Eco zone

Ecozone is a term used primarily in geoscientific terms for a zonal area of ​​the earth. The eco-zone model enables the mainland to be divided according to several ecological characteristics. Landscapes with a high degree of correspondence between the examined characteristics of climate, vegetation, soils and agricultural uses are combined to form an ecozone. As with all landscape zone models, the classification basically corresponds to the climatic zones as the determining factor, which lie like belts around the earth from the tropics to the two polar zones.

To determine the eco-zones, the visible land forms , the existing ecosystems , the soil types , as well as the agricultural and forestry use systems are used on the basis of the effective climate classification . In addition to these individual features, the typical relationships to one another (such as the material and energy flows) are also taken into account when delimiting the eco-zones. The model primarily follows natural spatial criteria. Cultural spatial aspects are only relevant insofar as there are references to nature. Such references are mostly present in land use, but otherwise tend to be the exception or of lesser importance.

The way we look at the eco-zones is derived from research goals and approaches in geography. The bioecological consideration, which operates with the terms biome or “zonobiom”, comes to quite similar results . The biologists place particular emphasis on the structure of relationships between living beings, while the geographers focus on the abiotic factors.

Terms and history of science

The term ecozone in the sense described here was introduced by Jürgen Schultz (1988).

Similar (mostly older) landscape zone models by other authors are called u. a. Vegetation zones or zonobiome . The partial aspects to which value is placed are in each case different; however, the climate is always a determining factor, as is the soil and vegetation. The plants and their typical formations in particular are receiving more attention: on the one hand, they are relatively easy to grasp and map, on the other hand, a special index function of the plants is assumed. This means that fairly reliable conclusions can be drawn from a plant formation about other factors such as climate and soil, but also existing animals. Since the vegetation changes spatially but at the same time as the other factors, the terms are sometimes used synonymously.

In the English-speaking world, the direct translation of ecozones into ecozones is used in a less differentiated manner by experts. It is also used there for non- geozonal ecoregions (such as the ecozones in the National Ecological Framework for Canada or various “biomes”) as well as for non- climate-related biogeographical regions (such as the flora kingdoms ). In the German-speaking area, the flora and zoogeographical empires in particular are by no means to be equated with the eco-zones.

The German term “Ökozone” is also often used in a very undifferentiated manner outside of the specialist literature. As in English, vegetation zones, zonobiomes, flora-rich, fauna-rich, regional biomes , nature reserves and even small biotopes are designated with it. That has u. a. led to speculation in various forums on the Internet about what exactly an ecozone is.

For the origin and delimitation of the term in the history of science see Geozone

classification

The superordinate unit of the eco-zones is the entire biosphere (sum of all habitats). The eco-zones are a first (possible), rough and large-scale subdivision of the biosphere. Mostly it only refers to the land masses of the earth, since ecological zones in the seas cannot be delimited with the same criteria.

Depending on the author, sub-areas (sub-eco-zones, eco- regions, eco- provinces, eco-districts; biomes ; ecosystem complexes ) are subordinated . The smallest sub-areas that contain a delimitable community are known as biogeozoenoses, which in turn contain individual populations and individuals.

Influences and characteristics

Certain external influences set the framework for the formation of an ecosystem. Their regular global change only leads to the formation of the eco-zones.

Components of landscapes and their relationships with one another

climate

The climate influences all other elements of an ecosystem and comes first in the series of external influencing factors.

The solar radiation increases steadily from the poles to the equator due to the steeper angle of incidence , as does the uniformity of the radiation over the course of the year. The formation of clouds of different strengths results in more complex patterns for global radiation - i.e. the radiation that actually hits the ground. If you subtract reflection and radiation , you get the radiation balance of a place, which in turn determines how much water evaporates and what the temperature curve looks like.

Precipitation is another important factor, both the annual amount of rain and the uniformity of its distribution over the year. Precipitation also influences irradiation and temperature through cloud formation, evaporation and reflection from snow-covered ground.

