THERMAL FLOORS: HISTORY, CLASSIFICATION, FLORA AND FAUNA - ENVIRONMENT - 2024

The thermal floors or climatic floors are temperature ranges that are related to an altitude gradient. These are particularly applicable in mountainous geographic areas.

There are important differences between the thermal floors of temperate and tropical zones. In temperate zones they are not clearly defined, because the annual seasonal temperature variations overlap the altitude.

Thermal floors of the intertropical zone. Modified from Chris.urs-o; Maksim; Anita Graser, via Wikimedia Commons

In the intertropical zone the annual temperature variation is very small. Therefore, it is possible to determine the climatic characteristics of the thermal floors associated with the altitudinal ranges.

There are several factors that can affect the climate of the thermal floors. Among these we have the altitude, the relief, the effects of the wind and the proximity of land areas to the sea.

The biodiversity present in each thermal floor is variable in the different regions of the planet. However, as a general rule the number of species increases from the warm to the temperate and very cold thermal floor, while in the upper floors the biodiversity is lower, even when there are a large number of adaptations to extreme climatic conditions.

History of the study of thermal floors

In the eighteenth century, some researchers evidenced climatic zones in different altitudinal gradients in high European mountains. Later, in the nineteenth century Humboldt and Bonpland in their travels through America observed the same phenomenon.

During 1802, Humboldt and Bonpland, along with the Colombian Francisco Caldas, studied the climate of the Andean mountains. These naturalists found that the altitude gradients determined a marked thermal gradient. From this information, they made the proposal of the thermal floors for the tropical Andes.

Subsequently, Humboldt, based on his observations from all his travels in America, made some adjustments to the original proposal.

Subsequently, other modifications have occurred by different authors, basically referring to the altitudinal gradients in the American tropics and the use of the terminology used. Also, proposals have been made for different altitudinal ranges to define thermal floors.

Classification

The definition of thermal floors has been made mainly for mountainous areas, because in this type of relief the altitude conditions many climatic characteristics. Thus, climate classification systems based on thermal floors only take into account the variation of temperature with altitude.

However, some climatologists do not consider thermal floors as a climatic classification, since they do not take into account other factors such as precipitation.

They have tried to establish floors or thermal belts that can be applied throughout the world. However, this is difficult due to the climatic differences between temperate and tropical zones, so a different classification has been established for both zones.

One of these approaches was developed by Körner and collaborators in 2011. The authors propose the existence of seven thermal floors without taking into account the altitude, in order to be able to compare the mountains of different places on the planet.

This classification takes into account the temperature and the presence of the tree line in the mountains. Thus, above the tree line are the alpine and snow floors with average temperatures <6.4 ° C.

-Temperate areas

In these areas it is difficult to clearly establish the ranges of the thermal floors, since various factors affect the altitude temperature gradient. Among others we have the exposure to radiation and winds, as well as the latitudinal position.

In temperate zones, more than thermal floors, bioclimatic floors have been proposed. The definition of these floors combines the temperature with the vegetation present in a given altitude range.

Bioclimatic floors are defined based on the average annual temperature and that of the coldest month of the year. The Eurosiberian region is differentiated from the Mediterranean region mainly by the type of vegetation. The altitude at which these bioclimatic floors occur varies in each region.

In the Eurosiberian region there are 5 different floors. The lower end is the thermocholine with a mean annual temperature of 14-16 ° C. While the alpine floor has annual average temperatures between 1-3 ° C.

For the Mediterranean region, the temperature gradients are similar. The infra-Mediterranean floor presents average temperatures of 18-20 ° C and the cryo-Mediterranean between 2-4 ° C.

-Intertropical zone

It is characterized by the occurrence of an average annual temperature above 20ºC. In addition, the annual thermal variation is less than 10 ° C, so there are no well-defined thermal stations. However, the daily thermal oscillation can be quite marked.

