Boreal ecosystem

  • Boreal zone

The boreal zone is one of the nine global ecozones by J. Schultz. Today it occupies about 13.1% of the terrestrial land surface. Beginning of the 21st century of which are still about 70 % in a largely natural state.

Your expansion coincides approximately with the cold temperate zone. The prevailing vegetation it can still be broken down into the types of landscape forest tundra and Boreal Forest.

The boundaries of the boreal zone are fluent in reality, so that an exact expansion - as marked on the map - in fact can not be set. This fact can be understood if one uses similar geozonale models that have significant deviations in some cases. Consider this example, the comparable Boreale Zonobiom on the map of Zonobiome by Walter and Breckle or FAO ecozones.

In the north the boreal zone ends at the polar timberline to the forest-tundra before it merges with the Polar / Subpolar ecozone. In the south, bordering the temperate broadleaf and mixed forests of the humid mid-latitudes or the steppes of dry mid-latitudes. The ecosystem of the boreal zone includes the largest contiguous forests in the world and spans about 2 billion hectares.

The term boreal zone is derived from ancient Greek boreas βορέας what " cold " means and at the same time refers to Boreas, the Greek god of the wintry north wind.

  • 4.1 fauna
  • 4.2 wildlife


The boreal zone spans the northern hemisphere of the earth quite regularly with about 700 to 2000 km wide band. In Eurasia extending from Norway across Siberia to Kamchatka, in North America from Alaska across Canada to Newfoundland. Respectively on the western sides of the continents, so in Norway and the North American Pacific coast, the occurrence is further north pushed by warm ocean currents as on the East Coast.

To the north, the polar tree line limits the boreal zone, however, no sharp dividing line, but a several tens of kilometers wide ecotone. The forests are there always lights, forest and tundra change like a mosaic and form the so-called forest-tundra, to the treeless tundra followed. The climate of the northern edge of the boreal zone roughly coincides with the 10 - together ° C July isotherm. On the Taimyr peninsula in Russia, the boreal zone reaches up to 70 ° N, on Hudson Bay it is already at 55 ° N on the tundra.

To the south are close to the mid-latitudes, which can be pronounced depending on the amount of rain as forest or steppe. Again, the transition is not abrupt, but coniferous forest and deciduous forest, and coniferous trees and forest- steppe free merge. Approximately six months, the vegetation period must last, so that one speaks of the warm temperate zone: north of it is in the boreal zone, speaking boldly, the winter more than the summer. After AGENTS the southern boundary of the boreal zone roughly coincides with the 18 - together ° C July isotherm.

In the southern hemisphere there are areas that would be climatically similar, almost exclusively in the sea. In the extreme south of South America and New Zealand and the subantarctic islands there are some similarities, but the differences in climate and ecology are so large that you do not speak here of a boreal zone.


The boreal zone and the mountainous regions of the warm temperate zone are collectively referred to as boreomontan. As well as the boreal zone and the higher mountain regions of the warm temperate zone were originally almost completely covered by coniferous forest, with numerous climatic and ecological similarities and common flora and faunal elements, the term " boreomontan " appeared to the similarities of the two spatially to appoint separate coniferous forest regions.


Main article: Cold Temperate Climate

The cold- temperate climate is characterized by long, cold winters and short, moderately warm summers. The temperatures reach minimum values ​​down to -40 ° C in winter in the interior of the continents ( down to -70 ° C in the continental Siberia ) and get in the summer for two to three months at mean temperatures above 10 ° C. Pretty much the climate is determined by the arctic cold air - in winter the Arktikfront often lies on the southern edge of the boreal zone, while warmer air currents of the Pacific or Atlantic are determinative in the summer. The vegetation period is usually four to five months. Less still, but also warmer, the summers are in the continental climate, under oceanic influence of the summer is longer, but is also cooler. If the average temperature below 0 ° C, permafrost forms, however, the boundary of the permafrost is not identical with the limit of the boreal zone.

The precipitates move on average in most areas between 250 and 500 millimeters, which initially very little appears. Due to the low evaporation but almost never a shortage of water ( humid climate ). In addition, thawing snow still long water supply those on permafrost and water can not seep. The rain usually predominates slightly against the snow shares, the snowpack remains are up to seven months.