In addition to the sequence from north to south, there is a typical sequence from the edge to the center of the continents: In the vicinity of the oceans, the climate is more balanced and more humid ( marine climate ), since the temperatures are influenced by the temperature of the sea water. In the interior of the continents it is drier and the temperature fluctuates much more during the year ( continental climate ).

Flora and fauna

The most important plant formations can be derived from the two climatic influencing factors temperature and precipitation, which also form the basis for the models of the vegetation zones and zonobiomes . The eco-zone model builds on these models.

Plants as location-dependent creatures with often only a slow spreading speed are the most obvious indicators of the different ecosystems on earth. There are large deviations within an eco-zone with regard to the equipment with individual plant species or higher taxa . In addition to their ecological requirements, their areas are strongly influenced by the history of the earth, which can be seen in the delimitation of the flora kingdoms . Rather, there is a connection between the eco-zones and plant formations, that is, the vegetation of the different eco-zones has different forms of life and growth .

The larger, more conspicuous animals often have a radius of action that allows them to reach different eco-zones. Well-known examples are migratory birds that fly through all eco-zones during a year and also stay in different zones for longer periods of time. The mass of the species is, however, quite suitable to be viewed in a similar way to the vegetation for differentiating the ecological zones.

Also, the biodiversity can be regionally differentiate simplified specifically, it increases with increasing temperature and moisture at. From this, predictions of the relative diversity of species can be derived for individual eco-zones, which is highest in the humid tropical zone and lowest in deserts and in the polar zones.

ground

Within the large eco-zones there are a multitude of different starting rocks for soil formation , as well as various reliefs . The processes that influence soil formation, however, depend heavily on the climate, as well as on vegetation and animal world, and can therefore just as regularly be assigned to the individual large areas. The weathering of rock in the near-polar zones is largely caused by changes in frost, dead plant remains are only moderately worked into the mineral soil by animals and only slowly decomposed by bacteria and fungi. A litter layer that is not very mixed with the mineral soil is therefore formed on the surface of the soil. In tropical climates, the parent rock quickly weathers due to chemical processes, dead plant remains are quickly worked into the mineral soil by animals and quickly broken down by bacteria and fungi, some of which accumulate as humus in the mineral soil. If humid conditions prevail, certain minerals are washed out (pedal-free soil development), soils with a low pH value are created . In dry zones, soluble salts can accumulate (pedocale soil development), the resulting soils tend to be alkaline . If the plant cover is closed, then the erosion processes by wind and water take place only slowly, chemical over mechanical weathering processes dominate, and the weathering products, together with the organic material accumulating, form a mighty topsoil . Mechanical erosion processes can have a strong effect on gaps in the plant cover. In the different eco-zones, the organisms in the soil have an influence on the decomposition of organic material and its mixing with the weathered parent rock.

Land use is also determined in many places by the characteristic soils, their workability and suitability for use. This in turn intervenes in the natural development of the soil through mechanical soil cultivation and the input of substances.

The FAO (1971–1981) presented a world soil map for the first time . With the accompanying legend, the FAO soil classification was created, which is applicable worldwide. It was replaced in 1998 by the World Reference Base for Soil Resources (WRB). The 2015 update of the third edition of the WRB is currently in use. This enables a global comparison of the soils in the eco-zones.

Dynamics and interrelationships

The material balance of an ecosystem typically changes between the eco-zones: primary production depends largely on factors that were also used above to delimit the zones (size and structure of the vegetation, water supply, temperature, length of the vegetation period). The same applies to the decomposition of the resulting organic matter: temperature and humidity determine whether the soil organisms create a rate of decomposition that reaches production or whether organic matter accumulates in the soil. Depending on the ecozone, fires play a more or less important role in the mineralization of organic matter.

In the course of the year there are characteristic cycles for the material balance. Periods with low temperatures in the eco-zones near the Pole play a major role, and periods with drought in those near the equator. Also succession processes that have longer cycles have evolved differently initialized as by fire in dry zones or wind break in wooded.