In this area it is possible to define altitudinal ranges associated with the temperature gradient, which has allowed the thermal floors to be defined more clearly.

The terminology used to name the thermal floors varies in different countries. The altitude and temperature ranges tend to present few differences. However, the average temperature of the upper floors is defined by the altitude of the mountain systems in each region.

In this case we present a combination of the thermal floors proposed by Francisco Caldas for Colombia, and Silva for Venezuela.

Warm

The warm thermal floor is located between 0-1000 m in height. The upper limit can go up to 400 m depending on the locality. Average temperature values ​​are above 24 ° C.

Within this thermal floor, Silva recognizes two categories. The hot floor ranges from 0-850 m altitude with average temperatures between 28-23 ° C.

The cool floor is located above 850 m and the temperature range is between 23-18 ° C.

Tempered

The temperate thermal floor occurs within an altitude range of 1000 - 2000 m. The amplitude margin is ± 500 m. The annual temperature range is between 15.5 - 13 ° C.

Cold

The cold thermal floor is located between 2000-3000 m, with a limit of ± 400 m. Average annual temperatures range from 13 - 8 ° C.

Very cold

The very cold thermal floor is also called low moor. This altitudinal floor is located above 3000 m to 4200 m. The average annual temperature ranges from 8-3 ° C.

Icy

This thermal floor is known as high páramo in the Caldas classification. It is located above 4200 m. Average annual temperatures can reach values ​​below 0 ° C.

How does the climate change on thermal floors?

Some factors can affect the climate present in the different thermal floors. Local conditions, such as exposure to the wind or proximity to the sea, can define particular climatological characteristics.

Altitude and temperature

As altitude increases, less air mass is produced. This causes the atmospheric pressure to increase and the temperature to decrease.

On the other hand, at higher altitudes the solar radiation affects more directly, since it must pass through a smaller air mass. This causes high temperatures to be reached at noon.

Later, when radiation decreases throughout the day, the heat dissipates more quickly. This occurs because there are no air masses that contain it, causing the daily thermal oscillation to be very marked.

For the intertropical zone, where the annual thermal variation is low, the altitude is a determining factor. It has been established that in the tropics, for every 100 m of altitude, the temperature decreases by approximately 1.8 ° C.

In the temperate zone, these variations occur, but they are influenced by the annual thermal variation of each region.

Relief

The exposure of the slopes of a mountain can affect the climatic conditions. This is determined by the orientation and slope of the slope.

The so-called windward slope is more exposed to humid winds from the sea. When these masses of humid air collide with the mountain, they begin to rise and the water condenses.

On this slope there will be more precipitation and the area will be more humid. In this type of slope, the cloudy mountain forests are usually established, very rich in biodiversity.

On the leeward side, the rainfall is less since it is not directly exposed to the sea winds.

Continentality

The distance from land areas to large bodies of water will directly influence the climate. As a region is further away from the water, there is less chance that moist air will reach them.

The oceans cool more slowly than the continents. The air coming from the water masses is warmer, so it can control the thermal oscillations in the terrestrial areas.

The further a region is from the water masses, its daily or annual thermal oscillations will be greater. Similarly, areas further from the oceans tend to be drier.

Effect of the winds

The movement of local and regional winds can determine the climatic conditions of a region.

Thus, there are differences in the direction of wind movement between day and night between valleys and mountains. This is caused by differences in air temperature at different elevational gradients.

Valley winds move toward the mountains from early morning to noon, because the air in the valley has not yet warmed up.

Later, during the day the temperature of these air masses increases and the wind direction changes from the mountains to the valleys.

The orientation of the mountainside also determines the effect of the movement of the winds. Towards the windward side, rising air can lead to more precipitation. In addition, it can lead to an increase in temperature on the various heated floors.

On the leeward side, the air descending from the mountain can considerably increase the temperature of the lower thermal floors.

