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Edita: Sociedad SURCOS, Avda. Torreón, nº 1 13001 Ciudad Real –

Depósito Legal: CR 820-1986- - ISBN 84-398-6347-0 ISSN 2445-1304 -  Aviso Legal

 

Contacto: Soledad López Fernández, solpfernandez@gmail.com

 

 

Volumen V

Año: 2018

Artículo

nº 8

Aceptado

26 de junio 2018

 

 

Worldwide Bioclimatology Manual and Guide

 

Manual y Guía de Bioclimatología Mundial

 

Authors:

LOPEZ FERNANDEZ, MARIA LUISAmllopez@unav.es (Departamento de Biología Ambiental, Facultad de Ciencias, Universidad de Navarra), 31008 Pamplona.

LOPEZ, SOLEDADsolpfernandez@gmail.com (Instituto de Estudios Manchegos), 13002 Ciudad Real, España.

 

(English version, made by M.L. Lopez Fernandez, of  "Manual y Guía de Bioclimatología Mundial, 2017", http://www.naturalezenhispania.com, by the same authors).

 

 

ABSTRACT:

López, Fernández, M.L.& López Fernández, M.S. (2018). “Worldwide Bioclimatology Manual and Guide”. Documentos Aljibe “on-line”, vol. V, n.8., 26 de junio de 2018. Ciudad Real. Edita Sociedad Surcos. Depósito Legal: CR 820-1986- - ISBN 84-398-6347-0 ISSN 2445-1304. http://www.naturalezenhispania.com.

 

A summary exposition of Rivas-Martínez & al. (2011) “Worldwide Bioclimatic Classification System, Global Bioclimatics", is given. We comment, usually in their own words, on the originality of its premises, its basic elements, its hierarchical levels, its Isobioclimates, the Ombroclimographes (or Ombrolimogrames), and the Synoptic Table of the Bioclimatic Classification of the Earth. With the help of the information contained in the web: “http://www.globalbioclimatics.org”, Rivas-Mart. & Rivas-Sáenz (1996-2017), an approach to World Bioclimatic Diversity is given. Also, as a complement to the theoretical exposition, a practical example of how to perform the Bioclimatic Classification of a weather station is provided. Finally, the possibility of performing bioclimatic thematic maps, is commented, with bibliographical mention of the most recent maps. As for us, we have expanded the Bioclimatic Variants of Rivas-Mart. et al. (2011), with the concept of Normal Variant. We have also added some precisions to their concept of Steppic Variant. We give a glossary of concepts, which, in the offered pdf file, indicates the pages in which each of the terms is used.

 

Key words: Macrobioclimates, Bioclimates, Bioclimatic Variants, Bioclimatic Belts, Thermotypes, Ombrotypes, Isobioclimates, Ombroclimograms, Continentality, Steppicity, Submediterraneity, Global Bioclimatic Diversity, Bioclimatic Maps.

 

RESUMEN

López, Fernández, M.L.& López Fernández, M.S. (2018). “Worldwide Bioclimatology Manual and Guide”. Documentos Aljibe “on-line”, vol. V, n.8., 26 de junio de 2018. Ciudad Real. Edita Sociedad Surcos. Depósito Legal: CR 820-1986- - ISBN 84-398-6347-0 ISSN 2445-1304. http://www.naturalezenhispania.com.

 

Se realiza una exposición resumida de la Clasificación Bioclimática Mundial, "Global Bioclimatics", de Rivas-Martínez & al. (2011), comentando, muchas veces con sus mismas palabras, la originalidad de sus premisas, sus elementos básicos, sus niveles jerárquicos, los Isobioclimas, los Ombroclimografos (u Ombroclimogramas), y la Tabla Sinóptica de la Clasificación Bioclimática de la Tierra. Con ayuda de la información contenida en “http://www.globalbioclimatics.org”, Rivas-Mart. & Rivas-Sáenz (1996-2017), se hace una aproximación a la Diversidad Bioclimática Mundial. Así mismo se ofrece un ejemplo práctico de cómo realizar la clasificación bioclimática de una estación meteorológica, que complementa la exposición teórica. Para terminar, se comenta la posibilidad de realizar mapas temáticos bioclimáticos, con mención bibliográfica de los más recientes. Por nuestra parte, hemos ampliado las Variantes Bioclimáticas de Rivas-Mart. et al. (2011), con el concepto de Variante Normal, así como también hemos añadido algunas precisiones a su concepto de Variante Esteparia. El trabajo se acompaña de un glosario de conceptos, que, en la versión PDF que se ofrece, indica la página en que se utiliza cada uno de ellos.

 

Palabras clave: Macrobioclimas, Bioclimas, Variantes Bioclimáticas, Pisos Bioclimáticos, Termotipos, Ombrotipos, Isobioclimas, Ombroclimograma, Continentalidad, Estepicidad, Submediterraneidad, Diversidad Bioclimática Mundial, Mapas Bioclimáticos.

 

 

General Index

  1.- Introduction

  2.- Premises of the classification

  3.- Basic Elements for the Global Bioclimatic Classification

  4.- Worldwide Bioclimatic Classification

  5.- Bioclimatic Synopsis of the Earth

  6.- Isobioclimates

  7.- Bioclimograms

  8.- Approach to Global Bioclimatic Diversity

  9.- Assessment of Summer Aridity, with examples

10.- ITC and Ci Calculations

11.- Practical example of complete bioclimatic characterization of a meteorological station, and of the use of the synoptic table

12.- Bioclimatic Cartography

13.- Paginated glossary

14.- Table of contents

15.- Bibliography

 

1.- INTRODUCTION

Bioclimatology is the science that studies the relationship between climate and the distribution of living beings and their communities on Earth.

Since approximately 1987, Rivas-Martínez has developed a new "Bioclimatic Classification of the Earth", the "GLOBAL BIOCLIMATICS" of Rivas-Martínez (1987, 2004, 2008). Precisely, also in 2008, López Fernández & López Fernández published a "Guide to Recognizing and Classifying Bioclimatic Units", with the aim of facilitating the understanding and use of Rivas-Martínez's "Global Bioclimatics".

Recently, Rivas-Martínez & al., 2011, have remodeled and completed the "Global Bioclimatics", also called "Worldwide Bioclimatic Classification System", which exclusively uses climatic data. The Worldwide Bioclimatic Classification, by Rivas Martínez & al., is hierarchical and recognizes three levels: Macrobioclimate, Bioclimate / Variant, and Bioclimatic Belt - consisting of a Thermotype and a Ombrotype.This new Bioclimatic Classification recognizes in the Earth 5 Macrobioclimates, to which are subordinated 28 Bioclimates - in each one of which operate one or more of the nine recognized Bioclimatic Variants, and, in addition, 31 Thermotypes and 9 Ombrotypes: Altogether, over 400 elemental bioclimatic combinations, known as Isobioclimates, each of one consisting of a Macrobioclimate, a Bioclimate / Variant and a Bioclimatic Belt (a Thermotype plus an Ombrotype), which have territorial representation in the Geobiosphere.

With this "Manual and Guide to World Bioclimatology", we aim to facilitate the understanding and use of this bioclimatic classification tool, so useful to explain and understand Biogeography.

 

2.- PREMISES OF THE BIOCLIMATIC CLASSIFICATION OF THE EARTH, RIVAS-MARTÍNEZ & al. (2011)

The following eight premises bring together the main lines of force that condition the distribution of life, as interpreted by Rivas-Martínez (2008) and Rivas-Martínez & al. (2011), so they are at the basis of their Earth's Bioclimatic Classification.

2.1. Reciprocity: In Bioclimatology, it has been shown that there is an adjusted and reciprocal relationship between climate, vegetation and geographical territories, ie, between Isobioclimates, biocenosis and biogeographical units. This is because the distribution of vegetation, as well as the evolution of the biocenosis, have accompanied and accompany the climatic oscillations and the geological variations of the earth, which have taken place in the past. (Exceptionally, some high alpine ridges have prevented vegetation migrations and that reciprocity: see premise 8: Orogenies, below)

2.2. Photoperiod / Latitude: In the distribution of life have great influence, both the photoperiod and its variation throughout the year, as well as the angle with which the sun's rays affect the surface of the Earth, both phenomena controlled by latitude. Therefore, latitude is the first factor used to characterize and differentiate Macrobioclimates.

2.3. Continentality / Oceanicity - Annual thermal amplitude: The annual thermal amplitude has an influence of first magnitude in the distribution of the biocenosis and, consequently, in the borders of many Bioclimates. In the Synoptic Table of the Earth's Bioclimatic Classification (see Figure 7, below), it can be seen how the Continentality is used to differentiate the Temperate Macrobioclimate from the Boreal Macrobioclimate, as well as all the Bioclimates from each other except the Tropical.

2.4. Seasonality of Precipitation: The annual rhythm of precipitation has as much or more importance, in the composition and distribution of the biocenosis, than the amount of rain itself. The annual rhythm is the distribution of precipitation throughout the year. Seasonality differentiates bioclimatic units of several ranges: Macrobioclimates, Bioclimates and Bioclimatic Variants.

2.5. Mediterraneity: There is a large Mediterranean Macrobioclimate, latitudinally extratropical, ombrically antithetical to the Tropical, Temperate and Boreal Macrobioclimates, showing a summer aridity (or summer drought) of at least two consecutive months: That is to say, in which the sum of the precipitations of the two consecutive driest months of the summer quarter is less than or equal to twice the sum of the average monthly temperatures of those same months: (Psi + Psii)  2 ( Tsi + Tsii), being si and sii the two consecutive months drier of the summer. Such a shortage of rain during the summer, which can last up to the twelve months of the year, is a brake for life, just during the months thermally more favorable to growth. This circumstance is reflected in deep physiognomic changes of the biocenosis, with respect to other Bioclimates with precipitations of similar quantity, but without summer drought.

2.6. Deserts: The deserts are the response of life to extremely unfavorable climatic conditions, either by cold, or by aridity, or by both. That is why there is no single type of desert bioclimate for all the deserts of the world, but there are cold deserts, in all Macrobioclimates, and warm deserts, in the Tropical and Mediterranean Macrobioclimates. In warm deserts, the rate of precipitation is decisive, with maximums in summer - tropical deserts - or in autumn and spring – Mediterranean deserts. The flora and vegetation of both types of deserts are clearly different and are phenologically adapted to the precipitation rhythms.

2.7. Oroclimates (Mountain climates): In the mountains, the Bioclimate, except for temperature and precipitation values, shows a close relationship, in the photoperiod values, with that of its piedmont. Therefore, in the mountains, just as there is a certain vertical zonation of the biocenosis, there is also, for each Macrobioclimate, a particular sequence of thermotypic and ombrotypic combinations, that is to say, a particular sequence of Bioclimatic Belts. So that the altitudinal succession of vegetation floors is explained by thermal and ombric changes due to altitudinal and / or exposure-orientation changes.

2.8. Orogenies: In some regions of the Earth, paleogeological, orographic and paleoclimatic circumstances have prevented the free migration of the biocenosis, in correspondence with the climatic variations that were occurring. Therefore, in those regions, the reciprocal relationship between climate and distribution of the biocenosis, announced in the first Premise, can not be met. One such circumstance has been the Alpine orogeny, which gave rise to an almost continuous set of high mountain systems oriented East-West (Hindu Kush, Himalayan, Tibet and Karakorum, etc.) on the Asian continent. These reliefs, of considerable altitude, have acted as a barrier, greatly limiting the migratory movements of life forms, during the great climatic changes that followed. Thus, in addition to the severe extinctions during arid or glacial periods, these large Central Asian transverse ridges have prevented the biocenotic recolonizations from the adjacent subtropical belt during the interglacial and, ultimately, during the Holocene periods. As a consequence, between the meridians 70º and 110º E, and between the 25º and 35º N parallels, it was necessary to establish the altitudinal limit of 2,000 meters, as an approximate border between the Tropical Macrobioclimate on the one hand, and the Mediterranean and Temperate Macrobioclimates, on the other.