During the summer reign long-day - period to day conditions. The day lengths achieve this in the time of summer solstice on the southern border and 16 on the northern border 24 hours. Thus, the low intensity of solar radiation can be compensated at least for some time. The air temperature is still very low, because the energy for the melting of snow and ice is consumed.

The temperature differences between regions within the boreal zone can be very high due to different continentality or oceanity. The cold continental climate type, for example, occurs in the Siberian taiga, is extremely cold winters, where the temperature can drop to -70 ° C. This is offset by relatively warm, short summers with maximum temperatures of 30 ° C. The annual average temperature there is very low at -10 ° C. This continental locations of the boreal zone have the highest temperature amplitudes. The cold oceanic climate type, for example, from southern Alaska and Norway, however, has slightly cooler summer, but also milder winters. The temperature amplitudes are not so high, the mean annual temperatures higher. The snow thickness and in general the rainfall is higher here.

Small-scale micro-climates can have a large effect on the ecosystem. Even small slope angles change the radiation balance significantly in the prevailing low sun positions and lead to different conditions on the North and south facing slopes.


Vast landscapes of the boreal zone are formed of old continental shields that have experienced no changes by plate tectonics or volcanism in a long time. Due to the long-term erosion of the relief energy is low, flat plains and hill country dominate. The rocks provide in weathering acidic, nutrient-poor soils. More recent are in North America, the Rocky Mountains, in Asia, the Urals and the East Siberian mountain country. During the ice ages, large parts of glaciers were covered superficially and were shaped by the ice flow, soil formation continued so until fairly recently a.

The winter frost plays a major role in soil formation. Permafrost is widespread in summer with different thaw depths. The expansion upon freezing up surveys form, thaws the ground, lowering form. The regular ground movements ( Kryoturbation ) to ice wedges and frost -patterned ground form, as they still occur in the tundra pronounced. Whether forms permafrost or how deep the soil thaws can be affected by small changes in the environmental conditions, so that takes place a frequent change of soil conditions. In the forest, the sun heats mainly the crown area, the ground comes to little heat, it remains the only superficial thawing permafrost. In forest-free, cleared or burned areas of deeper soil thaws on and bagged a through nachfließendes water the radiation absorption and heat storage is increased - it forms a lake ( thermokarst, Alass ). The reverse process occurs: a silted lake, isolated vegetation the ground, then the summer heat will be lower and the advancing permafrost transforming the lake into a bulging mound of ground ice ( pingo, Bulgunnjacha ).

Due to the low seepage and evaporation or prolonged frost at greater depths it comes to waterlogging.

In those cold, wet and acidic conditions, the resulting scattering decomposes only very slowly with the release of humic acids. It forms with the time on the mineral soil, a thick Rohhumusschicht; because soil organisms are rare, it is the ground on almost unmixed. Nutrients are mineralized only slowly and are poorly available to plants. The pH of the soil and the diffusion layer is lowered below 5.5, whereby the nutrients are dissolved and the H ions are bound. In the upper soil layers dissolve clay minerals, aluminum and iron oxides, which precipitate back into deeper soil layers. This podsolization called process leads to the formation of a nutrient-poor, highly acidic bleach topsoil ( A horizon ), where a hard, impermeable B- horizon ( " B " on the right) follows. The result is a podzol, which is quite unfavorable for plants: nutrients were washed out by the low pH, the water capacity is low and limited to the root zone through the hardened layer of soil. In a very base-rich mineral soils under the podsolization remains, nevertheless, a undecomposed litter layer, which mixes little with the ground, the resulting soil is called Cambisol forms.

At places where water can drain away bad where ground water is present greater than about 50 inches below the ground surface, is formed from dead plants peat. A thin layer of peat can also form in wooded areas in the boreal zone, from the thickness of the peat layer 20 to 30 centimeters is called a Moor.

Plants and Animals

The biodiversity in the boreal zone, compared with more southern ecosystems, low. Long stretches of individual plant species dominate the picture, conifers of the family Pinaceae - throughout the boreal zone is essentially only twenty different species of trees. For shrubs or perennials in the understory generally very little is left of light and nutrients. The ecological relationships between organisms are not very specialized, represented herbivorous insects with only a few species.

