Vegetation zone (also Florenzone , but not Florenreich ) is a term from geobotany and landscape or vegetation geography for a geozonal large area of the earth whose naturally occurring plant formations on the global scale level due to certain similarities to a large-scale ecosystem or landscape type (e.g. a certain, large-scale dominant forest or open land type ) is summarized.
In this determination, it is irrelevant whether or not closely related species of specific plant communities are involved (the family relationships based on a common evolution of the plant world are geographically referred to as flora kingdoms). Instead, similar adaptation strategies of different species to the prevailing climate are decisive for the vegetation zones . Accordingly, the vegetation zones in the narrower sense reflect the earth's climatic zones , which lie like belts around the earth from the tropics to the two polar zones. In contrast to the very similar climate zone maps of the so-called effective climate classification , vegetation zone models are based more on observation data than on measured values.
If the entire earth were a completely flat land mass without oceans and mountains, the climate and vegetation zones would run completely straight and parallel around the earth. In reality, however, the oceans in particular (as the main source of precipitation distribution) have a major influence on the climate and ensure that the zones are more irregular. Accordingly, the vegetation also deviates from the broad zonal lines and is either more oceanic or more continental . However, not all models of vegetation zones show these differences. Within the zones or across zones, there is altitude-dependent vegetation (see altitude level ), so that the upper limit of the zonal vegetation (depending on the local climatic conditions) is between 500 and 1500 meters above sea level .
Delimitation of the term
In contrast to the more recent concepts of zonobiome or eco-zones , it is more related to vegetation than to climate. In the literature, however, these (and other) terms are often used synonymously. However, you can usually tell from the number of different zones and formations which model is involved. If more than 20 different types are differentiated, vegetation zones are shown, even if the terminology sometimes suggests something different . A good example are the FAO's “Ecozones” (see map in the Landscape Zone article ), which should not be confused with the German model of “Ecozones” .
Basics and the problem of drawing boundaries
The starting point for the division of the zones is always the potential natural or climax vegetation that would develop in a delimitable area without human influence. Cultural spatial aspects that are included in the eco-zone model to a certain extent are not relevant here. To define the zones, neighboring plant locations with close interrelationships are grouped together to form larger units, the " plant formations ". Then the formations of the same climatic zone are combined to form even larger "large formations". Here, the commonalities lie primarily in the similar strategies of adaptation of the “leading vegetation” to the prevailing climate. If necessary, a further summary is made to finally arrive at a vegetation zone. The standard work Atlas on Biogeography by Schmithüsen shows 154 different plant formations in the continent maps, which have been merged into 30 zonal biome types on the world map.
|1||Biotopes: Different types of beech forest in Europe + stream and river meadows + interspersed bodies of water and moors, etc.||Plant formation "Summer green beech forests of Europe"|
|2||+ similar forests in North America Asia||Plant formation "Summer green forests of the northern hemisphere"|
|3||+ similar forests in the southern hemisphere||Plant formation "deciduous deciduous forests of the temperate climate zone"|
|4th||+ Plant formation "evergreen temperate deciduous forests"||Vegetation zone "deciduous forests of the temperate zone"|
The aforementioned method inevitably leads to a considerable (deliberate) simplification of the map image ( generalization ) in every step of the summary and due to the large scale . In addition, there is the fundamental problem of the necessary “artificial” demarcation between plant formations, which in reality naturally merge into one another (for more details see under landscape zone ).
The sequence of different climates , structured from north to south, goes back to the spherical shape of the earth and is the basis of all geozonal models. The climate influences all other elements of an ecosystem and comes first in the series of external influencing factors. Modern zone concepts use effective climate classification , which provides data on the annual course of temperatures and the frequency, distribution and amount of precipitation. The most important plant formations and biome types can be derived from these climatic influencing factors :
> 10 ° C
|Annual precipitation (mm)|
|up to 125||up to 250||up to 500||up to 1000||until 2000||over 2000|
|0||Lichen Tundra||Dwarf trauma tundra||Meadow tundra|
|1 to 4||Deciduous coniferous forest||Evergreen coniferous forest||Deciduous deciduous forest|
|5 to 7||desert||Desert steppe||steppe||Deciduous deciduous forest||Temperate rainforest|
|8 to 12||desert||Semi-desert||Dornsteppe||Hard foliage vegetation||Subtropical rainforest|
|12||desert||Semi-desert||Thorn savannah||Dry savannah||Moist savannah||Tropical rain forest|
In addition to the sequence from north to south, there is a gradient from the edge to the center of the continents: near the oceans the climate is more balanced and more humid ( marine climate ), the temperatures are influenced by the temperature of the adjacent water. In the interior of the continents it is drier and the temperature fluctuates much more during the year ( continental climate ).