 

3.- BASIC COMPONENTS FOR THE WORLDWIDE BIOCLIMATIC CLASSIFICATION

After having seen the Premises that underpin this Worldwide Bioclimatology, we will now comment on its basic elements, namely: Latitude, Annual distribution of rainfall, Bioclimatic Parameters, and Bioclimatic Indices.

All the necessary data for the Bioclimatic Classification of the Earth are offered even by the simplest thermopluviometric stations. These are the following data: Name and Country; Latitude, Longitude and Altitude; period of temperature and precipitation observations; monthly averages of maximum and minimum temperatures; and monthly rainfall. In total, 43 data are needed from each meteorological station.

However, let us note that the great work of Rivas-Martínez and his team has been the double selection they have achieved: First, they have selected the parameters and indices that are significant for the distribution of life and which are easily obtained from the 43 basic data provided by the meteorological stations; And secondly, they have once again made a successful selection by assigning, at each step of the bioclimatic hierarchical classification, those parameters and indices that make it possible to differentiate these levels. All these selections are not subjective, but have been made by relating the different types of ecosystems to the climatological data offered by the stations (more than 20,000, worldwide, collected by Rivas Martínez, in the database of his Phytosociological Research Center, Spain, http://globalbioclimatics.org/).

In doing so, the predictive value of the result, that is, of the World Bioclimatic Classification, is truly astounding. But in reality, what should astound us is the knowledge of the different forms of life and their distribution-geographic positioning at world-wide level, and the work of relating that knowledge with the climatic data.

 

Next, we will discuss the following five topics:

3.1.- Latitude: Latitudinal Zones and Bands.

3.2.- Seasonality of temperatures and rainfall. Period of plant activity. Types of frost.

3.3.- Parameters

3.3.1.- Seasonal Parameters

3.3.2.- Temperature Parameters

3.3.3.- Precipitation Parameters

3.4.- Bioclimatic Indexes

3.4.1.- Continentality / Oceanicity Index: Annual thermal amplitude - lc -

3.4.2.- Index of Thermicity It and Index of Compensated Thermicity Itc

3.4.3.- Ombrothermal Indexes - Io -

3.5.- Alphabetical list of the abbreviations that designate the Parameters and the Bioclimatic Indexes.

 

3.1.- Latitude: Latitudinal Zones and Waists.

The three factors that most influence the distribution of life - the photoperiod and its annual variation, the temperature and its seasonal variation, and the amount of precipitation along with its annual rhythm - have a close correlation with the values of latitude. It is therefore not surprising that the limits of the superior bioclimatic units in World Bioclimatology show a close correspondence with the latitudinal zones and bands traditionally proposed by geographers. In figure 1 we show the latitudinal Zones and Bands, for later, in figure 3, to point out and comment their correlations with the Macrobioclimates.

Latitudinal Zones. -In terms of latitude, at any altitude above sea level, large latitudinal zones are distinguished on Earth (see Rivas-Mart et al., 2011): one Warm – between the 35º North and South; two Temperate - between the 35º-66º N and S; and two Cold- between 66º-90º N and S.

 

Figure 1. Amplitude of latitudinal Zones and Belts recognized on Earth (according to Rivas-Mart et al., 2011):

 

Latitudinal Zones

Latitudinal

Belts

N

3. Cold

66º-90º

3a.

Arctic

66º-90º

2. Temperate

35º-66º

2b. Subtemperate

51º-66º

2a. Eutemperate

35º-51º

1. Warm

       0º-35º

1c. Subtropical

23º-35º

1b. Eutropical

7º-23º

1a. Equatorial

7ºN-7ºS

S

1. Warm

0º-35º

1b. Eutropical

7º-23º

1c. Subtropical

23º-35º

2. Temperate

35º-66

2a. Eutemperate

35º-51º

2b. Subtemperate

51º-66º

3. Cold

66º-90º

3a.

Antartic

66º-90º

 

Latitudinal Belts. - Depending on the latitude, at any altitude above sea level, 11 wide latitudinal belts are distinguished on Earth:

In the Warm Zone, the following 5 latitudinal Belts are recognized: one Equatorial Belt, 7º North - 7º South; two Eutropical Belts, 7º-23º North and 7º- 23º South; and two Subtropical Belts, 23º-35º North and 23º-35º South.

In the Temperate Zones, which contact north and south with the warm zone, 4 latitudinal belts are recognized: two Eutemperate Belts, 35º-51º North and 35º-51º South; and two Subtemperate Belts, 51º-66º North and 51º-66º South.

In the Cold Zones, which contact both in the North and the South with the Temperate zones, only two latitudinal belts are recognized, one Arctic belt, 66º-90º North and another Antarctic belt, 66º-90º South.

 

3.2.- Seasonality of temperatures and rainfall. Period of plant activity. Types of frost.

Seasonality refers to variations in temperature and precipitation occurring throughout the year. In tropical climates, seasonality is marked by precipitation, while, in the extratropical climates, seasonality is marked by temperatures.

The seasonality of temperatures and of precipitations is involved in the definition and formulation of most of the Parameters and Indexes used in this Worldwide Bioclimatic Classification, as we will see below. In fact, the seasonality of temperatures and the amount of monthly precipitation, as well as its annual rhythm, are data of great diagnostic value in the recognition and delimitation of Macrobioclimates, Bioclimates

One aspect of the seasonality of temperatures is the concept of "Plant activity period". "Plant activity period" is the number of months whose average monthly temperature exceeds a certain threshold to allow the biochemical activity of plants. The most accepted threshold is Ti> 3ºC. Another aspect of the seasonality of temperatures is the concept of "Types of frost", which may be: absent, probable or sure, depending on the magnitude of the parameters mi and m'i. It is said that a month has frost absent, when its m'i> 0; it is said that a month has probable frost, when it simultaneously fulfills mi> 0, and m'i ≤ 0; and finally, it is said that one month has sure frost, if mi ≤ 0.

 

3.3.- Parameters

We understand by Parameters the data or significant values of those climatic variables that are considered necessary to analyze a bioclimatic situation.

In order to establish this Worldwide Bioclimatic Classification, climatic data that are easily accessible have been used - average monthly temperatures of the maximum and minimum, and average monthly temperatures, expressed in degrees centigrade (ºC), and monthly precipitations expressed in millimeters (mm). All these data, which we consider as Parameters in this classification, are offered even by the simplest weather stations, which, altogether, form a wide network around the world.

The main Parameters of seasonality, temperature and precipitation used in this "Bioclimatic Classification of the Earth" are listed below by their acronyms and notations. (For more information, see Rivas-Mart et al., 2011):

3.3.- Parameters

3.3.1. – Seasonal Parameters

3.3.2.- Temperature Parameters

3.3.3.- Precipitation Parameters

3.3.1.- Seasonal Parameters

The sequence of atmospheric changes, and their duration, are of paramount importance to life. Therefore, in Bioclimatology, it is interesting to take into account the following periods of time - Seasonal parameters - during which vegetation and flora are especially sensitive to certain climatic values of temperature and precipitation.

We list the main Seasonal Parameters used in this Classification. From each one its acronym and its contents are indicated:

Tr1      Winter solstice trimester. Season: Winter (W, Winter). Dec-Jan-Feb, latitude N; Jun-Jul-Aug, latitude S.

Tr2      Spring equinox trimester. Season: Spring (P, Spring). Mar-Abr-May, latitude N; Sep-Oct-Nov, latitude S.

Tr3      Summer solstice trimester. Season: Summer (S, Summer). Jun-Jul-Aug, latitude N; Dec-Jan-Feb, latitude S.

Tr4      Autumn equinox trimester. Season: Autumn (F, Fall, Automn). Sep-Oct-Nov, latitude N; Mar-Abr-May, latitude S.

Cm1     The warmest four-month period of the year.

Cm2     Four-month period following the Cm1.

Cm3     Four-month period prior to the Cm1.

Pav      Period of plant physiological activity: number of months whose average monthly temperature equals or exceeds 3.5ºC: Ti ≥ 3,5ºC.

Pf         Periods of frost: number of months with frost absent, probable or safe.

Ss        Warmer semester of the year

Sw       Warmer semester of the year

3.3.2.-  Temperature Parameters

Are data, annual or monthly, of temperatura. We list them by their initials, indicating their content. Average temperatures are expressed in degrees centigrade and positive temperatures, in tenths of a degree centigrade.

T          Average annual temperature

Ti         Average monthly temperature, standing: 1 = January, ..., 12 = December

Tmax   Average monthly temperature of the warmest month of the year

Tmin    Average monthly temperature of the coldest month of the year.

Tp        Positive Annual Temperature: Quantifies, for each place, the thermal energy available for life. It is the sum, expressed in tenths of degree centigrade, of the average monthly temperatures of those months that exceed 0ºC: Tp=

Tps      Positive Temperature of the warmest trimester of the year (Tropical Macrobioclimate), or summer trimester (Macrobioclimates extratropical), expressed in tenths of degree centigrade.

Tpw     Positive Temperature of the coldest trimester of the year, expressed in tenths of degree centigrade.

Tsi       Monthly Medium Temperature of any Summer month

M         Average temperature of the maximum temperatures of the coldest month in the year, ie, the month with the lowest Ti.

m         Average temperature of the minimum temperatures of the coldest month in the year, that is, the month with the lowest Ti.

mi        Average monthly temperature of the mínimum temperatures, where i: 1 = January, ..., 12 = December.

m’i       Average monthly temperature of absolute minimum temperatures, where i: 1 = January, ..., 12 = December.

3.3.3.- Precipitation Parameters.

They are expressed in mm (or liters per square meter):

P          Annual precipitation.

Pi         Monthly precipitation, where i: 1 = January, ..., 12 = December.

Pss       Precipitation of the six warmest months of the year

Psw      Precipitation of the coldest six months of the year

Pcm1   Precipitation of the warmest four-month period of the year.

Pcm2   Precipitation of the four months period following the warmest four-month period of the year.

 Pcm3  Precipitation of the four months period previous to the warmest four months period of the year.

P Tr1   Precipitation of the winter solstice trimester. Season: Winter (W, Winter). Dec-Jan-Feb, latitude N; Jun-Jul-Ago, latitude S.

P Tr2   Precipitation of the spring equinox trimester. Season: Spring (P, Spring). Mar-Abr-May, latitude N; Sep-Oct-Nov, latitude S.

P Tr3   Precipitation of the summer solstice trimester. Season: Summer (S, Summer). Jun-Jul-Aug, latitude N; Dec-Jan-Feb, latitude S.

P Tr4   Precipitation of the automn equinox trimester. Season: Autumn (F, Fall, Automn). Sep-Oct-Nov, latitude N; Mar-Abr-May, latitude S.

Ps        Precipitation of the summer trimester -S, Summer. Jun-Jul-Aug, latitude N; Dec-Jan-Feb, latitude S.

Psi       Monthly precipitation of any Summer month

Pw       Winter trimester precipitation -W, Winter. Dec-Jan-Feb, latitude N; Jun-Jul-Ago, latitude S.