The land use of man now represents a defining element, as they nearly global coverage influences the material balance of the ecosystems. If these interventions are linked to an eco-zone, for example in agriculture and forestry, they should be taken into account when describing the eco-zones.

In this context, the two American geographers Erle C. Ellis and Navin Ramankutty developed the model of the " Anthrome " published in 2008 . The term anthrome is an abbreviation for "anthropogenic (= human-influenced) biome". The authors identified 18 different anthromes and divided the remaining unused wilderness areas into three biomes . For the first time, this classification enables a global representation of the current ecological state of the earth.

Problems

Animation: Predicted shift of the climatic zones according to the " worst-case scenario" of the IPCC

Any division of the entire biosphere into a few large areas must be accompanied by rough generalizations. The conditions prevailing at each individual location must be abstracted and averaged so that the actual diversity cannot be represented. Because of this variety of factors that make up a certain ecotope , there is rarely a location that fully corresponds to the description of an ecozone, there are small exceptions and peculiarities everywhere.

Many influences on an ecosystem evade regularity, such as the distribution of rocks, the distribution of sea and land masses or the relief. This creates numerous irregularities that cannot be associated with an ecozone, but rather cause azonal communities. In particular, the height zoning in the mountains overlays the division of the eco-zones, so that a three-dimensional view would be necessary.

The transition from one eco-zone to another (eco- clay ) does not take place abruptly, but gradually with more or less wide transition zones. A cartography, on the other hand, on a global scale, suggests a hard dividing line, the exact location of which has to be determined arbitrarily and therefore varies depending on the author. An ecozone is characterized by many different criteria, which do not necessarily change at the same time, the demarcation therefore turns out differently, depending on which criteria are most important.

The course of the eco-zones has changed again and again over time; during the Ice Age, for example, they were shifted far south. Today's ecosystems in a certain place cannot be explained solely by the environmental conditions that prevail today, but historical developments must be taken into account.

The man-made global warming that is currently taking place will undoubtedly lead to a shift in climatic zones and thus also in eco-zones over the coming decades. As a rule, it will be a north shift (or elevation shift of the elevation steps ).

For more information, see section " Shifting the landscape zones due to climate change "

or → Main article: Consequences of global warming .

The individual eco-zones

Ecological zones of the earth according to Schultz (largely equidistant Eckert VI map projection )

HIGH WIDTH Polar / Subpolar Zone Ice Sheet Tundra Boreal Zone   

MEDIUM-WIDTH Moist medium-widths Dry medium- width deserts and semi-desert grass steppes   

SUBTROPICAL AND EDGE TROPICAL Winter damp Subtropical Always damp Subtropical Tropical / subtropical arid areas Deserts and semi-deserts Winter damp grass and Shrub steppes summer damp thorn savannah u. -stepping     

TROPICAL Summer humid tropics Dry savannah Wet savannah Always humid tropics mountain ranges = black   

Jürgen Schultz has divided his model of eco-zones into nine zones. Other authors do not always orientate themselves on it, so the number of zones and their names can be different. (The FAO model , for example, uses a subdivision into 20 zones and thus comes closer to the classic models of vegetation zones . See map in the article "Landscape zone " )

The distribution of the eco-zones on earth is approximately parallel to the circles of latitude around the earth (broad zonal) and is often spatially isolated from one another ( disjoint ) distributed over the continents . In addition to a further subdivision into sub-zones, a graduation according to height levels is sometimes also carried out.

(The following approximate area proportions refer to the entire land area of ​​the earth. The proportions mentioned by Schultz were recalculated because Greenland and Antarctica were not included.) The proportions of the sub-zones marked with an * were taken from a table of FAO adapted and inserted. The soil names used in the following correspond to the international soil classification system World Reference Base for Soil Resources (WRB) from 2015.