Non-zonal plant formations
Not all the observed plant occurrences can be brought into agreement with the concept of vegetation zones: Occasionally, exceptional external conditions are effective at a location, which give rise to azonal or extrazonal vegetation . This applies particularly noticeably and extensively to the extrazonal vegetation of the mountains.
In addition, there are other non-zonal formations such as reed areas in floodplains, salt marshes on the coasts, salt lakes and a few more.
The current spatial distribution of plants also reflects the geological development of the continents . This different development history of the plants in separate areas is caused by the flora - not by vegetation zones! - detected.
Shift through epochs of climate change
The present day vegetation zones were on the northern hemisphere of the earth (primary both sides of the Atlantic ) during the climate change, the ice age moved far to the south. The course of the vegetation belts and their shift back to their present postglacial position had a decisive influence on the development of mankind towards the Neolithic .
The man-made global warming that is currently taking place will undoubtedly lead to a renewed shift in climate and vegetation zones over the coming decades. As a rule, it will be a north shift (or elevation shift of the elevation steps ).
The vegetation zones of the earth
The following map "Vegetation zones and non-zonal plant formations" shows in great detail 26 delimitable vegetation zones and 14 non-zonal large plant formations of the earth.
- Polar climates (approx. 16%) with the ice sheets (approx. 9%) , the polar cold deserts with almost no vegetation (approx. 1%) and the tundras (approx. 5%) , which are broken down into two different types on the map are. While around 80% of the ice sheets are in the Antarctic in the southern hemisphere, 99% of the tundras are in the northern Arctic . Other ice areas ( glaciers , approx. 0.2% ) and vegetation-free cold deserts (approx. 1%) lie outside the polar regions (extrazonal) in the high mountains of the earth. Due to the similarities of the plant cover, the map summarizes the extrazonal alpine mats and heaths of other climatic zones with the Nordic mountain tundra (approx. 2%) . The two extrazonal types of the total zonal forest tundra and the azonal subpolar meadows, heaths and moors (approx. 3%) of the subarctic lead over to the boreal forests (except for the “ Magellanic tundra ” of southernmost South America).
- Cold temperate boreal coniferous forest zone (approx. 9%) with the azonal evergreen coniferous forests (approx. 6%) and the deciduous ( larch ) coniferous forests of Eastern Siberia (approx. 3%) , which also only occur in the northern hemisphere.
Cool-temperate climate zone (approx. 19%) : The winters are milder and shorter here than further towards the poles, the length of the vegetation period increases accordingly. The vegetation here is decisively shaped by the availability of water, i.e. the amount and frequency of precipitation or the distance from the sea. One can therefore distinguish three areas within the cool temperate zone:
- Zone of winter bare and deciduous deciduous and mixed coniferous forests (approx. 7%) , in which water does not become a deficiency factor, i.e. it is available all year round. In the transition from the boreal forests they are often developed as mixed deciduous and coniferous forests (approx. 2%) . The wooded floodplains of the temperate deciduous and alluvial forests (approx. 6%) with their deciduous trees on the rivers extend far into the steppe zone. Forests with evergreen deciduous trees on the southern edge of the temperate zone are usually included in the summer green deciduous forests. Under high ocean conditions, evergreen temperate coastal rainforests (approx. 0.5%) , such as B. on the American west coast (British Columbia and Chile). Their assignment to the zones or extrazonal formations is inconsistent.
- Zone of the steppes (approx. 8%) , which are divided into the mixed forest steppes (approx. 2%) , grass steppes and salt marshes (approx. 2%) as well as shrub u. Dry steppes (approx. 4%) are subdivided. (The salt marshes listed with represent a non-zonal plant formation of a small area, which was only combined with the grass steppes due to their steppe-like character).
- Zone of winter-cold semi-deserts and deserts (approx. 3%) in the interior of the continents with strong heat-cold extremes and very little precipitation. Here - as in the tundra - no tree growth is possible. In the northern hemisphere, the greater proportion is in the semi-deserts (approx. 2%) . About half of the winter-cold deserts (approx. 1%) are almost without vegetation. Around 95% of these extremely hostile areas are in Central Asia.