Psb1    Precipitation of the first two months after the summer solstice (July-August in latitude N, January-February in latitude S)

Psb2    Precipitation of the two subsequent months to Psb1 (September-October in latitude N, March-April in latitude S)

Pp        Annual Positive Precipitation: Pp = ∑Pi (Ti>0ºC). Pp is the sum of Pi of all months of the year, whose Ti is greater than 0ºC. Pp=∑Pi (Ti>0), being i: 1 = January, ..., 12 = December.

Pps      Positive Precipitation of the three warmest months period of the year (tropical zones), or of the summer trimester (extratropical zones).

Ppw     Positive Precipitation of the three coldest months period of the year (tropical zones), or of the winter trimester (extratropical zones).

> W>   Winter precipitation.

> P>     Spring precipitation.

> S>     Summer precipitation.

> F>     Fall precipitation.

 

3.4.- Bioclimatic Indexes

3.4.1.- Continentality / Oceanicity Index: Annual thermal amplitude -lc-

3.4.2.- Thermicity Index -It- and Compensated Thermicity Index -Itc-

3.4.3.- Ombrothermic Indexes -Io-

The indexes are the result of applying simple arithmetic formulas to various parameters of rainfall and / or temperature, selected by seasonal criteria or by criteria of specific biological requirements.

For this classification, Rivas-Martínez (2008) and Rivas-Martínez et al. (2011) have selected some Indexes, such as Continentality Index, already proposed by other authors, but, above all, they have created other new Indexes -the Thermicity Index as well as the Ombrothermic Indexes- which have great prediction capacity with respect to the distribution of the life.

It is precisely in the discovery of new Bioclimatic Indexes that the most brilliant part of the bioclimatic system of Rivas-Martínez (2008) and Rivas-Martínez et al. (2011), as we have already said. To discover and establish them, interpreting and following the dictation of the distribution of life and its dynamism, they have used all the ideas and demands contained in the Premises and the Basic Elements, already commented. They have also handled climate data from 20,000 stations around the world, which obviously reduces the subjectivism of choice.

3.4.1.- Continentality / Oceanicity Index: Annual thermal amplitude -lc-

The Continentality / Oceanity Index quantifies the amplitude of the annual thermal oscillation by calculating the thermal interval between the highest and lowest monthly average temperatures of the year. Although the index is called "Continentality Index", if its values are between 0 and 21, traditionally we talk about Oceanity, while, if they are high, over 21, we talk about Continentality. This Continentality Index, despite its simplicity, shows an excellent correlation with life. In addition, the data required for its calculation are provided by all weather stations, even the simplest ones.

The Continentality / Oceanity index expresses the difference, in degrees centigrade, between the highest and lowest monthly average temperatures of the year:

Ic = Tmax – Tmin

The Continentality Types and Subtypes recognized in the "Bioclimatic Classification of the Earth, together with their Ic intervals, are shown in Figure 1A.

Figura 1A. Types and Subtypes of Continentality, and their intervals of Ic.

TYPES

Ic VALUES

SUBTYPES

Ic VALUES

Hyperoceanic

  0≤Ic≤11

1.1 Ultrahyperoceanic

  0≤Ic≤4

1.2 Euhyperoceanic

  4<Ic≤8

1.3 Subhyperoceanic

  8<Ic≤11

Oceanic

11<Ic≤21

2.1 Semihyperoceanic

11<Ic≤14

2.1 Euoceanic

14<Ic≤17

2.3 Semicontinental

17<Ic≤21

Continental

21<Ic≤66

3.1 Subcontinental

21<Ic≤28

3.2 Eucontinental

28<Ic≤46

3.3 Hypercontinental

46<Ic≤66

 

3.4.2.- Index of Thermicity -It- and Index of Thermicity Compensated -Itc-

The Thermicity Index weighs and quantifies the intensity of the winter cold, a limiting factor for many types of life. It is calculated by summing T (mean annual temperature), M (mean temperature of the maximum of the coldest month), and m (mean temperature of the minimum of the coldest month), and expressed in tenths of a degree centigrade:

It = (T + M + m) 10

It is, therefore, an Index that considers together the intensity of the winter cold and the average annual temperature.

But since (M + m) is approximately, ≈2Tmin (Tmin = average temperature of the coldest month of the year), it is not necessary to know neither M nor m, to calculate It:

It ≈ (T + 2 Tmin) 10

The correlation of this Thermicity Index with vegetation is very satisfactory in countries with warm and temperate climates. However, in cold countries, or in countries with a continental tendency, the relationship with vegetation is more precise if the Annual Positive Temperature (Tp) is used. For this reason, it is a very useful Index to distinguish the Tropical Macrobioclimate from the Mediterranean and Temperate Macrobioclimetes, in those latitudes in which the three Macrobioclimates coincide (latitudes above 23 N and S). In the Mediterranean and Temperate Macrobioclimates, unlike in the Tropical, there is the winter: therefore, their lt is necessarily lower than in the Tropical.

Compensated Termicity Index.

As the Thermicity Index is greatly affected by the annual thermal amplitude - Continental Index, lc-, it needs a certain compensation, to make possible the comparisons between localities, regardless of the excesses of temperance or cold, that occur in hyperoceanic climates, or in the hypercontinental ones. It has been thus arrived at the Compensated Thermicity Index - Itc - which is no more than the value of It plus a compensation value, Ci:

Itc = It + Ci

Value of Ci.    Ci is the compensation value to correct for the excess "temperance" or "cold" occurring in extratropical areas (more than 23 ° N and S), when the Continental Index is extremely low (Ic ≤ 8), or high (Ic> 17), compared to cases where Ic has mean values:  In this way, the effect of an "excess" Ocean / Continental, on the measure of the climate thermal comfort, is neutralized. The value of Ci is calculated according to latitude and Continentality. Chapter 10 details the procedure for calculating Itc and Ci, with the help of several examples of stations with different Continental Indexes. (See Chapter 10).

As the truly meaningful Index is the Compensated Thermicity Index, Itc, we will always speak, in this work, of Itc. (In their study of the world's weather stations, see www.globalbioclimatics.org (Rivas-Mart. & Rivas-Sáenz, 1996-2017), authors indicate both It and Itc).

3.4.3.- Ombrothermic Indexes -Io-

They serve to measure the moisture comfort that life enjoys in the different terrestrial zones. The Ombrothermic Index relates the precipitation to the temperature, but using the Parameters of Positive Precipitation and Positive Temperature, already discussed. The value of an Ombrothermic Index is the quotient between Positive Precipitation and Positive Temperature of the considered period, multiplied by ten:

Io = (Pp/Tp) 10.

Certain intervals of Io reflect faithfully changes in biocenosis. The Ombrothermic Indexes are so determinant and significant that their intervals are used in all hierarchical levels of the Bioclimatic Classification of the Earth of Rivas-Martínez (2008) and Rivas-Martínez et al. (2011).

In addition to the Io, Annual Ombrothermic Index, many other Ombrothermic Indices can be calculated, for various periods that are considered significant, of 1, 2, 3, or more months.

In tropical territories, it is sometimes necessary to know the index:

Iod2     Ombrothermic Index of the driest bimester within the driest four-month period of the year.

Among the various Ombrothermic Indexes used in extratropical territories, the following are very significant:

Ios, Iosi        Ombrothermic Index of any month of the summer trimester (Tr3)

Ios1     Ombrothermic Index of the hottest month of the summer trimester (Tr3)

Ios2     Ombrothermic Index of the hottest bimester of the summer trimester (Tr3)

Iosc      Summer compensable Ombrothermic Indexes. Two of them are considered:

Iosc3 (= Ios3): Compensable Ombrothermic Index of the summer trimester (Tr3), necessary to evaluate the summer aridity

Iosc4 (= Ios4): Compensable Summer Ombrothermic Index for the four-month period resulting from adding, to the summer trimester (Tr3), the month immediately preceding. This index is also used to assess summer aridity.

All these Summer Ombrothermic Indexes are very important, since they measure the summer aridity and its possible compensation: They are essential to differentiate the Mediterranean Macrobioclimate, from the Temperate and Boreal Macrobioclimates (see these, sections 4.1.2, 4.1.3, and 4.1.4). For the correct use of all these Indexes, see chapter 9.

3.5.- Alphabetical list of the abbreviations that designate the Parameters and the Bioclimatic Indexes.

We have found it necessary to list, in alphabetical order, all the Parameters and Indices mentioned in the previous headings (See Figure 2).

Figure 2. Alphabetical list of Parameters and Bioclimatic Indexes acronyms.

Para-meter

/Index

Descripción

Ci

Continentality compensation value

Cm1

The warmest four-month period of the year.

Cm2

Four-month period following the Cm1

Cm3

Four-month period prior to the Cm1

Ic

Continentality / Oceanicity Index: Annual thermal amplitude.

Io

Annual Ombrothermal Index: (Pp/Tp) x 1O.

Iod2

Ombrothermal Index of the driest bimester within the driest four-month period of the year.

Ios, Iosi

Ombrothermal Index of any month of the summer trimester

Ios1

Ombrothermal Index of the hottest month of the summer trimester (Tr3)

Ios2

Ombrothermal Index of the hottest bimester of the summer trimester (Tr3)

Iosc

Summer compensable Ombrothermal Indexes

Iosc3(= Ios3)

Compensable Ombrothermic Index of the summer trimester, necessary to evaluate the summer aridity

Iosc4(= Ios4)

Compensable Summer Ombrothermal Index for the four-month period resulting from adding, to the summer trimester, the month immediately preceding. This index is also used to assess summer aridity.

It

Thermicity Index

Itc

Compensated Thermicity Index

M

Average temperature of the maximum temperatures of the coldest month in the year, ie, the month with the lowest Ti. (Seasonal Temperature Index)

m

Average temperature of the minimum temperatures of the coldest month in the year, that is, the month with the lowest Ti. (Seasonal Temperature Index)

mi

Average monthly temperature of the mínimum temperatures, where i: 1 = January, ..., 12 = December.

m´i

Average monthly temperature of absolute minimum temperatures, where i: 1 = January, ..., 12 = December

P

Annual precipitation

Pav

Period of plant physiological activity

Pcm1

Precipitation of the warmest four-month period of the year.

Pcm2

Precipitation of the four months period following the warmest four-month period of the year

Pcm3

Precipitation of the four months period previous to the warmest four months period of the year

Pf

Periods of frost

Pi

Monthly precipitation, where i: 1 = January, ..., 12 = December. (Weather parameter)

Pp

Annual Positive Precipitation

Pps

Positive Precipitation of the three warmest months period of the year (tropical zones), or of the summer trimester (extratropical zones).

Ppw

Positive Precipitation of the three coldest months period of the year (tropical zones), or of the winter trimester (extratropical zones).

Ps

Precipitation of the summer trimester

Psb1

Precipitation of the first two months after the summer solstice (July-August in latitude N, January-February in latitude S)

Psb2

Precipitation of the two subsequent months to Psb1 (September-October in latitude N, March-April in latitude S)

Psi

Monthly precipitation of any Summer month

Pss

Precipitation of the six warmest months of the year

Psw

Precipitation of the coldest six months of the year

PTr1

Precipitation of the winter solstice trimester

PTr2

Precipitation of the spring equinox trimester

PTr3

Precipitation of the summer solstice trimester

PTr4

Precipitation of the automn equinox trimester

Pw

Winter trimester precipitation

Ss

Warmer semester of the year

Sw

Warmer semester of the year

T

Average annual temperature. (Weather parameter)

Ti

Average monthly temperature, standing: 1 = January, ..., 12 = December. (Weather parameter)

Tmax

Average monthly temperature of the warmest month of the year.