• Polar / Subpolar Zone - 14.8% (10.8% ice-covered areas and polar deserts, and 4.0% tundras)
  The polar and subpolar zone, also known as the Arctic and Antarctic zones, have an arctic and Antarctic climate. Subzones are the ice-covered polar regions, the polar desert and the tundra zone. The treeless tundra grows on humus-rich permafrost soils . If these are mineral, they belong to the cryosols ; if they are organic, they are histosols . The biodiversity is low, many animals are closely tied to the surrounding oceans.
• Boreal Zone - 13.1% (2.6% forest tundra * including open lichen forests in North America and 10.5% boreal coniferous forests *)
  The boreal zone occurs only in the northern hemisphere. In a cold-temperate climate , with cool summers and long winters, there are boreal coniferous forests and large swamps. It can be divided into the three zones of the forest tundra , the open lichen forest and the closed, boreal coniferous forest (taiga). The drier continental areas aredominatedby cryosols , i.e. mineral permafrost soils . Podsols are commonin the more humid oceanic areas. In addition, organic soils ( histosols ) are common, which can occur with or without permafrost. The number of living things and their diversity is small, albeit greater than in the polar zone.
• Moist middle latitudes - 9.7% (4.9% mixed forests * and 4.8% deciduous deciduous forests including temperate rainforests *)
  The nemoral zone, also called temperate zone, humid medium latitudes or humid-temperate zone, occurs in several areas on the Earth before: Europe and Northwest Asia, East Asia, Eastern North America, Western North America; in the southern hemisphere (called the australe zone there) very small sub-areas in Chile and New Zealand. Subzones are the temperate rainforest, the deciduous deciduous forest and the mixed forest on the southern edge of the boreal zone. They are characterized by a climate with moderate frost exposure and sufficient rainfall all year round. Here forests typically grow on Cambisolen or on soils with lessivation , e.g. B. Luvisoles or Alisoles . The biodiversity increases again compared to the boreal zone.
• Dry middle latitudes - 11.1% (8.1% grass steppes and 3.0% temperate semi-deserts and deserts)
  The continental zone or dry middle latitudes have a climate with hot, dry summers and cold winters. Depending on the drought, there is a transition from the forest steppe over grass steppes of different heights to the desert, corresponding soils are Chernozeme , Kastanozeme and Phaeozeme . It is found in North America and Asia in the interior of the continents, in South America and New Zealand in the rain shadow of mountains.
• Winter humid subtropics - 1.7% hard deciduous forests
  The winter humid subtropics, also called the Mediterranean or meridional zone, are hot and dry in summer, humid in winter with little or no frost exposure. Named after the largest sub-area around the Mediterranean Sea, further sub-areas extend in California, central Chile, South Africa (Cape Province) and southwestern Australia. The soils are rich in bases, oftencolored redby hematite, and belong primarily to the Cambisoles and Luvisoles . (Strongly clayey , red Cambisole are called“ Terra rossa ”in the German soil systematics .) Forests of hard deciduous trees( sclerophylls ), which are sensitive to prolonged frost,grow on them. With increasing drought, they change into subtropical shrub and grass steppes with winter rains, whichare commonon calcisoles .
• Always humid subtropics - 4.0% warm-tempered
  humid and laurel forests The ever humid subtropics or laural eco-zones are hardly affected by frost, the rain falls all year round or with a maximum in summer, so there is no lack of water. Acid soils with lessivation , namely alisols and acrisols, are common . They carry an evergreen deciduous forest that is a bit sensitive to frost. These conditions can be found in small areas in the southeast of the continents.
• Tropical / subtropical dry areas - 20.8% (2.3% winter-moist grass and shrub steppes of the subtropics, 6.4% tropical thorn savannahs and steppes, and 12.1% hot semi-deserts and deserts of the subtropics)
  Tropical and subtropical arid areas form the constantly hot deserts. Precipitation can fall at different times of the year, but it is only sufficient for sparse desert vegetation. Ions accumulate in the soil at shallow depths that would be washed out with higher precipitation. If carbonates aredominant, they are calcisols , in gypsum gypsisols , in silicon dioxide durisols and in easily soluble salts Solontschake . Leptosols also occur in the rocky desertand arenosols in the sandy desert. The biodiversity is low here. A subdivision is possible in winter-moist grass and shrub steppes, tropical thorn savannahs and hot deserts.
• Summer humidity tropics - 16.4% (4.4% dry savannas *, 2.6% tropical dry forests * and 9.4% humid savannas)
  Large parts of the tropics have an alternately humid climate with year-round high temperatures and a division into rainy and dry seasons. Tropical deciduous forests or savannas grow here. The soils are often heavily weathered, but relatively alkaline, such as the Lixisole . The diversity and complexity of ecosystems increases rapidly with the available moisture.
• Always-humid tropics - 8.4% tropical rainforests
  In the always-humid tropics there is no division into seasons, it is warm and humid all year round. Evergreen tropical rainforests with the highest biodiversitygrow here. The weathering is relatively rapidly due to the high temperatures and the large water resources. In regions that have had little ore formation and erosion for a long time, the soils are also very old. This applies above all to the equatorial lowlands of Africa and South America, in which ferralsoles are widespread, i.e. soils that are dominated by the clay mineral kaolinite , which can hardly store nutrients. Agriculture without intensive fertilization therefore leads to rapid nutrient depletion.