Flora and fauna

Depending on the thermal floor, biodiversity can be more or less abundant. In both temperate and tropical regions, some characteristics of the thermal floors can lead to similar adaptive mechanisms.

For example, in the higher thermal floors, the climatic conditions tend to be more extreme. Generally the precipitation is low, the daily thermal oscillations are great and there is a high radiation.

Plants that grow in these environments tend to have compact shapes that help them resist the winds. On the other hand, they have characteristics that allow them to resist high radiation and temperature during the day. Likewise, some have mechanisms to regulate the temperature in the face of severe daily temperature fluctuations.

As for animals, in the case of mammals they have very thick coats, which helps to regulate their temperature. Likewise, in temperate zones the change of coat and plumage color is common between winter and summer.

When we approach lower thermal floors, the climatic conditions are less severe. This allows a greater diversity of plants and animals to develop.

The flora and fauna of each thermal floor will depend on the region of the planet in which it occurs. Here we will present some examples of the biodiversity in the thermal floors of the American tropics.

Warm thermal floor

Regarding the flora, on this floor the type of vegetation is determined by the availability of water. They develop from formations of cacti to large wooded areas.

We can highlight various species of legumes. Likewise, cultivated plants such as cacao (Theobroma cacao) and cassava (Manihot esculenta) are also frequent.

The fauna is very diverse depending on the geographical area. Birds are abundant, with numerous species of parrots (parrots and macaws). Also, mammals, amphibians and reptiles are abundant.

Tempered thermal floor

It is basically occupied by forest ecosystems. Large trees of Anonnaceae and Lauraceae are frequent. The cultivation of coffee and some varieties of avocados is common.

There is a great variety of birds. Small arboreal mammals, primates and felines occur in the jungles. Likewise, there is a great diversity of amphibians, small reptiles and numerous insects.

Cold thermal floor

Most of the so-called cloud forests are located in this area. These ecosystems present a high diversity due to the high humidity conditions.

Epiphytes are frequent. There is a great abundance of orchids and bromeliads. Climbing plants are also frequent, since one of the limitations for plant growth is light.

There is an abundance of palms and large trees with highly developed tabular roots, due to the shallow soils.

The fauna is equally diverse. Amphibians such as frogs and salamanders are abundant due to the high humidity conditions. There are also a large number of bird species. Small mammals predominate, from the group of rodents, but large mammals like the tapir and jaguar also inhabit the Andes.

Very thermal floor

This floor is known as the páramo ecosystem. The climatic conditions are extreme for the development of the vegetation.

There is a predominance of Asteraceae species. A distinctive group of this thermal floor are the frailejones (Espeletia spp.). Also various species of stunted shrubby plants.

As for the fauna, some emblematic species stand out. Among the birds we have the condor of the Andes (Vultur grhypus). Within mammals, the spectacled or frontin bear (Tremactos ornatus). Both species are in danger of extinction throughout their range.

From Peru to Argentina is the guanaco (Lama guanicoe), from which the Incas selected the Llama (Lama glama).

Icy thermal floor

In the icy thermal floor there is always the presence of snow, so biodiversity is scarce or non-existent.

References

1. Chasco C (1982) New names for the vegetation levels of the Mediterranean region. Annals of Geography of the Complutense University 2: 35-42.
2. Eslava J (1993) Climatology and climatic diversity of Colombia. Rev Acad.Colomb. Science. 18: 507-538.
3. Körner C (2007) The use of altitude in ecological research. Trends in Ecology and Evolution 22: 569-574.
4. Körner C, J Paulsen and E Spehn (2011) A definition of mountains and their bioclimatic belts for global comparisons of biodiversity data Alp. Botany 121: 73-78.
5. Messerli B and M Winiger (1992) Climate, environmental change and resources of the African Mountains from Mediterranean to the Equator. Mountain Research and Development 12: 315-336.
6. Silva G (2002) Classifications of thermal floors in Venezuela. Venezuelan Geographical Magazine 43: 311-328.