Plant world

Main article: Boreal Forest, Moor

Coniferous forests and bogs determine the flora. Conifers of the genera spruce, fir, larch and pine form part mixed, but often mono- dominant stands. The trees are wind pollinated and spread their seeds mostly by the wind. The holdings reach a height of about twenty meters, the trees do not compete so much about the light as the nutrients in the soil. The high nutrient requirements of deciduous trees around each spring to form new leaves is also seen as crucial to the dominance of conifers. In addition, the Evergreen able to exploit the short growing season better. ( In Asia, the boreal forest limit, however, of the deciduous Dahurischen larch (Larix gmelinii ) is formed, which dominates in eastern Siberia to wide open spaces. ) In the shrub layer, there are deciduous trees, mainly birches, poplars, willows and alder trees. Here comes more frequently pollination and seed dispersal by animals before, such as haws, Snowball, cloudberry, Swedish National dogwood and the various dwarf shrubs of the family Ericaceae, such as the blueberry. Close to the ground are still growing mosses and lichens, they are more common than vascular plants in the herb layer. Fungi are present in large quantity, all woody plants form a symbiosis with them ( mycorrhiza ).

Moore are widespread in the boreal zone, because the soils are strongly affected by standing water and organic matter decomposes slowly. Their area ratio is on average 20 to 30%, but may increase to over 50%. Forests with anmoorigem soil and forest-free moorland flow smoothly into one. The bogs are interspersed with many open water areas, marshes and waters are nutrient poor ( oligotrophic ). The growth rates of the peat layer are less than a millimeter per year, in the northern area even values ​​of only 0.2 millimeters per year can be achieved. Nevertheless, through the huge surface area, a significant amount of carbon in the boreal peatlands is stored.

Deciduous forests are common in the boreal zone only a few places. Individual deciduous trees, such as birch and poplar are indeed represented everywhere in the coniferous forests, but real hardwood forests form only in strongly oceanic embossed Scandinavia and Kamchatka, where birch trees form the boreal forest limit. In floodplains and more favored locations they can occur anywhere in the boreal zone and form possible, interspersed with Hochstaudenfluren grove.

The taper or alteration of ecosystems is often done on larger areas in common: events such as forest fires, storm damage to the shallow thawing soils, flooding or siltation, damage by animals capture the woods so frequently that the trees do not usually reach their maximum age, but dieback and replaced with a new generation. The herb - and shrub -rich succession areas are an important habitat for many animal and plant species. Especially by forest fires, the accumulated litter is mineralized and on the nutrient-rich, sunny ashes grow perennials and deciduous shrubs.


The animal population is low by both the number of species as well as individuals. The dominant coniferous forests and bogs provide little food, are slightly cheaper, the deciduous forests and succession areas sporadic. Well-known species, which have their distribution in the boreal zone are moose, brown bear, arctic hare, wolverine, lynx and marten different. Due to the strong winter all animals have developed appropriate adjustments: Many birds migrate south, mammals and insects hold a winter rest or are active under the protective blanket of snow. Reptiles and amphibians are largely absent, as well as larger soil organisms - dead organic matter is usually decomposed by fungi.

Land use

Despite its wealth of natural resources, the use of this zone is limited due to the harsh climatic conditions. The action by the people here is so comparatively low. The main land use type is the logging, in addition, there are resin and honey extraction and mining of peat, the traditional fur animal hunting and gathering of wild berries. The extraction of mineral resources is complicated by the difficult transport conditions and permafrost. Agriculture (such as rye, barley, oats and potatoes) and grazing have because of the climate and less fertile soils barely importance only to ensure the self-sufficiency of the local population.

The input of nutrients by winds affects the nutrient-poor waters and actually Moore, the formerly clear lakes turbid by stronger growth of algae, silt and peat run faster. Since the very sensitive lichens are an important part of the undergrowth, to industrial emissions and material inputs affect mining areas a noticeable effect on the boreal zone.

By logging in the boreal forests about 90 % of global demand for paper and lumber are covered. However, the forestry yield is low because the growth benefits are low in the cold climate. In commercial use of wood, there are many problems: the remoteness and size of areas leads to long transport routes. Through sparse trees, there is little usable wood mass per area. Due to low temperatures and high snow cover in winter the wood quality is low, because the plant height is very low. The wood can usually only be used for the production of paper, or as fuel, and the reforestation or natural regeneration lasts relatively long. Therefore, losses are now through deforestation and peat sprung up everywhere.