Tmin

Average monthly temperature of the coldest month of the year.

Tp

Positive Annual Temperature

Tps

Positive Temperature of the warmest trimester of the year (Tropical Macrobioclimate), or summer trimester (Macrobioclimates extratropical)

Tpw

Positive Temperature of the coldest trimester of the year

Tr1

Winter solstice trimester

Tr2

Spring equinox trimester

Tr3

Summer solstice trimester

Tr4

Autumn equinox trimester

Tsi

Monthly Medium Temperature of any Summer month

>W>

Winter precipitation.

>P>

Spring precipitation.

>S>

Summer precipitation.

>F>

Fall precipitation.

 

 

4.- WORLDWIDE BIOCLIMATIC CLASSIFICATION

The Worldwide Bioclimatic Classification (Rivas-Mart, 2008, Rivas-Mart et al., 2011) is necessarily hierarchical, because it has to reflect the different range of influence of climatic factors on the distribution of life. The hierarchical bioclimatic units of the Classification are: 1-Macrobioclimates, 2-Bioclimates / Variants, and 3-Bioclimatic Belts.

Latitude has a decisive influence on the distribution of living beings and, for that reason, it is used in the first hierarchical step of classification, that of the Macrobioclimates. Indeed, latitude determines the photoperiod, the inclination of the sun's rays, the distribution of high and low atmospheric pressures, the general circulation of the atmosphere and its effect on the amount and distribution of rainfall, etc.,

Likewise, in each Macrobioclimate, the distribution patterns of the plant communities are governed by combinations of Continentality levels, together with humidity comfort levels: Ic and Io. Bioclimates and their variants are thus defined.

And in each Bioclimate / Variant unit, the combination of one level of ltc, -or of Tp - (Thermotype) with another of Io (Ombrotipo), reflects the actual distribution of vegetation types and, thus, define the third hierarchical level of the classification, the Bioclimatic Belts.

4.1.- First hierarchical level of the Classification: Macrobioclimates

4.2.- Second hierarchical level of the Classification: Bioclimates / Variants

4.3.- Third hierarchical level of the Classification: Bioclimatic Belts -Thermotypes and Ombrotypes-

 

4.1. First hierarchical level of the Classificacion: Macrobioclimates

The Macrobioclimates are the greater rank typological units of this Bioclimatic Classification. These are synthetic biophysical models, delimited by certain latitudinal and climatic values, that have a wide territorial jurisdiction and that are related to the great types of climates, biomes, and biogeographic regions, of the Earth. The five Macrobioclimates that are accepted in this classification are: Tropical, Mediterranean, Temperate, Boreal and Polar.

To distinguish the Macrobioclimates, the latitudinal values are the first to be taken into account, and their limits are shown in figure 3: Tropical Macrobioclimate fits the latitudinal warm zone (35 N & S); Mediterranean Macrobioclimate participates in the warm and temperate zones (23º-52º N & S); Temperate Macrobioclimate also participates in the warm zone and extends through almost all the temperate zone (23º-66ºN and 23º-55º S); Boreal Macrobioclimate is distributed throughout almost all the temperate zone and the cold zone, but has an asymmetric latitudinal distribution (42º-72º N and 49º-56º S); finally, the Polar Macrobioclimate is almost symmetrically distributed in the temperate zone and throughout the cold zone (51º-90ºN and 53º-90ºS).

Figure 3. Width of latitudinal zones and belts recognized on Earth, and their relationship to the distribution of Macrobioclimates. As can be seen, the limits of the Macrobioclimates do not coincide exactly with the corresponding belts, although they show close correspondences.

 

Latitudinal Zones

Latitudinal

Belts

Macrobioclimates

N

3. Cold

66º-90º

3a.

Arctic

66º-90º

 

 

 

 

 

 

Polar

 

51º-90º

 

 

 

Boreal

 

42º-72º

2. Temperate

35º-66º

2b. Subtemperate

51º-66º

Temperate

 

23º-66º

2a. Eutemperate

35º-51º

Medite-rranean

 

23º-52º

 

 

1. Warm

       0º-35º

1c. Subtropical

23º-35º

 

0º-35º

 

 

Tropical

 

 

0-35º

 

1b. Eutropical

7º-23º

 

 

1a. Equatorial

7ºN-7ºS

S

1. Warm

0º-35º

1b. Eutropical

7º-23º

1c. Subtropical

23º-35º

Medite-rranean

 

23º-52º

Temperate

 

23º-55º

2. Temperate

35º-66

2a. Eutemperate

35º-51º

 

Boreal

 

49º-56º

2b. Subtemperate

51º-66º

 

 

Polar

 

53º-90º

 

 

3. Cold

66º-90º

3a.

Antarctic

66º-90º

 

As shown in Figure 3, and despite their denominations, the boundaries of the Macrobioclimates do not correspond exactly to the Latitudinal Zones and Belts, but the comparison with them helps to locate the areas of each Macrobioclimate on the continents.

1.-In the latitudinal belts equatorial - 7ºN-7ºS - and eutropical - 7º-23ºN and S-, as the solar radiation is practically zenith and the duration of the day and of the night vary little along the year, the Macrobioclimate, at any altitude, regardless of temperature, is considered tropical.

2.- In the subtropical latitudinal belts - 23º-35º N and S -, depending on the temperature and the rhythm of the precipitations throughout the year, the territory is divided between the Tropical, Mediterranean and Temperate Macrobioclimates.

3.-In the eu-temperate latitudinal belts -35º-52ºN and S-, the seasonal photoperiods and the less energy received represent a severe border for plant and animal life, which have to adapt to drought and cold of the Mediterranean, Temperate or Boreal Macrobioclimates, depending on the rainfall rhythms and thermal levels.

4.-In the latitudinal subtemperate belts -52º-66ºN and 52º-60ºS-, the photoperiod and the thermicity establish new limits to the life, by the necessary adaptations to the intense photoperiod and the intense cold, typical of the Macrobioclimates Temperate, Boreal and Polar .

5.-In the latitudinal Arctic -66º-90ºN-and Antarctic -60º-90ºS- belts, due to the great difference in the duration of day and night, and the little thermal energy that is received during the solstices, life finds very severe limitations. Therefore, at any latitude and altitude, the Macrobioclimate is considered Polar.

In addition to the latitude, in the differentiation of the Macrobioclimas several thermal indices are used, in some cases related to the Continental Index, as well as certain rainfall rhythms. Thus, the Compensated Thermicity Index, Itc, which accurately measures the winter cold intensity - a true barrier for many living beings - is very discriminant to differentiate tropical, Mediterranean and temperate Macrobioclimates.

In the Earth's Bioclimatic Synopsis, Figure 7, in the Macrobioclimates column, we find all the necessary values to distinguish the Macrobioclimates from each other. Figure 4 is a copy of that first column of the Earth's Bioclimatic Synopsis, which facilitates its consultation.

Note: According to the Orobioclimates premise, to analyze the Macrobioclimate of a meteostation located at a certain height above sea level, it is necessary to theoretically calculate the thermal values that would have in its base, that is, between 0 and 200 meters above sea level. For that, it is necessary to increase T, M, Itc and Tp in certain values, for every 100 m that the weather station exceeds 200m. The amount of the increments vary somewhat with the latitude, so they are given, as a note, at the bottom of the summary table "Bioclimatic Synopsis of the Earth". (See Figure 7)

Figure 4.- Column of Macrobioclimates, extracted from the Bioclimatic Synopsis of the Earth

Macrobioclimates (1)

Name, Acronym and Differential Characters

Tropical    Tr

Warm Zone: Equatorial, Eutropical and Subtropical Belts (0º - 35º N & S). In Subtropical (23º - 35º N & S) at < 200 m, at least two values: T 25º, m 10º, Itc 580; or, if Pss > Psw, or Pcm2 < Pcm1 > Pcm3, at least two values: T 21º, M 18º, Itc 470. In Eurasia, from 25º to 35º N, height 2000 m: it is not tropical.

Mediterranean    Me

Subtropical Warm Zone (23º to 35º N & S) and Eutemperate Temperate Zone (35º to 52º N & S), with summer aridity at least bimonthly after the summer solstice: Ios2 2, Iosc4 2. In the Subtropical, at least two of the three thermal values: T < 25º, m < 10º, Itc < 580. 

Temperate     Te

Subtropical Warm Zone (23º to 35º N & S) and Temperate Zone (35º to 66º N & 35º a 54º S). Without summer aridity: Ios2>2, Iosc4>2. At <200 m, Tp380. Besides: a), from 23º to 35º N & S, at <200 m, at least two values: T<21º, M<18º, Itc<470; or b), against Boreal, at <200 m: if Ic11: T>6º, Tmax>10º and Tps>320; if 11<Ic21: Tp>720 and T>5.3º; if 21<Ic28:  Tp>740 and T>4.8º; if 28<Ic46: Tp>800 and T>3.8º; and if 46<Ic: Tp>800 and T>0º.

Boreal     Bo

Temperate and Cold Zones (42º to 72º N, 49º to 56º S). Without summer aridity: Ios2>2, Iosc4>2. At <200 m, Tp380. If Ic11: T6º, Tmax10º, 380Tp720 and Tps320; if 11<Ic21:  380Tp720 and T5.3º; if 21<Ic28: 380Tp740 and T4.8º; if 28<Ic46: 380Tp800 and T3,8; and if 46<Ic: 380Tp£800 and T0º.

Polar    Po

Temperate and Cold Zones (51º a 90º N & S).

Altitude < 100m: Tp < 380.

 

 (Rivas-Mart. et al., 2011)

(Modified M.L. López y M.S. López, 26 Dec. 2016)

(1) Between 23º - 48º N and 23º - 51º S, if the locality is 200 m, or more, of altitude, it is necessary to theoretically calculate the thermal values at such a height by increasing T by 0.6 °; M and m, by 0.5º; and Itc by 13 units, for every 100 m that exceeds said altitude. More than 48º N ó 51º S, it is necessary to calculate the theoretical values of the average annual temperature, of the average of the maximums temperature of the coldest month, and of the annual positive temperature, increasing T by 0.4º, M by 0.5º and Tp by 12 units, for every 100 m that exceeds said altitude.

 

4.1.1.- Tropical Macrobioclimate

The Tropical Macrobioclimate is distributed between latitudes 35º N & S, corresponding to the latitudinal belts equatorial, eutropical and subtropical, this last latitudinal belt, 23º-35º N and S, also occupied by the Mediterranean and Temperate Macrobioclimates. It should be remembered here the reciprocity premise, that in Eurasia, between 25º and 35º N and 70º-120º E, territories at 2,000m, or higher, are not tropical.

The territories with Tropical Macrobioclimate have very low Continentality, since the temperatures remain almost constant throughout the year. However, the ombric rhythms of the 6-months periods, or 4-months periods, are very important here, as well as a high level of certain thermal parameters and indices. (See Figure 4, or also, the Synopsis of the World Bioclimatic Classification, figure 7).

The optimum of vegetation in the Tropical Macrobioclimate is the rainforest, or equatorial forest, which is the terrestrial vegetation with the greatest biodiversity, structural complexity, biomass and productivity, with three or more layers of trees, with abundant woody lianas and numerous epiphytes. However, depending on the amount of precipitation, the structure of tropical potential vegetation corresponds to other types: semi-deciduous forests, open forests, shrub vegetation, semi-deserts, deserts, or hyper-deserts. In addition, the phytochenosis ruled by the Tropical Macrobioclimate have a very original flora and vegetation, rich and diverse, and, therefore, radically different from those of the territories with Mediterranean or Temperate Macrobioclimates, with precipitations of similar quantity.