literature

• Jürgen Schultz: The earth's eco-zones. Ulmer, Stuttgart 2016 (5th edition) ISBN 978-3-8252-4628-0
• Jürgen Schultz: Eco zones . Ulmer. Stuttgart 2010 ISBN 978-3-8252-3424-9
• G. Grabherr: Color Atlas of Earth's Ecosystems . Ulmer, Stuttgart 1997 ISBN 3-8001-3489-6
• Hermann Remmert : Special ecology. Terrestrial systems. Springer, Berlin 1998 ISBN 3-540-58264-9
• M. Richter: Vegetation Zones of the Earth. Klett-Perthes, Gotha 2001 ISBN 3-623-00859-1
• W. Frey, R. Lösch: Textbook of Geobotany . Gustav Fischer, Stuttgart 1998 ISBN 3-437-25940-7
• J. Pfadenhauer, F. Kötzli: Vegetation of the earth. Springer Spectrum, Heidelberg 2014. ISBN 978-3-642-41949-2 .
• W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the world. 2nd Edition. Springer Spectrum, Heidelberg 2014. ISBN 978-3-642-36574-4 .

Web links

Commons : Ecozones  - collection of pictures, videos and audio files

• Diercke World Atlas of Eco Zones

Individual evidence

1. ↑ Kehl, H .: "Vegetation Ecology Tropical & Subtropical Climates / LV-TWK (B.8) - TU Berlin"
2. ↑ Anselm Kratochwil, A. Schwabe: Ökologie der Lebensgemeinschaften . Biocenology. Ulmer, Stuttgart 2001, pp. 75-76. ISBN 3-8252-8199-X
3. ^ H. Haeupler: The biotopes of Germany . In: Federal Agency for Nature Conservation (Ed.): Series of publications for vegetation science . No. 38 , 2002, ISSN  0085-5960 , p. 247 f .
4. ↑ FAO-UNESCO (ed.): Soil Map of the World . 11 volumes. 1: 5 million UNESCO, Paris 1971–1981.
5. ↑ FAO-UNESCO: Soil Map of the World. Legend . UNESCO, Paris, 1974.
6. ↑ ^{a b} IUSS Working Group WRB: World Reference Base for Soil Resources 2014, Update 2015 . World Soil Resources Reports 106, FAO, Rome. 2015.
7. ↑ Alder C Ellis u. Navin Ramankutty Putting people in the map: anthropogenic biomes of the world. The Ecological Society of America , Washington DC 2008.
8. ^ "Global Ecological Zoning for the global forest resources assessment" 2000
9. ↑ J. Schultz: The ecological zones of the earth. Ulmer, Stuttgart 2008, ISBN 978-3-8252-1514-9
10. ^ "Global Ecological Zoning for the Global Forest Resources Assessment" 2000. FAO, Rome 2001