangled (due to the greater presence and gathering of sunlight) and the bark of the trees is much more resistant and wrinkly (it acts as a protection mechanism in case of fire).
Although most dry forests are located in Africa and some tropical islands, they also take up large portions of central South America and other areas in southeast Asia.
Vegetation of tropical forests
The vegetation of tropical rainforests (as we said, they are considered the prototype of tropical rainforests) is so exuberant it looks like thick tissue in which huge trees criss-cross each other, lianas hang from everywhere, there are huge ferns, some palms and other herbs that compete for a ray of sun.
An enormous plant curtain that not only surprises because of the great amount of species, but also because it serves as a home for unique organisms.
We only have t imagine that the plant diversity is so large in this type of forest that, in an area of 10 square kilometers it is easily possible to see nearly 1,500 species of flowering plants and up to 750 species of trees. Scientists are even finding new species to this day, and they are sure there are many left that have yet to be discovered.
Many of the trees that make up the tropical rainforest can measure from 45 to 70 meters, while some plants reach up to five meters. The canopy is thick and continuous, except in the parts where there are courses of water. The tree trunks of the trees present are generally clear-colored, straight and they have buttresses.
The latter are expansions of the tree trunk itself (flat and resistant) that serve as real anchors in order to hold the trees on to the weak soil that supports them.
The development of smaller plants is hindered by the thick canopy, which prevents the arrival of light to the lower levels. However, in some cases, plants reach heights that can exceed four meters. They are mostly always green with elongated leaves that end in pointy tips to eliminate the excess of water, increase transpiration and reduce the washing of nutrients.
In this area, the growth of epiphytes is also common, which are characterized for developing and growing over other plants to capture a greater amount of light. They live in trunks, branches and even tree leaves and bushes, and they generally do not harm the tree or bush that houses them.
Plant adaptations
Except for the emergent vegetation (the tallest trees that peak out), most of the trees, plants, herbs and bushes of tropical forests must compete for the light they need to survive.
This factor conditions all plant development, directly influencing the appearance of conducts and structures that ease the capture of solar radiation.
Many of the plants that live beneath the canopy do not receive enough light, so they are adapted to living in the shadows. For example, the Elephant Ears (Alocasia korthalsii) has huge leaves that make capturing the faint sunrays that penetrate the canopy easier. It even has a purple layer under each leaf to reflect light. This way, there are also other plants that grow among the trees and act as parasites, absorbing its nutrients and water.
Another interesting behavior is the one conducted by organisms that don’t take advantage of their host, but do use them in order to climb towards the light.
They depend of taller trees for their support because most of them are incapable of standing vertically after reaching a certain height. Climbing plants are in this situation, like lianas, which have stems similar to cords or cables, they twist them around their supports, reaching and stretching along the tops of the trees.
Fauna in tropical forests
It is possible to analyze the fauna that dominates tropical forests according to their location regarding plants stratums.The group that lives and feeds in the emergent layer is mainly made up of insects, bats and carnivorous birds. Among the latter, the Harpy Eagle (Harpia Harpyia) is a standout; a huge bird with a wingspan of two meters that uses its strong, large claws to mainly catch monkeys and sloth, lunging at them at a speed of nearly 70 kilometers and hour.
In the canopy of the tropical forest we can find a great variety of birds, fruit eating bats (they consume fruit) and insectivore mammals or consumers of leaves, fruit and nectar. Toucans move around din this area, as do many of the primates that dominate the jungle, like orangutans and spider monkeys. Squirrels also inhabit this sector, but they go up and down the tree trunks looking for food.
The herbaceous level is mainly dominated by reptiles and amphibians, like boas, anacondas and frogs. These last ones find an excellent environment to deposit their eggs in the puddles formed in trees. On the forest floor we find larger herbivores and carnivores. In the first group we find gaurs and tapirs, among others, while their predators are mainly tigers, leopards and jaguars.
The final stratum of consumers includes small animals that live on the surface of the ground or under it, such as birds and small mammals with certain climbing skills, which look for their food around the fallen leaves on the ground and in parts of the trunks.
This stratum is made up of insectivores, carnivores and mixed consumers.
Animal behavior
Since a large part of the animals live in the treetops (only the larger ones do so on the ground), they have developed interesting mechanisms in order to get around.
Birds have short wide wings to advance and spin between the branches, like the Bird of Paradise (Paradisaea raggiana), while other species have skin extensions that act as wings, allowing them to glide between the treetops. The Flying Squirrel (Glaucomys volans) is one of them, as it counts with a hair covered membrane that goes from its wrists to its ankles, and it pulls it out every time it passes from one tree to another.
The ones that have developed an extraordinary ease for moving around the trees are primates, who use their hands, feet and tail to cover considerable distances. This process of arboreal locomotion, which not only requires reaching the precise branches to move, but also the strength to hang, called brachiation. The Orangutan (Pongo pygmaeus) performs this important action , managing to quickly swing from the trees with its long arms and strong fingers. Another incredible adaptation is the use of the tail as a fifth limb, which is dubbed prehensile tail.
Many of the animals that inhabit tropical forests have also developed camouflage. The Jaguar’s (Panthera onca) skin allows it to pass undetected by others species stalking it. The same happens with some reptiles (like the Chameleon) and bugs, which blend in with the foliage or trees branches, managing to go unnoticed to their predators. But there is not only color and texture camouflage, there is also camouflage that mimics natural shapes, like lianas, leaves or branches.
Inhabitants of the jungle
Characters of fantastic stories, myths and legends, the first inhabitants of tropical forests coexisted in harmony with their surroundings for many years. In the beginning, hunter-gatherer people wandered these dense forests, making use of a variety of species. They not only fed on animals they hunted, but also on fruit, roots and leaves. Their populations were small and the impact of their activities on the environment around them was minimal.
Later on, the people that became sedentary established small permanent settlements and cultivated, in limited areas, products that they added to the previous diet. For their crops, they devastated the area’s typical vegetation. Although this was a foreboding of one of the problems that would affect tropical forests years later, its impact was small, as the forest was capable of regenerating some areas and sustaining this type of agriculture on a small scale.
Green destruction
Despite the fact that a great portion of the forest resources man has exploited come from temperate forests, tropical forests have constituted an attractive source of natural wealth during the last few decades. According to research, around 20 million hectares are cut down or damaged annually, placing plant diversity in serious peril. This phenomenon even has direct effects on the regions’ climate and on the transference of oxygen and carbon dioxide towards and from the atmosphere.
Another impact that comes from tree felling or other human activities is the destruction of habitats. When Man takes over this land for agricultural labor, he devastates all vegetation and burns it, leaving a flat surface, which after awhile will not even serve for the preordained purposes. This not only generates a vast area of land that will be left useless in the future, but also affects nearby areas because the intervened area hardens, capturing less water, which runs off and floods other places.
The destruction even has an influence of the disappearance of many plant species and on the moving and death of many animals, which no longer count with the same resources to survive.
Another problem that mainly affects the more exotic animals that inhabit tropical forests is the trafficking of species to exploit them commercially, as occurs with the skins of many mammals, or with many organisms that are sold as pets, like some turtles, snakes and many colorful birds for example.
Muere Evita