The Tropical Macrobioclimate is present in all the continents, except in Antarctica.

 

4.1.2.- Mediterranean Macrobioclimate

The Mediterranean Macrobioclimate is distributed between the 23º-52º N & S, latitudes in which it coincides with the Tropical (23º-35º N & S), Temperate (23º-52º N & S) and Boreal (42º-52º N and 49º -52 S) Macrobioclimates. It should be remembered here the reciprocity premise, that in Eurasia, between 25º and 35º N and 70º-120º E, territories at 2,000m, or higher, are either Mediterranean or Temperate (not tropical).

Territories with a Mediterranean Macrobioclimate have a non-compensable summer aridity (see Chapter 9), ie, Ios2  2, with Iosc3  2, or Iosc4  2, in addition to a lower level than the Tropical in certain thermal Parameters and Indices. (See Figure 4, or also, the Synopsis of the World Bioclimatic Classification, figure 7).

The optimum of vegetation in the Mediterranean Macrobioclimate are the durisilva, sclerophyll forests of modest size, low biodiversity and productivity, with few lianas and almost no epiphytes. However, depending on the amount of rainfall, the structure of Mediterranean potential vegetation corresponds to very different types: further to durisilva, there are closed deciduous forests, conifer forests, shrub vegetation, semi-deserts, deserts or hyper-deserts. In addition, phytochenosis of the Macrobioclimate Mediterranean, have a very original flora and vegetation, rich and diverse, and, therefore, radically different from those of the territories with Tropical, Temperate, or Boreal Macrobioclimates, with precipitations of similar amount.

The Mediterranean Macrobioclimate has its greatest territorial representation in the center and in the western part of all continents, and does not exist in Antarctica.

 

4.1.3. Temperate Macrobioclimate    

Temperate Macrobioclimate is distributed between latitudes 23º to 66º N and 23º to 54º S, latitudes in which it coincides, in whole or in part, with the Tropical, Mediterranean and Boreal Macrobioclimates. The lack of summer aridity, by itself, distinguishes the Temperate Macrobioclimate of the Mediterranean Macrobioclimate, but, to distinguish it from the Tropical and the Boreal, it is necessary to specify well its thermal thresholds:

a)     Summer aridity: The Temperate Macrobioclimate, at any altitude and value of Continentallity, lacks summer aridity: that is, the two consecutive warmer months of the summer trimester (or warmer period of the year) have Ios2>2; or, if there were two arid months, with: Ios2  2, this aridity is compensated by the rains of the previous month, or of the previous two months: losc3>2, or losc4>2. (See Figure 4, or also the Synopsis of the World Bioclimatic Classification, figure 7).

b)    Thermal thresholds of Temperate Macrobioclimate in front of Tropical Macrobioclimate. Between 23º to 35º N & S, theoretically calculated at 200 m altitude, two of the three thermal values mentioned must meet the following conditions: T<2lº, M<l8º, ltc<470.

c)     Thermal thresholds of Temperate Macrobioclimate versus Boreal Macrobioclimate. Between 43º to 66º N and 49º to 54º S, values theoretically calculated at an altitude of 200 m, or those at lower altitudes, must be greater than the threshold values that limit Temperate and Boreal Macrobioclimates. Those thresholds, which depend on the Continentality Index values, can be seen in figure 4, or also in the Synopsis of the World Bioclimatic Classification, figure 7.

The optimum of vegetation in the Temperate Macrobioclimate are the evergreen laurisilva rich in arborescent ferns, as well as the deciduous aestisilva; in the cold extremes of the Temperate Macrobioclimate are characteristic the aciculisilvas; and, finally, in the xeric extremes of the Temperate Macrobioclimate, the deciduous woodland becomes discontinuous and easily transformed into extensive pastures, or steppes, under the pressure of grazing and of fires.

The Temperate Macrobioclimate is represented on all continents, except in Antarctica.

 

4.1.4.- Boreal Macrobioclimate  

The Boreal Macrobioclimate extends from latitudes 42º to 72º N and from 49º to 56º S, latitudes in which it coincides, to a greater or lesser extent, with the Mediterranean, Temperate and Polar Macrobioclimates. The following characteristics allow to define the Boreal Macrobioclimate and to differentiate it from the other three: the lack of summer aridity, by itself, distinguishes between Macrobioclimates Boreal and Mediterranean; the lower thermal threshold separates it from the Polar Macrobioclimate; but in order to distinguish it from the Temperate Macrobioclimate, its thermal thresholds must be well defined in dependance with Continentality.

a). - Lack of summer aridity. In the Boreal Macrobioclimate, at any altitude and value of Continentality, there are no two consecutive arid months during the summer or warmer period of the year; that is, Ios2>2; or, if there were two arid months, Ios2  2, these are compensated with Iosc3>2, or Iosc4>2. (See Chapter 9).

b). - Thermal thresholds of Boreal Macrobioclimate versus Temperate Macrobioclimate. Between latitudes 42º to 72º N and 49º to 56º S, thermo-climatic values theoretically calculated at an altitude of 200 m, or those at lower altitudes, must be lower than the threshold values between the Boreal and Temperate Macrobioclimates. Those thresholds, which depend on the Continentality Index values, can be seen in figure 4, or also in the Synopsis of the World Bioclimatic Classification, figure 7.

c). - Lower thermal threshold compared to Polar Macrobioclimate. The Boreal Macrobioclimate has a lower thermal threshold, calculated to less than 200 m, of Tp380. This threshold distinguishes it from the Polar Macrobioclimate.

The optimum of vegetation in the Macrobioclimate Boreal are acciculisilvas, conifer or taiga forests, with low understory but, at the thermal limits of the Macrobioclimate, the Tundra of nanofanerófitos, nanocaméfitos and hemicryptophytes appear.

The Boreal Macrobioclimate is represented in the continents of Eurasia, North America and South America, but is lacking in Africa, Australia and Antarctica.

4.1.5.- Polar Macrobioclimate

It is considered that all territories between the parallels 51º to 90º N & S, with a Positive Annual Temperature, theoretically calculated at 200 m altitude, lower than 380 (Tp <380), have a Polar Macrobioclimate. (See Figure 4, or also, the Synopsis of the World Bioclimatic Classification, figure 7).

The optimum of vegetation in the Macrobioclimate Polar are the nanofanerophytes and nanocamephytes tundras, and the graminoids lawns with more or less mosses and lichens, all of them communities of little productivity and slow growth.

The Polar Macrobioclimate is the only Macrobioclimate present in Antarctica and is also represented in the continents of Eurasia and North America, but it does not exist in Africa, South America or Australia.

4.1.6.- Macrobioclimates Continental Distribution

We show, in Figure 5, the continental distribution of Macrobioclimates.

 

Figure 5. Continental distribution of the Macrobioclimates

Continents / Macrobioclimates

North America

South America

Eurasia

Africa

Australia-Polynesia

Antarctica

Total, by

Continents

Tropical

+

+

+

+

+

---

5

Mediterranean

+

+

+

+

+

---

5

Temperate

+

+

+

+

+

---

5

Boreal

+

+

+

---

+

---

4

Polar

+

+ (Insular)

+

---

---

+

4

Total Macrobioclimates

5

5

5

3

4

1

 

 

 

4.2.- Second hierarchical level of the Classification: Bioclimates / Variants

Bioclimates constitute the second rank of the Rivas-Mart. (2008) and Rivas-Mart. & al. (2011) hierarchical Bioclimatic Classification.In the wide territories of each Macrobioclimate, life detects climate scenarios related to certain thresholds lo and lc, mainly, but also, in certain cases, with the precipitation rhythms (in the Tropical Macrobioclimate), or with the Tp (in Polar Macrobioclimate): those sets of climatic-environmental scenarios, indicated by changes vegetation, and subordinated to the Macrobioclimas, are the Bioclimates. 28 Bioclimates are recognized, distributed in the five Macrobioclimates. (See Synoptic Table, second column, figure 7). Each Bioclimate possesses vegetal formations, biomas, biocenosis and vegetal communities, of its own.

Regarding the Variants, in all the Bioclimates, certain peculiarities and variations of the seasonal rhythms of precipitation and / or temperature, tolerable within their defining intervals, allow to recognize the Bioclimatic Variants. Globally, nine Bioclimatic Variants are recognized.

Coming up next we will comment in detail: in 4.2.1, the distinguishable Bioclimates within each Macrobioclimate; and in 4.2.2, the recognized Bioclimatic Variants, their peculiarities, and the Bioclimates to which they affect:

4.2.- Second hierarchical level of the Classification: Bioclimates / Variants

4.2.1. Bioclimates

4.2.1.a) Tropical Bioclimates

4.2.1.b) Mediterranean Bioclimates

4.2.1.c) Temperate Bioclimates

4.2.1.d) Boreal Bioclimates

4.2.1.e) Polar Bioclimates

4.2.2.- Bioclimatic Variants

4.2.2.a) Pluviserotin Variant (Pse).

4.2.2.b) Antitropical Variant (Ant).

4.2.2.c) Bixeric Variant (Bix).

4.2.2.d) Tropical Drought Variants (Str).

4.2.2.e) Semitropical Hyperdesertic Variant (Strhd).

4.2.2.f) Steppic Variant (Stp).

4.2.2.g) Submediterranean Variant (Sbm).

4.2.2.h) Polar Semiboreal Variant (Pose).

4.2.2.i) Normal Variant (Nor).

 

4.2.1. Bioclimates

In the Tropical Macrobioclimate, which maintains a very constant temperature throughout the year, the amount and the seasonal rhythm of the precipitations are the criteria that delimit its Bioclimates. In the rest of the Macrobioclimates there are already seasonal variations, both rainfall and temperature, throughout the year, so that, in addition to the humidity comfort - Ombrothermal Index, lo-, also the annual thermal amplitude - Continentality Index, lc -, differentiate bioclimatic ambits. However, in the Mediterranean Macrobioclimate, with summer aridity, in which by definition water acts as a limiting factor of life, especially during summer, the vegetation perceives up to four levels of Io and two levels of Ic. As for Temperate, Boreal and Polar Macrobioclimates, without summer aridity, the most discriminating factor for life is the annual thermal amplitude -lc-, followed in importance by the humidity comfort -lo-: the vegetation itself marks three levels of Ic in the Temperate and Polar Macrobioclimates, and five levels in the Boreal Macrobioclimate; while, with respect to lo, the vegetation only distinguishes two levels in all the three Macrobioclimates.

4.2.1.a) Tropical Bioclimates

Within the vast territories occupied by the Tropical Macrobioclimate, five Bioclimas are recognized, which correspond with the five large caesuras, related to both the annual Ombrothermal Index, Io, and the rainfall regime, Iod2. (See figure 7, Synopsis of the Worldwide Bioclimatic Classification).

Thus, the tropical bioclimatic space distinguishes three thresholds of Io, delimiting four intervals, in the wettest of which, the rainfall regime, Iod2, separates, in turn, two other intervals: in total, five Bioclimates The threethreshold values of Io are: 3.6, 1.0 and 0.2, and the threshold value of Iod2 is 2.5. The five Tropical Bioclimates are thus defined: Tropical Pluvial, with Io ≥3,6 and Iod2> 2,5; Tropical Pluviseasonal, with Io ≥3,6 and Iod2≤2,5; Tropical Xeric, with 1.0lo<3,6; Tropical Desertic, with 0,2lo<1,0; and Tropical Hyperdesertic, with Io <0.2.