Subtropical climatic zone (approx. 19%)
- Zone of evergreen hard-leaf vegetation (approx. 2%) (especially on the western side of the continents). This zone is under the influence of cyclonic westerly winds, but in summer also under the influence of subtropical high pressure zones. (The area of the hardwood forests around the Mediterranean is sometimes also referred to as the Mediterranean zone ).
- Zone of the (predominantly) subtropical (hot) semi-deserts and deserts (approx. 14%) (extremely arid climate ). In contrast to the winter-cold deserts and semi-deserts, the proportion of semi-deserts is lower everywhere except for Australia (approx. 6%) . About a quarter of the hot deserts (approx. 9%) is almost without vegetation. Around 60% of these inhospitable areas are in the Sahara , around 30% in the adjoining desert regions of the Middle East. Only about 1% of the Australian desert areas are completely free of vegetation.
- Zone of subtropical moist forests or laurel forests . (approx. 2%) These are evergreen deciduous forests with warm and humid climates (often on the east side of the continents with heavy monsoon rain in summer and high temperatures; also in summer dry and winter humid climates, when regular cloud formation weakens the summer dryness.)
- A few rain-green moist forests and rainforests in the tropical zone extend into the subtropics and are only slightly different there. They are therefore sometimes designated separately as subtropical rainforests . (together approx. 0.4%)
Tropical climate zone (approx. 30%)
- (Deciduous) zone of the dry bare and the part-evergreen savannah (about 13%) , identified by the dry savannah (approximately 3%) over the Dornstrauch- and cacti savannah (about 5%) to the rain green humid savannah (ca. 5 %) occupy a large part of the tropics .
- Zone of the rain-green wet forests (approx. 3%) , which lead from the savannas to the tropical rainforests and partly consist of seasonally deciduous trees.
- Zone of tropical dry forests (approx. 4%) in which there are extensive periods of drought.
- Zone of the evergreen tropical rainforests (approx. 9%) .
For all other areas on the map: temperate and subtropical mountain forests as well as tropical clouds and cloud forests up to the subalpine tree line (approx. 1% each), highland steppes and deserts (approx. 1% - mainly in the Tibetan highlands and in the Andes ), reed swamps and flood water plants (about 0.5%), oases vegetation (larger surfaces exclusively in the Sahara, here about 2%) and mangrove coastal is not more zonal plant formations.
In the southern hemisphere , zones 7–3 and 1 follow in reverse order. Zone (2), covered by boreal coniferous forest in the northern hemisphere , lies in the southern hemisphere largely in the strip covered by the oceans and is absent on land.
- Anton Fischer: Forest vegetation science. Blackwell, Berlin, Vienna a. a. 1995, ISBN 3-8263-3061-7 .
- R. Pott: General geobotany. Berlin / Heidelberg 2005, ISBN 3-540-23058-0 , pp. 353-398.
- M. Richter: Vegetation Zones of the Earth. Klett-Perthes-Verlag, Gotha 2001, ISBN 3-623-00859-1 .
- Martin Schaefer: Dictionary of Ecology. 4th edition. Spectrum, Berlin 2003, ISBN 3-8274-0167-4 .
- J. Schmithüsen (Ed.) Atlas of Biogeography. Meyer's large physical world atlas, volume 3. Bibliographical Institute, Mannheim / Vienna / Zurich 1976, ISBN 3-411-00303-0 .
- Richard Pott: General Geobotany. Springer, Berlin / Heidelberg 2005, ISBN 3-540-23058-0 .
- Dieter Heinrich, Manfred Hergt: dtv atlas for ecology. 3. Edition. German Taschenbuch-Verlag, Munich 1994, ISBN 3-423-03228-6 (dtv 3228).
- Jörg S. Pfadenhauer and Frank A. Klötzli: Vegetation of the earth. Springer Spectrum, Berlin / Heidelberg 2014, ISBN 978-3-642-41949-2 . P. 73.
- Global Ecological Zoning for the global forest resources assessment 2000 . Rome 2001
- J. Schmithüsen (Ed.): Atlas for Biogeography. Meyer's large physical world atlas, Volume 3, Bibliographisches Institut, Mannheim, Vienna, Zurich 1976. ISBN 3-411-00303-0 .
- Table from Schultz, 2000, pp. 45–46 and Post u. a., 1982 in: Schultz, 2000, p. 35.
- The names and proportions were determined when the vegetation zones map was drawn up , listed in a table and extensively verified. See sources there