ABIOTIC FACTORS OF THE FOREST AND THEIR CHARACTERISTICS - BIOLOGY - 2024

The abiotic factors of the jungle are all those non-living components of the environment that affect organisms and regulate the functioning of the forest.

These components include both physical conditions and non-living resources that affect and in many cases condition living organisms in terms of growth, maintenance and reproduction. Abiotic factors include light, temperature, humidity, and soil.

Aerial view of the Amazon rainforest. Taken and edited from: Yulimar Rojas, from Wikimedia Commons.

On the other hand, the dense forests are called jungle, with lush and broad-leaved vegetation and with their very closed canopy. This ecosystem is home to great biological diversity.

The vegetation usually has several floors or levels, with a biodiverse understory. The forests are located in the intertropical zones and are typical of hot climates and low altitudes. About 66% of the terrestrial species live in the forests, however, medium and large species are not frequent.

Abiotic factors in the jungle

Sunlight

Sunlight is the main source of energy for all terrestrial ecosystems. In the jungle, due to its mainly intertropical location, there is a good availability of light throughout the year.

However, most of this energy is absorbed before reaching the ground. The canopy of trees measuring up to 30 meters takes advantage of most of this energy, estimating that only 1% of the light reaches the ground.

In adaptation to these conditions, larger plants have small leaves to reduce water loss due to direct exposure to sunlight.

The understory plants have large leaves to take advantage of the light that manages to pass through the upper canopy. The vegetation of the lower stratum is dominated by mosses.

Many small species have adapted to epiphytic life, growing on larger plants to gain access to sunlight.

Floors

The soils of the jungle are fine, very shallow, of low pH and with low content of nutrients and soluble minerals, if considered from the point of view of the requirements for agriculture.

This is because organic matter is decomposed by heat and moisture very quickly. The nutrients are subsequently washed away by the intense rains, cleaning the soils.

As a result of the constant cleaning of the soils by the rains, the nutrients in the forest are mainly found in the roots and leaves of the trees, as well as in the litter and other decomposing remains of vegetation on the ground and not in the ground in itself.

Another characteristic of these substrates is their low pH. As an adaptation to this type of soil, large trees developed shallow roots, as well as structures that serve as buttresses to support their trunk and branches.

Humidity

Humidity in forests is very high. Average annual rainfall can be between 1500 and 4500 mm. These precipitations must be very well distributed during the year.

Because of this, the average humidity levels are between 77 and 88%. Trees also provide water through perspiration. The air under the upper canopy of the rainforest is stable and very humid. The soil also remains moist due to the little amount of sunlight that reaches it.

Temperature

The temperature in the jungle has an annual average of 25 ºC. This can oscillate between 27º and 29º C in the tropical forest, while in the subtropical forest it presents an average of 22 ° C, and in the mountain forest 18 ° C.

Constant high temperatures allow humidity levels to be kept high by perspiration from plants. They also allow rapid growth of both plants and animals.

The latter must not expend energy to keep warm, which allows them to use more energy to reproduce more frequently. This explains the productivity and biodiversity that can be found in the jungle.

Types of forests

These ecosystems can vary depending on various variables, among which we can mention the amount of available water and the temperature and its temporal variability, as well as its geographical and altitudinal location.

These can be classified in various ways, among which we can mention:

-According to temperature and geographical location

Equatorial rainforest

Located in the equatorial zone. It is the most exuberant and biodiverse. Its temperature throughout the year is close to 27ºC and its precipitation ranges from 2000 to 5000 mm per year. It is located in the Amazon region, Congo (Africa) and between the Indomalayan region and Australasia (Malaysia).

Rain forest

Also called tropical forest or macro-thermal forest. The average annual temperature is above 24ºC. Rainfall has an annual average slightly lower than that of the equatorial forest.

It is located in the area where the north and south trade winds converge. In North America it reaches as far as Mexico, while in Africa it reaches as far as Mozambique, and even Madagascar. Some authors consider it synonymous with the equatorial jungle.

Subtropical jungle

It has an average annual temperature between 18 and 24ºC. Average annual rainfall ranges between 1000 and 2000 mm, although they can reach 4000 mm.

It is the type of jungle found in areas of the subtropical climate with high humidity content, with very hot summers and winters with relatively low temperatures.

In South America they are located in the south of Brazil, in Paraguay and the northernmost part of Argentina. In South Africa, as well as in Australia, they are located in coastal areas.

-According to the amount of water and seasonality

Rain forest

This type of jungle is, according to some authors, the true jungle. Humidity can be high or very high. Due to the seasonality of the rains, the vegetation can be always green and up to 50% of the trees can lose their leaves in the dry season.

Rainforest of Costa Rica. Photograph by: Kevin Casper. Taken and edited from: publicdomainpictures.net

Dry jungle

Also known as tropophilic forest, it is characterized by an alternation between short rainy seasons and seasons without rain. They are tropical rainforests in dry areas.

Its specific diversity per hectare is lower compared to the rainforest. It has a greater number of specimens per species, which is why it is generally subject to excessive commercial exploitation.

-According to the altitude

Basal jungle

It is located below 500 - 1000 m asl depending on the criteria of different authors. It is also known as plain or plain jungle. The land may or may not be flooded or permanently flooded.

Mountain jungle

It limits elevationally with the mountain forest in the upper part and with the low forest in the lower part. It differs from the mountain forest because the latter has a lower density and higher altitude. It is also known as montane, cloudy or high jungle.

Gallery jungle

The forested ecosystem that surrounds the rivers of the savanna plains is named in this way, it is typical of the intertropical zone.

References

1. PS Bourgeron (1983). Spatial aspects of vegetation structure '. In FB Golley (Ed.). Tropical rain forest ecosystems. Structure and function. Ecosystems of the world. Elsevier Scientific.
2. FS Chapin, PA Matson, HA Mooney (2002). Principles of terrestrial ecosystems ecology. Springer, New York.
3. EP Odum (1953). Fundamentals of ecology. Philadelphia: Saunders.
4. Rainforest. On Wikipedia. Recovered from en.wikipedia.org.
5. Jungle. On Wikipedia. Recovered from es.wikipedia.org
6. RH Waring, WH Schlesinger (1985). Forest ecosystems: Concepts and management. Academic Press, New York.