The optimum of vegetation in each of the Tropical Bioclimates are the following formations: in the Tropical Pluvial, the rainforests; In the Tropical Pluviseasonal, the hiemisilva; in the Tropical Xeric, the open hyemifruticeta in mixture with the terriherbosa; in the Tropical Desertic, the sicidesertas; and in the Tropical Hyperdesertic, the absence of rooted vascular plants, since they are regions without vascular plants.

4.2.1.b) Mediterranean Bioclimates

In the territories of Mediterranean Macrobioclimate, located in the center and in the western façades of the continents, eight Mediterranean Bioclimates are recognized, which correspond to as many changes in vegetation, and which are related to the combination of four levels of humidity comfort -lo-, with two levels of Continentality -lc-. (See figure 7, Synopsis of the Worldwide Bioclimatic Classification).

And so, in the Mediterranean Macrobioclimate, life distinguishes three thresholds of Io, delimiting the following four intervals of humidity comfort: with 2.0lo, two Mediterranean Pluviseasonal Bioclimates; with 1.0lo < 2, two Mediterranean Xeric Bioclimates; with 0.2lo < 1.0, two Mediterranean Desertic Bioclimates; and with lo<0.2, two Mediterranean Hyperdesertic Bioclimates. At each of those four intervals, two levels of Continentality can be recognized: with lc21, four Mediterranean Oceanic Bioclimates; with lc>21, four Mediterranean Continental Bioclimates. The eight Mediterranean Bioclimates are thus characterized: Mediterranean Pluviestacional Oceanic, Me. Pluviestacional Continental, Me. Xeric Oceanic, Me. Xeric Continental, Me. Desert Oceanic, Me. Desert Continental, Me. Hyperdesertic Oceanic and Me. Hyperdesertic Continental.

The optimum of vegetation in each of the Mediterranean Bioclimates are the following formations: in the Pluviestational Mediterranean Bioclimates, the optimum of vegetation are sclerophyllous forests and, to a lesser extent, laurifolia semipervirent forests, deciduous forests and needle-leaves forests; in the Xeric Mediterranean Bioclimates, the optimum of vegetation are closed microforests and shrubs; in the Mediterranean Desertic Bioclimates, the optimum of vegetation are semi-deserts, open shrubs and scatered thickets; and in the Hyperdesertic Mediterranean Bioclimates, the characteristic feature is the absence of climatophile woody vegetation.

4.2.1.c) Temperate Bioclimates

In Temperate Macrobioclimate life distinguishes two intervals of humidity comfort: thus, with lo3.6, Xeric Temperate Bioclimate, and with lo>3.6, three Bioclimates, distinguishable by two Continentality thresholds, 11 and 21: with lc11, Hypercoceanic Temperate Bioclimate; with 11<lc21, Oceanic Temperate Bioclimate; and with Ic>21, Continental Temperate Bioclimate. In this way, four Bioclimas have been recognized within the Temperate Macrobioclimate. (See figure 7, Synopsis of the Worldwide Bioclimatic Classification).

The optimum of vegetation in each of the Temperate Bioclimates are: in the Hyperoceanic Temperate Bioclimate, the optimum of vegetation are the lauroid forests; in the Oceanic Temperate and Continental Temperate Bioclimates, the optimum of vegetation are the winter deciduous forests, as well as, in the mountains, conifer forests; and in the Xeric Temperate Bioclimate the optimum of vegetation are the laurifruticeta and the aestifruticeta.

4.2.1.d) Boreal Bioclimates

In the Boreal Macrobioclimate territories, six Bioclimates are recognized, characterized by their levels of Continentality, in combination with the Ombrothermal Index. In this Macrobioclimate, life has great sensitivity to Continentality, recognizing four thresholds that delimit five intervals: lc11, 11<lc21, 21<lc28, 28<lc46, 46<lc. With respect to Io, only two intervals, separated by a threshold, are recognized: : lo>3.6, or lo3.6 (See figure 7, Synopsis of the Worldwide Bioclimatic Classification).

So, when Continentality is extremely high, lc>46, the Bioclimate is Boreal Hypercontinental, regardless of the Ombrothermal Index of the place. However, with Continentality Index below 46, Ic46, if the Ombrothermic Index is less than, or equal to, 3.6 -lo 3.6-, the Bioclimate is Boreal Xeric; But if the Ombrothermic Index is greater than 3.6 -lo>3.6-, the Bioclimate goes in function of the lc, as follows: with lc11, Boreal Hiperoceanic Bioclimate; with Ic between 11 y 21 -11<lc2l-, Boreal Oceánico Bioclimate; with Ic between 21 y 28 -2l<lc 28-, Boreal Subcontinental Bioclimate; and if Ic between 28 y 46 -28<lc46-, Boreal Continental Bioclimate.

The optimum vegetation in the Boreal Bioclimates are coniferous forests, and shrub and Ericaceae tundra.

4.2.1.e) Polar Bioclimates                                       

In the territories with Polar Macrobioclimate, due to the intrinsic difficulties that represent the low temperatures, life distinguishes: in addition to a threshold and two ranges of Positive Temperature -Tp =0, or Tp>0-, two thresholds and three intervals of Continentality, -Ic : 11 y 21-, as well as one threshold and two intervals of Io, -3,6-, thus defining, in total, five Bioclimates: Polar Hyperoceanic, Polar Oceanic, Polar Continental, Polar Xeric and Polar Pergelid (See figure 7, Synopsis of the Worldwide Bioclimatic Classification).

The optimum vegetation in the Boreal Bioclimates are coniferous forests, and shrub and Ericaceae tundra.

 

4.2.2.- Bioclimatic Variants

The amplitude of the intervals defining each Bioclimate, allows certain variations in the rhythms of humidity and/or temperature (such as advance / delay of rains, or of high / low temperatures). The vegetation reflects these variations, which are bioclimatically expressed by the Variants.

In the set of five Macrobioclimates, nine Bioclimatic Variants have been recognized (See Figure 6). (It should be noted that the Variant of Tropical Drought includes, in fact, seven Variants):

Pluviserotin (late-summer rains), Antitropical, Bixeric (two droughts), Tropical Drought, Semitropical Hyperdesertic, Steppic, Submediterranean, Polar Semiboreal, and Normal.

4.2.2.a) Pluviserotin Variant (Pse). Tropical Bioclimatic Variant in which the precipitation of the first two months of the summer solstice (June-July, in latitudes N, and December-January, in latitudes S) is less than 1.3 times that corresponding to the two months that follow (August-September in latitudes N, and February-March, in latitudes S): Psb1<l.3Psb2. This Variante does not take place in either the Tropical Pluvial Bioclimate or the Tropical Hyperdesertic Bioclimate.

This Bioclimatic Variant is due to the monsoon activity that, in Africa, Indostan and North America, delays the summer rains until the autumn. Its plant communities have the same structure as the normal tropical ones with equivalent Ombrotype, although their floristic element differs, due to the phenological isolation.

4.2.2.b) Antitropical Variant (Ant). Tropical Bioclimatic Variant, practically restricted to the equatorial waist and adjacent territories, where rainfall corresponding to the winter solstice trimester (December, January and February, in latitude N, and June, July and August, in latitude S) are higher than those of the summer trimester (June, July and August, in latitude N, and December, January and February, in latitude S): PTr1>PTr3. This Variant does not take place in either the Tropical Pluvial Bioclimate or the Tropical Hyperdesertic Bioclimate.

The Antitropical plant formations are very similar, in their structure, to those of the Tropical Pluviserotin Variant and of the Normal Variant, with equivalent Ombrotype, although their floristic element has a high number of endemisms, obviously caused by a phenological period practically antithetical, which has favored their isolation and, therefore, their speciation

4.2.2.c) Bixeric Variant (Bix). Tropical Bioclimatic Variant, in which there are two annual periods of aridity, with at least one month of P2T, in both solstices, separated by two more rainy periods in both equinoxes, in which at least one month is P>2T. This Variant does not take place in either the Tropical Pluvial Bioclimate or the Tropical Hyperdesertic Bioclimate.

The Bixeric Tropical plant formations have structural, and sometimes phylogenetic, relationships with those Mediterranean pluviestational, xeric and desertic.

Figure 6. Distribution of the Bioclimatic Variants in the Macrobioclimates of the Earth. Tr = Tropical, Me = Mediterranean; Te = Temperate; Bo = Boreal; And Po = Polar. (According to Rivas-Mart et al., 2011, modified by the authors).

Bioclimatic Variants

("drought" levels)

Tr

Me

Te

Bo

Po

Pluviserotin (Pse)

 

 

 

 

 

Antitropical (Ant)

 

 

 

 

 

Bixeric (Bix)

 

 

 

 

 

Tropical Drought (Str),

(7 Humidity-Variants of)

Pluvial Hygrophytic

 

 

 

 

Pluvial Subhigrophytic

 

 

 

 

Pluvial Submesophytic

 

 

 

 

Pluviseasonal Mesophytic

 

 

 

 

Pluviseasonal Submesophytic

 

 

 

 

Pluviseasonal Subxerophytic

 

 

 

 

Pluviseasonal Xerophytic

 

 

 

 

Semitropical Hyperdesertic (Strhd)

 

 

 

 

 

Steppic (Stp)

 

 

Submediterranean (Sbm)

 

 

 

Polar Semiboreal (Pose)

 

 

 

 

 

Normal (Nor)

 

 

4.2.2.d) Tropical Drought Variants (Str). Bioclimatic Variants that operate in the Tropical Pluvial and Tropical Pluviestational Bioclimes, when the monthly Io, in one or several months, is lower than 2.5, circumstance that gives rise to a period, more or less prolonged and / or more or less intense, of relative drought. Three Variants ("drought" levels) are recognized in the Tropical Pluvial Bioclimate, and four other Variants in the Pluviseasonal Tropical Bioclimate. (Figure 6). (For more information, see Rivas-Mart et al., 2011, pp. 15).

4.2.2.e) Semitropical Hyperdesertic Variant (Strhd). In the subtropical latitudinal zone (23º-35º N & S), a territory of Mediterranean Macrobioclimate and Ombrotype from Hyperarid to Ultrahyperarid (Io = 0.0 - 0.4) should be considered as a Hyperdesertic Semitropical Variant, when the trimester precipitation corresponding to the solstice of Summer (Tr3) is only 0.7 times lower than the winter solstice trimester (Tr1) precipitation: PTr3 <0.7 PTr1. This occurs in the hottest deserts of California, in North America, in the deserts of Antofagasta or Atacama in South America, and in the deserts of the oceanic Sahara and Namibia in Africa. (For more information, see Rivas-Mart et al., 2011, pp. 15).

4.2.2.f) Steppic Variant (Stp). Steppicity is a bioclimatic characteristic that, in the extratropical Macrobioclimates (Mediterranean, Temperate, Boreal and Polar), indicates the existence of two breakes off (or pauses) in the vital activity during both  solstices, in summer (June, July and August, in latitudes N, And December, January and February, in latitudes S) and in winter (December, January and February, in latitudes N, and June, July and August, in latitudes S), due to drought and/or cold.The steppic character only appears in Bioclimates with tendencies to drought and to Continentality, and is emphasized by the appearance of xerophytic types of vegetation, due to the water limitation and / or the low temperatures, existing in both solstices.

For the Steppic Variant to appear, the Bioclimate must have a lc at least of Semicontinentality, lc> l7, and a Io low, between the Lower Hyperarid and the Upper Sub-humid, 6.0≥lo>0.2. The brakes on vegetative activity, characteristic of the Steppic Variant, imply the following: a), The braking of the steppic summer requires at least one month of summer whith the precipitation, in mm, less than three times its temperature, in degrees centigrade: Psi < 3Tsi; b), The braking of the steppic winter is recognized because the positive precipitation of the summer trimester is higher to the positive precipitation of the winter trimester: Pps>Ppw.

The steppic character is highlighted in very diverse continental or semicontinental plant formations, due to the appearance of types of xerophytic vegetation, as well as for the fragility of the forests, due to the water limitation existing in both solstices. The most characteristic steppic plant formations of the Earth, corresponding to this Bioclimatic Variant, are: the micro-forests, shrubland and Mediterranean xeric steppe grasslands of the Northern Hemisphere; the steppes and temperate steppic forests of Eurasia; the broad grasslands, wooded or not, of North America; and also the taiga and tundra steppic formations, boreal and polar, restricted to areas of low summer precipitation, in Asia and North America.

4.2.2.g) Submediterranean Variant (Sbm). Bioclimatic variant frequent in Temperate Macrobioclimate, and scarce in Boreal and Polar Macrobioclimates, in which, at least during one summer month (June, July or August, in latitudes N, and December, January or February, in latitudes S), the precipitation in millimeters is less than two and eight tenths the average temperature in degrees centigrade of that same period:  Iosi <2.8, or Psi<2.8Tsi

The most characteristic submediterranean temperate plant formations are those of transition or ecotone between Temperate Bioclimates, lacking summer aridity, and the genuinely Mediterranean, where the summer drought lasts for at least two months. In the Hollartic Kingdom, the most representative plant formations are usually those formed, in the mature stage, by sclerophyllous or deciduous forests, as well as certain types of xerophytic coniferous forests and xerophytic tundra.

4.2.2.h) Polar Semiboreal Variant (Pose). A Boreal Macrobioclimate territory, with Ic28 -Bioclimates Boreal Hyper-oceanic, Boreal Oceanic and Boreal Subcontinental-, and Termotype Oroboreal,  Tp  between 380-480, should be considered as a Polar Semiboreal variant, if it is a mountain completely surrounded by forest at its base and, in addition, the Tmax11º (average monthly temperature of the warmest month of the year) and Tps320 (positive temperature of the summer trimester, in tenths of degree), since the natural potential vegetation in these bioclimatic conditions are deforested tundras, instead of micro-forests: that is the case in North America - on the western shores and reliefs of the Alaska Peninsula towards the Bering Strait, or on the Aleutian Peninsula and Islands -, and in other artoboreal and antiboreal territories of the Earth. (For more information, see Rivas-Mart et al., 2011, pp. 15).

4.2.2.i) Normal Variant (Nor). In this hierarchical level "Bioclimate / Variant", the portion of a Bioclima that does not present any of the thermal or ombric peculiarities of any of the other eight variants described above, is considered to have Normal Variant. It is essential to name as Normal Variant the rest of the Bioclima not included in any of the other eight Variants, because   using the name of the Bioclima for both the Bioclima and for what remains after assigning Variant to some parts of it, would be a cause of confusion, especially when making Bioclimatic Maps (because we would be giving the same name to two different hierarchical levels). So the Normal Variant occurs in all of the Bioclimates, alone or accompanied by one or more of the other Variants, except in the Tropical Pluvial and Tropical Pluviseasonal. (See Figure 6).

 

4.3.- Third hierarchical level of the Classification: Bioclimatic Belts -Thermotypes and Ombrotypes-

Bioclimatic Belts are each one of the environments that follow each other in a latitudinal, longitudinal or altitudinal cliserie. Each Bioclimatic Belt is defined by a thermal interval together with a humidity comfort interval: that is, by a Thermotype and a Ombrotype. Each Bioclimatic Belt corresponds to certain formations and plant communities: a vegetation belt. The phenomenon of plant zoning has universal jurisdiction. The Thermotypic threshold values (Itc, Tp) differ somewhat from one Macrobioclimate to another (see figure 7, Bioclimatic Belts, column 3), but Ombroclimatic threshold values (Io) are the same in all Macrobioclimates (see figure 7: Bioclimatic Belts, column 4).

Sometimes it is convenient to distinguish, within the Bioclimatic Belts, the lower and upper halves of their thermal and ombric intervals: thus appear the subordinate units of Bioclimatic belts, the so-called Bioclimatic Horizons, Termotypic and Ombrotypic. Bioclimatic Horizons are named by adding the word "lower" or "upper" to the corresponding name of the Thermotype or the Ombrotype: Upper Termomediterranean Horizon; Lower Subhumid Horizon.

Expressing the Thermotypes and the Ombrotypes as Belts, or as Horizons, depends on the territorial scale to which we work.

Explanatory note:

It is important to remark a peculiarity in the names of the Termotypic Horizons: the upper / lower adjectives refer to the actual values of thermal comfort (Thermotypes), precisely to the hotter half, or cooler half, of the thermal belt. But it is necessary to take into account that, in Nature, the upper thermal Horizon, hotter, is found, paradoxically, at the lower height. So, in nature, and contrary to what their names indicate, the higher, hotter Horizon is situated at a lower altitude than the lower, colder Horizon, which stands higher.

4.3.1.- Thermotypes. These are thermal categories of the climate, which take into account certain intervals of Itc and / or Tp, and that occurring in latitudinal, longitudinal or altitudinal sequence -thermobelts - in each of the Macrobioclimates of the Earth. Generally speaking, seven thermobelts are recognized: Infra-, Thermo-, Meso-, Supra-, Oro-, Crioro- and Gelid-, although not all seven are recognized in each Macrobioclimate. Besides, as thermo-threshold values vary slightly from one Macrobioclimate to another, the Thermotypes of each Macrobioclimate need to be named by adding, to the general word that indicates the belt, the name of the Macrobioclimate itself: Termotropical, Suprapolar, etc. Thus, the Thermotypes recognized in the Bioclimatic Classification of the Earth amount to 31. In the fourth and fifth column -Thermotypes- of the table "Bioclimatic Synopsis of the Earth" (Figure 7), the names of all the Thermotypes in each Macrobioclimate, and the intervals of Itc and Tp that delimit them in each Macrobioclimate, are indicated, as well as the acronyms that designate them. At any altitude, or latitude, when the Thermicity Compensated Index (Itc) is lower than 120, or when the Continentality Index (Ic) is equal to or higher than 21, to recognize the Thermotype, the value of the Annual Positive Temperature (Tp) is used.

To express the Upper and Lower Horizons of each Thermotype, the upper / lower words are added to the Thermotype name, or the letters "s" or "i", to the corresponding acronym. Thus, for example: Upper Mesomediterranean Horizon - Mmes; Lower Mesomediterranean Horizon - Mmei. (Thermo-Horizons are not recognized in the Gelid Thermotypes or the Infratemperate Thermotype).

4.3.2.- Ombrotypes. They are climate categories, which express the level of humidity comfort, or discomfort, through intervals of the Annual Ombrothermal Index, lo. The Ombrotyps follow each other in the latitudinal, longitudinal or altitudinal sequence - ombro-belts - in each of the Macrobioclimates of the Earth. Given the high predictive value and the high correlation that the annual ombrothermal values show with the climatophilic potential vegetation structures in the whole Earth, Rivas-Martínez & al. (2011) have used humidity confort intervals to establish their Омбрotypes.

The Ombrotypes recognized in the Bioclimatic Classification of the Earth are the following nine: Ultrahyperarid, Hyperarid, Arid, Semi-arid, Dry, Sub-humid, Humid, Hyper-humid and Ultrahyper-humid. The threshold values that diagnose the Ombrotypes are always the same in all Macrobioclimates and their intervals, as well as the abbreviations abbreviations that designate them, are shown in the fourth column - Ombrotypes- of the table "Bioclimatic Synopsis of the Earth" (see figure 7).

To express the Upper and Lower Horizons of each Ombrotype, the upper / lower / lower word is added to the Ombrotype name, or the letters "s" or "i", to the corresponding acronym. Thus, for example: Upper Dry Horizon – Drys/Secs; Lower Dry Horizon - Dryi/Seci.

 

5.- BIOCLIMATIC SYNOPSIS OF THE EARTH

It is a table, compacted  into  a  page, that summarizes  the  whole  of  the  Bioclimatic world hierarchical Classification, with an indication of the characters and thresholds that distinguish each one of its three levels: Macrobioclimates, Bioclimates / Variants (these only mentioned), and Bioclimatic Belts. (See Figure 7).

Figure 7: Bioclimatic Synopsis of the Earth. (Link to its quality file).

 

6.- ISOBIOCLIMATE

An Isobioclimate is a unique bioclimatic space, defined by a Bioclimate / Variant, together with a Bioclimatic Belt - Thermotype + Ombrotype-. Each Isobioclimate is an elemental bioclimatic unit, as perceived and distinguished by living beings. We can consider each Isobioclimate as a natural culture chamber, a Phytotron, whose "walls" are the lower and upper thresholds that define each one of its components: Macrobioclimate, Bioclimate / Variant and Bioclimatic Belt-Thermotype and Ombrotype-. Considering fixed other environmental variables - such as mother rock, soil, geological history, evolutionary history of living beings, etc. - each Isobioclimate harbors, in a climax position, a single vegetation series.

Isobioclimates are useful for identifying bioclimatically analogous territories on any of the five Continents, as well as for recognizing equivalent types of vegetation. The representation on the map of the areas occupied by each Isobioclima allows very precise bioclimatic maps to be obtained. (See figure 116, Isobioclimatic Map of Peninsular Spain).

To name each Isobioclimate is used a phrase that includes: Bioclimate / Bioclimatic Variant, together with a Bioclimatic Belt - Thermotype + Ombrotype-. Thus, for example: Mepo Nor Tme Dry is the Isobioclimate "Mediterranean Pluviseasonal Oceanic, Normal Variant, Thermomediterranean, Dry", which is found, for example, in much of Andalusia, Spain; or Boxe Stp Tbo Dry is the Isobioclimate "Boreal Xeric Steppic, Termoboreal, Dry", which operates, for example, in Petropavlovsk, Kazakhstan.

 

7.- BIOCLIMOGRAMS

Bioclimograms, also called Bioclimographs, or Ombro-Termoclimograms, are the graphical representation of Isobioclimates. Bioclimograms used by Rivas-Martínez (2008) and Rivas-Martínez & al. (2011), are based on those of Gaussen & Bagnouls (1952) and also on those of Walter & Lieth (1967). These graphs, very expressive, represent, in a Cartesian coordinate system with two ordinates and one abscissa, the temperature and rainfall data of a meteorological station, throughout the year. In the left ordinate, the temperature is represented, and in the right ordinate, the rainfall: their scales are adjusted to the ratio 2T (ºC) = P (mm). On the abscissa, the months of the year are represented: in the first place appears the month following the winter solstice: January in the Northern Hemisphere, and July in the Southern Hemisphere.

The graph of Figure 8 is accompanied by a data panel, which includes:

name of the station (1); its altitude in meters (2); its latitude, longitude, and the number of years of meteorological observations (3); P (4), T (5), m (6), Ic (7), M (8), Tp (9), Itc (10), Tn (11), Io (12); trimesterly precipitation in decreasing order (13): Pn=spring, S=summer, F=automn, and W=winter; M '(14); m' (15); temperature scale (16); precipitation scale (17).

 

Figure 8.- Structure of the Bioclimogram (Rivas-Mart, 2008, Rivas-Mart et al., 2011, somewhat modified by the authors). (Explanation of numbers, in the text).

In order to accommodate, in a single type of Bioclimograma, all the variations of Ti and Pi occurring in the world, the temperature scale (16) starts at zero on the dotted line and advances five degrees by five degrees above zero; with respect to negative temperatures, the scale is modified and each interval represents the following temperatures: -10, -20 y – 60ºC. As for the precipitations (17), each segment represents 10mm of rainfall until reaching 90mm, because, from this rainfall, the values are doubled for each interval: 180, 360 y 720mm of Pi (18). The surface of the rainfall curve, that exceeds the 90 mm line, is colored in blue (18) (in this diagram we have put it in yellow), to indicate the change of scale. When the temperature curve exceeds that of the precipitation, the area enclosed between the two curves, drought expression (19), is colored red (in this scheme we have put it in blue); But, if the rainfall curve exceeds that of the temperature, that surface is striped, to indicate period with available humidity (20). Monthly frost periods: sure or probable (21); and absent (22). The period of plant activity, Pav, (23): months with Ti ≥ 3,5 °; NORTH HEMISPHERE: months in the Northern Hemisphere, and HEMISPHERE SUR: months in the Southern Hemisphere: E, January; ...; X, July; ...; (24): at the bottom of the graph, the complete bioclimatic diagnosis, the Isobioclimate, -including Macrobioclimate (named in the Bioclimate), Bioclimate, Bioclimatic Variant and Bioclimatic Belt, expressed as Thermotype and Ombrotype horizons-, is given.

 

8.- APPROACH to the GLOBAL BIOCLIMATIC DIVERSITY

Global Bioclimatic Diversity can be considered at each of the three hierarchical levels of the World Bioclimatic Classification:

8.1.- At the first hierarchical level, that of the Macrobioclimates, total World Diversity is 5 Macrobioclimates.

8.2.- For the second hierarchical level, that of the Bioclimates/Variants, we have collected, in figure 9, almost the whole totality of the World Diversity at this level, 74 Bioclimate / Variant units, distributed by Bioclimates and by Variants.

As for Macrobioclimates, at this Bioclimate / Variant level, the most diversified is the Tropical Macrobioclimate, with 18 Bioclimate/Variant units, followed by the Boreal Macrobioclimate, with 17. By variants, the best represented are: the Normal Variant, which is present in each Bioclimate, except in Tropical Pluvial and Tropical Pluviseasonal; the Steppic Variant, present in 18 of the Bioclimates; and the Submediterranean Variant, present in 15 Bioclimates.

8.3.- And, in the third hierarchical level, that of the Bioclimatic Belts -Thermotypes and Ombrotypes-,the World Bioclimatic Diversity, at this level of Isobioclimates, is almost 400 Isobioclimates, although only about 300 Isobioclimates have a significant territorial entity worldwide. (Rivas-Mart. & Rivas-Sáenz, 1996-2017; Rivas-Mart. et al., 2011).

Figure 10 lists, for each Macrobioclimate, the number of its Bioclimates, its Variants, its combined units Bioclimate + Variant, and of the Thermotypes and Ombrotypes that operate in it. And, in its last column, appears the approximate number of its Isobioclimates

The world 's largest bioclimatic diversity, at Isobioclimates level, is offered by Temperate Macrobioclimate, with more than 97 Isobioclimates, followed by Tropical Macrobioclimate, with more than 91.

Figure 9.- Almost all the possible combinations of Bioclimate / Variant, in the 28 Bioclimates, of the five Macrobioclimates, distributed by Bioclimates and by Variants.

Bioclimates

Pse

Ant

Bix

Str

Stp

Sbm

Nor

Total

Total

Trpl

 

 

 

Pluvial Hygrophytic

 

 

 

3

 

Pluvial Subhigrophytic

Pluvial Submesophytic

Trps

Pluviseasonal Mesophytic

 

 

 

7

 

Pluviseasonal Submesophytic

Pluviseasonal Subxerophytic

Pluviseasonal Xerophytic

Trxe

 

 

 

4

 

­Trde

 

 

 

 

3

 

Trhd

 

 

 

 

 

 

1

 

Total Tropical

 

 

 

 

 

 

 

 

18

Mepo

 

 

 

 

 

2

 

Mepc

 

 

 

 

 

2

 

Mexo

 

 

 

 

 

2

 

Mexc

 

 

 

 

 

2

 

Medo

 

 

 

 

 

2

 

Medc

 

 

 

 

 

2

 

Meho

 

 

 

 

 

 

1

 

Mehc

 

 

 

 

 

 

1

 

Total Mediterranean

 

 

 

 

 

 

 

 

14

Teho

 

 

 

 

 

2

 

Teoc

 

 

 

 

3

 

Teco

 

 

 

 

3

 

Texe

 

 

 

 

3

 

Total Temperate

 

 

 

 

 

 

 

 

11

Boho

 

 

 

 

 

2

 

Booc

 

 

 

 

3

 

Bosc

 

 

 

 

3

 

Boco

 

 

 

 

3

 

Bohc

 

 

 

 

3

 

Boxe

 

 

 

 

3

 

Total Boreal

 

 

 

 

 

 

 

 

17

Poho

 

 

 

 

 

2

 

Pooc

 

 

 

 

3

 

Poco

 

 

 

 

3

 

Poxe

 

 

 

 

3

 

Popg

 

 

 

 

3

 

Total Polar

 

 

 

 

 

 

 

 

14

TOTAL

3

3

2

7

18

15

26

74

74

 

 

Figure 10.- The almost totality of World Bioclimatic Diversity at Isobioclimates level.

Macro-bioclimate

Bio-climates

Operating Variants

Bioclimates +

Variants

Operating Thermo-types

Operating Ombro-types

Isobio-climates

Tropical

5

11

18

7

9

Más de 91

Mediterra-nean

8

2

14

7

9

Más de 68

Temperate

4

3

11

7

6

Más de 97

Boreal

6

3

17

6

6

Más de 66

Polar

5

3

14

4

6

Más de 29

Total

28

13 in the world

74

31

9 in the world

Almost    400

 

 

8.4.- As illustrative examples of World Bioclimatic Diversity, next we give 59 climatic-bioclimatic examples, from as many meteorological stations, which represent the majority of the existing combinations of Macrobioclimate, Bioclimate and Bioclimatic Variant. Moreover, this information is available in: Worldwide Bioclimatic Classification System, 1996-2017, S. Rivas-Martínez & S. Rivas-Sáenz, Phytosociological Research Center, Spain, http://www.globalbioclimatics.org. In order to facilitate access to those examples, in Figure 11 we give the list of the 59 selected stations, ordered according to the Bioclimatic Synopsis of the Earth (see Figure 7, Chapter 5); and in figure 12, the list of those same selected stations, sorted alphabetically by country. After the figures 11 and 12, appear each of the climatic-bioclimatic examples, ordered by Bioclimate / Variant, figures 13-71.

 

Figure 11.- List of climate-bioclimatic representative examples of almost every combination of Macrobioclimate and Bioclimate / Bioclimatic Variant, with territorial representation on Earth, in bioclimatic order.

 

Bioclimate / Variant

Country

Weather Station

1

Trpl Hygrophytic

Japan

Ishigaki

2

Trpl Subhigrophytic

Suriname

Zanderij

3

Trpl Submesophytic

China

Wucho/Tsang-Wu

4

Trps Mesophytic

Indonesia

Achmad Yani

5

Trps Submesophytic

Bahamas Islands

Nassau Intl

6

Trps Subxerophytic

Madagascar

Tananarive

7

Trps Xerophytic

Mexico

Zapopán

8

Trps Pse

Vietnam

Donghoi

9

Trps Ant

Sri Lanka

Trincomalee

10

Trps Bix

Ivory Coast

Port Bouet

11

Trxe Pse

Chad

Ati

12

Trxe Ant

Saudi Arabia

Khamis Mushait

13

Trxe Bix

Ethiopia

Diredawa

14

Trxe Normal

Botswana

Ghanzi

15

Trde Pse

Peru

Arequipa

16

Trde Ant

Iran

Jask

17

Trde Normal

Pakistan

Karachi

18

Trhd Normal

Namibia

Mowebaai

19

Mepo Stp

Spain

Tudela

20

Mepo Normal

Chile

Hualpencillo

21

Mepc Stp

Ukraine

Bolgrad

22

Mepc Normal

Tajikistan

Dushanbe

23

Mexo Stp

Argentina

Coronel J.J.Gómez

24

Mexo Normal

Libya

Idris

25

Mexc Stp

Kazakhstan

Pavlodar

26

Mexc Normal

Armenia

Jerevan

27

Medo Stp

Australia

Farina

28

Medo Normal

Egypt

Salum

29

Medc Stp

Kazakhstan

Dzhezkazgan

30

Medc Normal

Uzbekistan

Ak-Baytal

31

Meho Normal

Libya

Gialo

32

Mehc Normal

Iran

Yazd

33

Teho Sbm

New Zealand

Wigram

34

Teho Normal

Ireland

Valentia

35

Teoc Stp

China

Matsu

36

Teoc Sbm

Croatia

Rab

37

Teoc Normal

Uruguay

Artigas

38

Teco Stp

Hungary

Pecs

39

Teco Sbm

India

Srinagar

40

Teco Normal

Byelarus

Brest

41

Texe Stp

Mongolia

Altai

42

Texe Sbm

Ukraine

Kharkov

43

Texe Normal

Argentina

Villa Mercedes

44

Boho Normal

Chile

Navarino

45

Booc Normal

Iceland

Husavik

46

Bosc Stp

Sweden

Bjuroklubb

47

Bosc Normal

Finland

Oulu

48

Boco Stp

Russia

Anavgay Kamchatk

49

Boco Normal

Mongolia

Bulgan

50

Bohc Stp

Russia Yakutskaya

Verkhoyansk

51

Bohc Normal

Russia Yakutskaya

Komara

52

Boxe Stp

USA Alaska

Fort Yukon

53

Poho Normal

Norway

Jan Mayen

54

Pooc Normal

Greenland -DNK-

Ivigtut

55

Poco Stp

Canada

Cambridge Bay

56

Poco Normal

Russia

Yamsk

57

Poxe Stp

Russia Yakutia

Sredne-Kolymsk

58

Poxe Normal

Greenland-Dnk

Umanak

59

Popg Normal

Antarctica

Mcmurdo Station

 

Figure 12.- List of climate-bioclimatic representative examples of almost every combination of Macrobioclimate and Bioclimate / Bioclimatic Variant, with territorial representation on Earth, in alphabetical order of countries.

 

 

Country

Weather Station

Bioclimate/ Variant

59

Antarctica

Mcmurdo Station

Popg Normal

23

Argentina

Coronel J.J. Gómez

Mexo Stp

43

Argentina

Villa Mercedes

Texe Normal

26

Armenia

Jerevan

Mexc Normal

27

Australia

Farina

Medo Stp

5

Bahamas Islands

Nassau Intl

Trps Submesophytic

14

Botswana

Ghanzi

Trxe Normal

40

Byelarus

Brest

Teco Normal

55

Canada

Cambridge Bay

Poco Stp

11

Chad

Ati

Trxe Pse

20

Chile

Hualpencillo

Mepo Normal

44

Chile

Navarino

Boho Normal

3

China

Wucho/Tsang-Wu

Trpl Submesophytic

35

China

Matsu

Teoc Stp

36

Croatia

Rab

Teoc Sbm

28

Egypt

Salum

M